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# sql/selectable.py
# Copyright (C) 2005-2024 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: https://www.opensource.org/licenses/mit-license.php
"""The :class:`_expression.FromClause` class of SQL expression elements,
representing
SQL tables and derived rowsets.
"""
from __future__ import annotations
import collections
from enum import Enum
import itertools
from typing import AbstractSet
from typing import Any as TODO_Any
from typing import Any
from typing import Callable
from typing import cast
from typing import Dict
from typing import Generic
from typing import Iterable
from typing import Iterator
from typing import List
from typing import NamedTuple
from typing import NoReturn
from typing import Optional
from typing import overload
from typing import Sequence
from typing import Set
from typing import Tuple
from typing import Type
from typing import TYPE_CHECKING
from typing import TypeVar
from typing import Union
from . import cache_key
from . import coercions
from . import operators
from . import roles
from . import traversals
from . import type_api
from . import visitors
from ._typing import _ColumnsClauseArgument
from ._typing import _no_kw
from ._typing import _TP
from ._typing import is_column_element
from ._typing import is_select_statement
from ._typing import is_subquery
from ._typing import is_table
from ._typing import is_text_clause
from .annotation import Annotated
from .annotation import SupportsCloneAnnotations
from .base import _clone
from .base import _cloned_difference
from .base import _cloned_intersection
from .base import _entity_namespace_key
from .base import _EntityNamespace
from .base import _expand_cloned
from .base import _from_objects
from .base import _generative
from .base import _never_select_column
from .base import _NoArg
from .base import _select_iterables
from .base import CacheableOptions
from .base import ColumnCollection
from .base import ColumnSet
from .base import CompileState
from .base import DedupeColumnCollection
from .base import Executable
from .base import Generative
from .base import HasCompileState
from .base import HasMemoized
from .base import Immutable
from .coercions import _document_text_coercion
from .elements import _anonymous_label
from .elements import BindParameter
from .elements import BooleanClauseList
from .elements import ClauseElement
from .elements import ClauseList
from .elements import ColumnClause
from .elements import ColumnElement
from .elements import DQLDMLClauseElement
from .elements import GroupedElement
from .elements import literal_column
from .elements import TableValuedColumn
from .elements import UnaryExpression
from .operators import OperatorType
from .sqltypes import NULLTYPE
from .visitors import _TraverseInternalsType
from .visitors import InternalTraversal
from .visitors import prefix_anon_map
from .. import exc
from .. import util
from ..util import HasMemoized_ro_memoized_attribute
from ..util.typing import Literal
from ..util.typing import Protocol
from ..util.typing import Self
and_ = BooleanClauseList.and_
_T = TypeVar("_T", bound=Any)
if TYPE_CHECKING:
from ._typing import _ColumnExpressionArgument
from ._typing import _ColumnExpressionOrStrLabelArgument
from ._typing import _FromClauseArgument
from ._typing import _JoinTargetArgument
from ._typing import _LimitOffsetType
from ._typing import _MAYBE_ENTITY
from ._typing import _NOT_ENTITY
from ._typing import _OnClauseArgument
from ._typing import _SelectStatementForCompoundArgument
from ._typing import _T0
from ._typing import _T1
from ._typing import _T2
from ._typing import _T3
from ._typing import _T4
from ._typing import _T5
from ._typing import _T6
from ._typing import _T7
from ._typing import _TextCoercedExpressionArgument
from ._typing import _TypedColumnClauseArgument as _TCCA
from ._typing import _TypeEngineArgument
from .base import _AmbiguousTableNameMap
from .base import ExecutableOption
from .base import ReadOnlyColumnCollection
from .cache_key import _CacheKeyTraversalType
from .compiler import SQLCompiler
from .dml import Delete
from .dml import Update
from .elements import BinaryExpression
from .elements import KeyedColumnElement
from .elements import Label
from .elements import NamedColumn
from .elements import TextClause
from .functions import Function
from .schema import ForeignKey
from .schema import ForeignKeyConstraint
from .sqltypes import TableValueType
from .type_api import TypeEngine
from .visitors import _CloneCallableType
_ColumnsClauseElement = Union["FromClause", ColumnElement[Any], "TextClause"]
_LabelConventionCallable = Callable[
[Union["ColumnElement[Any]", "TextClause"]], Optional[str]
]
class _JoinTargetProtocol(Protocol):
@util.ro_non_memoized_property
def _from_objects(self) -> List[FromClause]: ...
@util.ro_non_memoized_property
def entity_namespace(self) -> _EntityNamespace: ...
_JoinTargetElement = Union["FromClause", _JoinTargetProtocol]
_OnClauseElement = Union["ColumnElement[bool]", _JoinTargetProtocol]
_ForUpdateOfArgument = Union[
# single column, Table, ORM Entity
Union[
"_ColumnExpressionArgument[Any]",
"_FromClauseArgument",
],
# or sequence of single column elements
Sequence["_ColumnExpressionArgument[Any]"],
]
_SetupJoinsElement = Tuple[
_JoinTargetElement,
Optional[_OnClauseElement],
Optional["FromClause"],
Dict[str, Any],
]
_SelectIterable = Iterable[Union["ColumnElement[Any]", "TextClause"]]
class _OffsetLimitParam(BindParameter[int]):
inherit_cache = True
@property
def _limit_offset_value(self) -> Optional[int]:
return self.effective_value
class ReturnsRows(roles.ReturnsRowsRole, DQLDMLClauseElement):
"""The base-most class for Core constructs that have some concept of
columns that can represent rows.
While the SELECT statement and TABLE are the primary things we think
of in this category, DML like INSERT, UPDATE and DELETE can also specify
RETURNING which means they can be used in CTEs and other forms, and
PostgreSQL has functions that return rows also.
.. versionadded:: 1.4
"""
_is_returns_rows = True
# sub-elements of returns_rows
_is_from_clause = False
_is_select_base = False
_is_select_statement = False
_is_lateral = False
@property
def selectable(self) -> ReturnsRows:
return self
@util.ro_non_memoized_property
def _all_selected_columns(self) -> _SelectIterable:
"""A sequence of column expression objects that represents the
"selected" columns of this :class:`_expression.ReturnsRows`.
This is typically equivalent to .exported_columns except it is
delivered in the form of a straight sequence and not keyed
:class:`_expression.ColumnCollection`.
"""
raise NotImplementedError()
def is_derived_from(self, fromclause: Optional[FromClause]) -> bool:
"""Return ``True`` if this :class:`.ReturnsRows` is
'derived' from the given :class:`.FromClause`.
An example would be an Alias of a Table is derived from that Table.
"""
raise NotImplementedError()
def _generate_fromclause_column_proxies(
self, fromclause: FromClause
) -> None:
"""Populate columns into an :class:`.AliasedReturnsRows` object."""
raise NotImplementedError()
def _refresh_for_new_column(self, column: ColumnElement[Any]) -> None:
"""reset internal collections for an incoming column being added."""
raise NotImplementedError()
@property
def exported_columns(self) -> ReadOnlyColumnCollection[Any, Any]:
"""A :class:`_expression.ColumnCollection`
that represents the "exported"
columns of this :class:`_expression.ReturnsRows`.
The "exported" columns represent the collection of
:class:`_expression.ColumnElement`
expressions that are rendered by this SQL
construct. There are primary varieties which are the
"FROM clause columns" of a FROM clause, such as a table, join,
or subquery, the "SELECTed columns", which are the columns in
the "columns clause" of a SELECT statement, and the RETURNING
columns in a DML statement..
.. versionadded:: 1.4
.. seealso::
:attr:`_expression.FromClause.exported_columns`
:attr:`_expression.SelectBase.exported_columns`
"""
raise NotImplementedError()
class ExecutableReturnsRows(Executable, ReturnsRows):
"""base for executable statements that return rows."""
class TypedReturnsRows(ExecutableReturnsRows, Generic[_TP]):
"""base for executable statements that return rows."""
class Selectable(ReturnsRows):
"""Mark a class as being selectable."""
__visit_name__ = "selectable"
is_selectable = True
def _refresh_for_new_column(self, column: ColumnElement[Any]) -> None:
raise NotImplementedError()
def lateral(self, name: Optional[str] = None) -> LateralFromClause:
"""Return a LATERAL alias of this :class:`_expression.Selectable`.
The return value is the :class:`_expression.Lateral` construct also
provided by the top-level :func:`_expression.lateral` function.
.. seealso::
:ref:`tutorial_lateral_correlation` - overview of usage.
"""
return Lateral._construct(self, name=name)
@util.deprecated(
"1.4",
message="The :meth:`.Selectable.replace_selectable` method is "
"deprecated, and will be removed in a future release. Similar "
"functionality is available via the sqlalchemy.sql.visitors module.",
)
@util.preload_module("sqlalchemy.sql.util")
def replace_selectable(self, old: FromClause, alias: Alias) -> Self:
"""Replace all occurrences of :class:`_expression.FromClause`
'old' with the given :class:`_expression.Alias`
object, returning a copy of this :class:`_expression.FromClause`.
"""
return util.preloaded.sql_util.ClauseAdapter(alias).traverse(self)
def corresponding_column(
self, column: KeyedColumnElement[Any], require_embedded: bool = False
) -> Optional[KeyedColumnElement[Any]]:
"""Given a :class:`_expression.ColumnElement`, return the exported
:class:`_expression.ColumnElement` object from the
:attr:`_expression.Selectable.exported_columns`
collection of this :class:`_expression.Selectable`
which corresponds to that
original :class:`_expression.ColumnElement` via a common ancestor
column.
:param column: the target :class:`_expression.ColumnElement`
to be matched.
:param require_embedded: only return corresponding columns for
the given :class:`_expression.ColumnElement`, if the given
:class:`_expression.ColumnElement`
is actually present within a sub-element
of this :class:`_expression.Selectable`.
Normally the column will match if
it merely shares a common ancestor with one of the exported
columns of this :class:`_expression.Selectable`.
.. seealso::
:attr:`_expression.Selectable.exported_columns` - the
:class:`_expression.ColumnCollection`
that is used for the operation.
:meth:`_expression.ColumnCollection.corresponding_column`
- implementation
method.
"""
return self.exported_columns.corresponding_column(
column, require_embedded
)
class HasPrefixes:
_prefixes: Tuple[Tuple[DQLDMLClauseElement, str], ...] = ()
_has_prefixes_traverse_internals: _TraverseInternalsType = [
("_prefixes", InternalTraversal.dp_prefix_sequence)
]
@_generative
@_document_text_coercion(
"prefixes",
":meth:`_expression.HasPrefixes.prefix_with`",
":paramref:`.HasPrefixes.prefix_with.*prefixes`",
)
def prefix_with(
self,
*prefixes: _TextCoercedExpressionArgument[Any],
dialect: str = "*",
) -> Self:
r"""Add one or more expressions following the statement keyword, i.e.
SELECT, INSERT, UPDATE, or DELETE. Generative.
This is used to support backend-specific prefix keywords such as those
provided by MySQL.
E.g.::
stmt = table.insert().prefix_with("LOW_PRIORITY", dialect="mysql")
# MySQL 5.7 optimizer hints
stmt = select(table).prefix_with(
"/*+ BKA(t1) */", dialect="mysql")
Multiple prefixes can be specified by multiple calls
to :meth:`_expression.HasPrefixes.prefix_with`.
:param \*prefixes: textual or :class:`_expression.ClauseElement`
construct which
will be rendered following the INSERT, UPDATE, or DELETE
keyword.
:param dialect: optional string dialect name which will
limit rendering of this prefix to only that dialect.
"""
self._prefixes = self._prefixes + tuple(
[
(coercions.expect(roles.StatementOptionRole, p), dialect)
for p in prefixes
]
)
return self
class HasSuffixes:
_suffixes: Tuple[Tuple[DQLDMLClauseElement, str], ...] = ()
_has_suffixes_traverse_internals: _TraverseInternalsType = [
("_suffixes", InternalTraversal.dp_prefix_sequence)
]
@_generative
@_document_text_coercion(
"suffixes",
":meth:`_expression.HasSuffixes.suffix_with`",
":paramref:`.HasSuffixes.suffix_with.*suffixes`",
)
def suffix_with(
self,
*suffixes: _TextCoercedExpressionArgument[Any],
dialect: str = "*",
) -> Self:
r"""Add one or more expressions following the statement as a whole.
This is used to support backend-specific suffix keywords on
certain constructs.
E.g.::
stmt = select(col1, col2).cte().suffix_with(
"cycle empno set y_cycle to 1 default 0", dialect="oracle")
Multiple suffixes can be specified by multiple calls
to :meth:`_expression.HasSuffixes.suffix_with`.
:param \*suffixes: textual or :class:`_expression.ClauseElement`
construct which
will be rendered following the target clause.
:param dialect: Optional string dialect name which will
limit rendering of this suffix to only that dialect.
"""
self._suffixes = self._suffixes + tuple(
[
(coercions.expect(roles.StatementOptionRole, p), dialect)
for p in suffixes
]
)
return self
class HasHints:
_hints: util.immutabledict[Tuple[FromClause, str], str] = (
util.immutabledict()
)
_statement_hints: Tuple[Tuple[str, str], ...] = ()
_has_hints_traverse_internals: _TraverseInternalsType = [
("_statement_hints", InternalTraversal.dp_statement_hint_list),
("_hints", InternalTraversal.dp_table_hint_list),
]
def with_statement_hint(self, text: str, dialect_name: str = "*") -> Self:
"""Add a statement hint to this :class:`_expression.Select` or
other selectable object.
This method is similar to :meth:`_expression.Select.with_hint`
except that
it does not require an individual table, and instead applies to the
statement as a whole.
Hints here are specific to the backend database and may include
directives such as isolation levels, file directives, fetch directives,
etc.
.. seealso::
:meth:`_expression.Select.with_hint`
:meth:`_expression.Select.prefix_with` - generic SELECT prefixing
which also can suit some database-specific HINT syntaxes such as
MySQL optimizer hints
"""
return self._with_hint(None, text, dialect_name)
@_generative
def with_hint(
self,
selectable: _FromClauseArgument,
text: str,
dialect_name: str = "*",
) -> Self:
r"""Add an indexing or other executional context hint for the given
selectable to this :class:`_expression.Select` or other selectable
object.
The text of the hint is rendered in the appropriate
location for the database backend in use, relative
to the given :class:`_schema.Table` or :class:`_expression.Alias`
passed as the
``selectable`` argument. The dialect implementation
typically uses Python string substitution syntax
with the token ``%(name)s`` to render the name of
the table or alias. E.g. when using Oracle, the
following::
select(mytable).\
with_hint(mytable, "index(%(name)s ix_mytable)")
Would render SQL as::
select /*+ index(mytable ix_mytable) */ ... from mytable
The ``dialect_name`` option will limit the rendering of a particular
hint to a particular backend. Such as, to add hints for both Oracle
and Sybase simultaneously::
select(mytable).\
with_hint(mytable, "index(%(name)s ix_mytable)", 'oracle').\
with_hint(mytable, "WITH INDEX ix_mytable", 'mssql')
.. seealso::
:meth:`_expression.Select.with_statement_hint`
"""
return self._with_hint(selectable, text, dialect_name)
def _with_hint(
self,
selectable: Optional[_FromClauseArgument],
text: str,
dialect_name: str,
) -> Self:
if selectable is None:
self._statement_hints += ((dialect_name, text),)
else:
self._hints = self._hints.union(
{
(
coercions.expect(roles.FromClauseRole, selectable),
dialect_name,
): text
}
)
return self
class FromClause(roles.AnonymizedFromClauseRole, Selectable):
"""Represent an element that can be used within the ``FROM``
clause of a ``SELECT`` statement.
The most common forms of :class:`_expression.FromClause` are the
:class:`_schema.Table` and the :func:`_expression.select` constructs. Key
features common to all :class:`_expression.FromClause` objects include:
* a :attr:`.c` collection, which provides per-name access to a collection
of :class:`_expression.ColumnElement` objects.
* a :attr:`.primary_key` attribute, which is a collection of all those
:class:`_expression.ColumnElement`
objects that indicate the ``primary_key`` flag.
* Methods to generate various derivations of a "from" clause, including
:meth:`_expression.FromClause.alias`,
:meth:`_expression.FromClause.join`,
:meth:`_expression.FromClause.select`.
"""
__visit_name__ = "fromclause"
named_with_column = False
@util.ro_non_memoized_property
def _hide_froms(self) -> Iterable[FromClause]:
return ()
_is_clone_of: Optional[FromClause]
_columns: ColumnCollection[Any, Any]
schema: Optional[str] = None
"""Define the 'schema' attribute for this :class:`_expression.FromClause`.
This is typically ``None`` for most objects except that of
:class:`_schema.Table`, where it is taken as the value of the
:paramref:`_schema.Table.schema` argument.
"""
is_selectable = True
_is_from_clause = True
_is_join = False
_use_schema_map = False
def select(self) -> Select[Any]:
r"""Return a SELECT of this :class:`_expression.FromClause`.
e.g.::
stmt = some_table.select().where(some_table.c.id == 5)
.. seealso::
:func:`_expression.select` - general purpose
method which allows for arbitrary column lists.
"""
return Select(self)
def join(
self,
right: _FromClauseArgument,
onclause: Optional[_ColumnExpressionArgument[bool]] = None,
isouter: bool = False,
full: bool = False,
) -> Join:
"""Return a :class:`_expression.Join` from this
:class:`_expression.FromClause`
to another :class:`FromClause`.
E.g.::
from sqlalchemy import join
j = user_table.join(address_table,
user_table.c.id == address_table.c.user_id)
stmt = select(user_table).select_from(j)
would emit SQL along the lines of::
SELECT user.id, user.name FROM user
JOIN address ON user.id = address.user_id
:param right: the right side of the join; this is any
:class:`_expression.FromClause` object such as a
:class:`_schema.Table` object, and
may also be a selectable-compatible object such as an ORM-mapped
class.
:param onclause: a SQL expression representing the ON clause of the
join. If left at ``None``, :meth:`_expression.FromClause.join`
will attempt to
join the two tables based on a foreign key relationship.
:param isouter: if True, render a LEFT OUTER JOIN, instead of JOIN.
:param full: if True, render a FULL OUTER JOIN, instead of LEFT OUTER
JOIN. Implies :paramref:`.FromClause.join.isouter`.
.. seealso::
:func:`_expression.join` - standalone function
:class:`_expression.Join` - the type of object produced
"""
return Join(self, right, onclause, isouter, full)
def outerjoin(
self,
right: _FromClauseArgument,
onclause: Optional[_ColumnExpressionArgument[bool]] = None,
full: bool = False,
) -> Join:
"""Return a :class:`_expression.Join` from this
:class:`_expression.FromClause`
to another :class:`FromClause`, with the "isouter" flag set to
True.
E.g.::
from sqlalchemy import outerjoin
j = user_table.outerjoin(address_table,
user_table.c.id == address_table.c.user_id)
The above is equivalent to::
j = user_table.join(
address_table,
user_table.c.id == address_table.c.user_id,
isouter=True)
:param right: the right side of the join; this is any
:class:`_expression.FromClause` object such as a
:class:`_schema.Table` object, and
may also be a selectable-compatible object such as an ORM-mapped
class.
:param onclause: a SQL expression representing the ON clause of the
join. If left at ``None``, :meth:`_expression.FromClause.join`
will attempt to
join the two tables based on a foreign key relationship.
:param full: if True, render a FULL OUTER JOIN, instead of
LEFT OUTER JOIN.
.. seealso::
:meth:`_expression.FromClause.join`
:class:`_expression.Join`
"""
return Join(self, right, onclause, True, full)
def alias(
self, name: Optional[str] = None, flat: bool = False
) -> NamedFromClause:
"""Return an alias of this :class:`_expression.FromClause`.
E.g.::
a2 = some_table.alias('a2')
The above code creates an :class:`_expression.Alias`
object which can be used
as a FROM clause in any SELECT statement.
.. seealso::
:ref:`tutorial_using_aliases`
:func:`_expression.alias`
"""
return Alias._construct(self, name=name)
def tablesample(
self,
sampling: Union[float, Function[Any]],
name: Optional[str] = None,
seed: Optional[roles.ExpressionElementRole[Any]] = None,
) -> TableSample:
"""Return a TABLESAMPLE alias of this :class:`_expression.FromClause`.
The return value is the :class:`_expression.TableSample`
construct also
provided by the top-level :func:`_expression.tablesample` function.
.. seealso::
:func:`_expression.tablesample` - usage guidelines and parameters
"""
return TableSample._construct(
self, sampling=sampling, name=name, seed=seed
)
def is_derived_from(self, fromclause: Optional[FromClause]) -> bool:
"""Return ``True`` if this :class:`_expression.FromClause` is
'derived' from the given ``FromClause``.
An example would be an Alias of a Table is derived from that Table.
"""
# this is essentially an "identity" check in the base class.
# Other constructs override this to traverse through
# contained elements.
return fromclause in self._cloned_set
def _is_lexical_equivalent(self, other: FromClause) -> bool:
"""Return ``True`` if this :class:`_expression.FromClause` and
the other represent the same lexical identity.
This tests if either one is a copy of the other, or
if they are the same via annotation identity.
"""
return bool(self._cloned_set.intersection(other._cloned_set))
@util.ro_non_memoized_property
def description(self) -> str:
"""A brief description of this :class:`_expression.FromClause`.
Used primarily for error message formatting.
"""
return getattr(self, "name", self.__class__.__name__ + " object")
def _generate_fromclause_column_proxies(
self, fromclause: FromClause
) -> None:
fromclause._columns._populate_separate_keys(
col._make_proxy(fromclause) for col in self.c
)
@util.ro_non_memoized_property
def exported_columns(
self,
) -> ReadOnlyColumnCollection[str, KeyedColumnElement[Any]]:
"""A :class:`_expression.ColumnCollection`
that represents the "exported"
columns of this :class:`_expression.Selectable`.
The "exported" columns for a :class:`_expression.FromClause`
object are synonymous
with the :attr:`_expression.FromClause.columns` collection.
.. versionadded:: 1.4
.. seealso::
:attr:`_expression.Selectable.exported_columns`
:attr:`_expression.SelectBase.exported_columns`
"""
return self.c
@util.ro_non_memoized_property
def columns(
self,
) -> ReadOnlyColumnCollection[str, KeyedColumnElement[Any]]:
"""A named-based collection of :class:`_expression.ColumnElement`
objects maintained by this :class:`_expression.FromClause`.
The :attr:`.columns`, or :attr:`.c` collection, is the gateway
to the construction of SQL expressions using table-bound or
other selectable-bound columns::
select(mytable).where(mytable.c.somecolumn == 5)
:return: a :class:`.ColumnCollection` object.
"""
return self.c
@util.ro_memoized_property
def c(self) -> ReadOnlyColumnCollection[str, KeyedColumnElement[Any]]:
"""
A synonym for :attr:`.FromClause.columns`
:return: a :class:`.ColumnCollection`
"""
if "_columns" not in self.__dict__:
self._init_collections()
self._populate_column_collection()
return self._columns.as_readonly()
@util.ro_non_memoized_property
def entity_namespace(self) -> _EntityNamespace:
"""Return a namespace used for name-based access in SQL expressions.
This is the namespace that is used to resolve "filter_by()" type
expressions, such as::
stmt.filter_by(address='some address')
It defaults to the ``.c`` collection, however internally it can
be overridden using the "entity_namespace" annotation to deliver
alternative results.
"""
return self.c
@util.ro_memoized_property
def primary_key(self) -> Iterable[NamedColumn[Any]]:
"""Return the iterable collection of :class:`_schema.Column` objects
which comprise the primary key of this :class:`_selectable.FromClause`.
For a :class:`_schema.Table` object, this collection is represented
by the :class:`_schema.PrimaryKeyConstraint` which itself is an
iterable collection of :class:`_schema.Column` objects.
"""
self._init_collections()
self._populate_column_collection()
return self.primary_key
@util.ro_memoized_property
def foreign_keys(self) -> Iterable[ForeignKey]:
"""Return the collection of :class:`_schema.ForeignKey` marker objects
which this FromClause references.
Each :class:`_schema.ForeignKey` is a member of a
:class:`_schema.Table`-wide
:class:`_schema.ForeignKeyConstraint`.
.. seealso::
:attr:`_schema.Table.foreign_key_constraints`
"""
self._init_collections()
self._populate_column_collection()
return self.foreign_keys
def _reset_column_collection(self) -> None:
"""Reset the attributes linked to the ``FromClause.c`` attribute.
This collection is separate from all the other memoized things
as it has shown to be sensitive to being cleared out in situations
where enclosing code, typically in a replacement traversal scenario,
has already established strong relationships
with the exported columns.
The collection is cleared for the case where a table is having a
column added to it as well as within a Join during copy internals.
"""
for key in ["_columns", "columns", "c", "primary_key", "foreign_keys"]:
self.__dict__.pop(key, None)
@util.ro_non_memoized_property
def _select_iterable(self) -> _SelectIterable:
return (c for c in self.c if not _never_select_column(c))
def _init_collections(self) -> None:
assert "_columns" not in self.__dict__
assert "primary_key" not in self.__dict__
assert "foreign_keys" not in self.__dict__
self._columns = ColumnCollection()
self.primary_key = ColumnSet() # type: ignore
self.foreign_keys = set() # type: ignore
@property
def _cols_populated(self) -> bool:
return "_columns" in self.__dict__
def _populate_column_collection(self) -> None:
"""Called on subclasses to establish the .c collection.
Each implementation has a different way of establishing
this collection.
"""
def _refresh_for_new_column(self, column: ColumnElement[Any]) -> None:
"""Given a column added to the .c collection of an underlying
selectable, produce the local version of that column, assuming this
selectable ultimately should proxy this column.
this is used to "ping" a derived selectable to add a new column
to its .c. collection when a Column has been added to one of the
Table objects it ultimately derives from.
If the given selectable hasn't populated its .c. collection yet,
it should at least pass on the message to the contained selectables,
but it will return None.
This method is currently used by Declarative to allow Table
columns to be added to a partially constructed inheritance
mapping that may have already produced joins. The method
isn't public right now, as the full span of implications
and/or caveats aren't yet clear.
It's also possible that this functionality could be invoked by
default via an event, which would require that
selectables maintain a weak referencing collection of all
derivations.
"""
self._reset_column_collection()
def _anonymous_fromclause(
self, *, name: Optional[str] = None, flat: bool = False
) -> FromClause:
return self.alias(name=name)
if TYPE_CHECKING:
def self_group(
self, against: Optional[OperatorType] = None
) -> Union[FromGrouping, Self]: ...
class NamedFromClause(FromClause):
"""A :class:`.FromClause` that has a name.
Examples include tables, subqueries, CTEs, aliased tables.
.. versionadded:: 2.0
"""
named_with_column = True
name: str
@util.preload_module("sqlalchemy.sql.sqltypes")
def table_valued(self) -> TableValuedColumn[Any]:
"""Return a :class:`_sql.TableValuedColumn` object for this
:class:`_expression.FromClause`.
A :class:`_sql.TableValuedColumn` is a :class:`_sql.ColumnElement` that
represents a complete row in a table. Support for this construct is
backend dependent, and is supported in various forms by backends
such as PostgreSQL, Oracle and SQL Server.
E.g.:
.. sourcecode:: pycon+sql
>>> from sqlalchemy import select, column, func, table
>>> a = table("a", column("id"), column("x"), column("y"))
>>> stmt = select(func.row_to_json(a.table_valued()))
>>> print(stmt)
{printsql}SELECT row_to_json(a) AS row_to_json_1
FROM a
.. versionadded:: 1.4.0b2
.. seealso::
:ref:`tutorial_functions` - in the :ref:`unified_tutorial`
"""
return TableValuedColumn(self, type_api.TABLEVALUE)
class SelectLabelStyle(Enum):
"""Label style constants that may be passed to
:meth:`_sql.Select.set_label_style`."""
LABEL_STYLE_NONE = 0
"""Label style indicating no automatic labeling should be applied to the
columns clause of a SELECT statement.
Below, the columns named ``columna`` are both rendered as is, meaning that
the name ``columna`` can only refer to the first occurrence of this name
within a result set, as well as if the statement were used as a subquery:
.. sourcecode:: pycon+sql
>>> from sqlalchemy import table, column, select, true, LABEL_STYLE_NONE
>>> table1 = table("table1", column("columna"), column("columnb"))
>>> table2 = table("table2", column("columna"), column("columnc"))
>>> print(select(table1, table2).join(table2, true()).set_label_style(LABEL_STYLE_NONE))
{printsql}SELECT table1.columna, table1.columnb, table2.columna, table2.columnc
FROM table1 JOIN table2 ON true
Used with the :meth:`_sql.Select.set_label_style` method.
.. versionadded:: 1.4
""" # noqa: E501
LABEL_STYLE_TABLENAME_PLUS_COL = 1
"""Label style indicating all columns should be labeled as
``<tablename>_<columnname>`` when generating the columns clause of a SELECT
statement, to disambiguate same-named columns referenced from different
tables, aliases, or subqueries.
Below, all column names are given a label so that the two same-named
columns ``columna`` are disambiguated as ``table1_columna`` and
``table2_columna``:
.. sourcecode:: pycon+sql
>>> from sqlalchemy import table, column, select, true, LABEL_STYLE_TABLENAME_PLUS_COL
>>> table1 = table("table1", column("columna"), column("columnb"))
>>> table2 = table("table2", column("columna"), column("columnc"))
>>> print(select(table1, table2).join(table2, true()).set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL))
{printsql}SELECT table1.columna AS table1_columna, table1.columnb AS table1_columnb, table2.columna AS table2_columna, table2.columnc AS table2_columnc
FROM table1 JOIN table2 ON true
Used with the :meth:`_sql.GenerativeSelect.set_label_style` method.
Equivalent to the legacy method ``Select.apply_labels()``;
:data:`_sql.LABEL_STYLE_TABLENAME_PLUS_COL` is SQLAlchemy's legacy
auto-labeling style. :data:`_sql.LABEL_STYLE_DISAMBIGUATE_ONLY` provides a
less intrusive approach to disambiguation of same-named column expressions.
.. versionadded:: 1.4
""" # noqa: E501
LABEL_STYLE_DISAMBIGUATE_ONLY = 2
"""Label style indicating that columns with a name that conflicts with
an existing name should be labeled with a semi-anonymizing label
when generating the columns clause of a SELECT statement.
Below, most column names are left unaffected, except for the second
occurrence of the name ``columna``, which is labeled using the
label ``columna_1`` to disambiguate it from that of ``tablea.columna``:
.. sourcecode:: pycon+sql
>>> from sqlalchemy import table, column, select, true, LABEL_STYLE_DISAMBIGUATE_ONLY
>>> table1 = table("table1", column("columna"), column("columnb"))
>>> table2 = table("table2", column("columna"), column("columnc"))
>>> print(select(table1, table2).join(table2, true()).set_label_style(LABEL_STYLE_DISAMBIGUATE_ONLY))
{printsql}SELECT table1.columna, table1.columnb, table2.columna AS columna_1, table2.columnc
FROM table1 JOIN table2 ON true
Used with the :meth:`_sql.GenerativeSelect.set_label_style` method,
:data:`_sql.LABEL_STYLE_DISAMBIGUATE_ONLY` is the default labeling style
for all SELECT statements outside of :term:`1.x style` ORM queries.
.. versionadded:: 1.4
""" # noqa: E501
LABEL_STYLE_DEFAULT = LABEL_STYLE_DISAMBIGUATE_ONLY
"""The default label style, refers to
:data:`_sql.LABEL_STYLE_DISAMBIGUATE_ONLY`.
.. versionadded:: 1.4
"""
LABEL_STYLE_LEGACY_ORM = 3
(
LABEL_STYLE_NONE,
LABEL_STYLE_TABLENAME_PLUS_COL,
LABEL_STYLE_DISAMBIGUATE_ONLY,
_,
) = list(SelectLabelStyle)
LABEL_STYLE_DEFAULT = LABEL_STYLE_DISAMBIGUATE_ONLY
class Join(roles.DMLTableRole, FromClause):
"""Represent a ``JOIN`` construct between two
:class:`_expression.FromClause`
elements.
The public constructor function for :class:`_expression.Join`
is the module-level
:func:`_expression.join()` function, as well as the
:meth:`_expression.FromClause.join` method
of any :class:`_expression.FromClause` (e.g. such as
:class:`_schema.Table`).
.. seealso::
:func:`_expression.join`
:meth:`_expression.FromClause.join`
"""
__visit_name__ = "join"
_traverse_internals: _TraverseInternalsType = [
("left", InternalTraversal.dp_clauseelement),
("right", InternalTraversal.dp_clauseelement),
("onclause", InternalTraversal.dp_clauseelement),
("isouter", InternalTraversal.dp_boolean),
("full", InternalTraversal.dp_boolean),
]
_is_join = True
left: FromClause
right: FromClause
onclause: Optional[ColumnElement[bool]]
isouter: bool
full: bool
def __init__(
self,
left: _FromClauseArgument,
right: _FromClauseArgument,
onclause: Optional[_OnClauseArgument] = None,
isouter: bool = False,
full: bool = False,
):
"""Construct a new :class:`_expression.Join`.
The usual entrypoint here is the :func:`_expression.join`
function or the :meth:`_expression.FromClause.join` method of any
:class:`_expression.FromClause` object.
"""
# when deannotate was removed here, callcounts went up for ORM
# compilation of eager joins, since there were more comparisons of
# annotated objects. test_orm.py -> test_fetch_results
# was therefore changed to show a more real-world use case, where the
# compilation is cached; there's no change in post-cache callcounts.
# callcounts for a single compilation in that particular test
# that includes about eight joins about 1100 extra fn calls, from
# 29200 -> 30373
self.left = coercions.expect(
roles.FromClauseRole,
left,
)
self.right = coercions.expect(
roles.FromClauseRole,
right,
).self_group()
if onclause is None:
self.onclause = self._match_primaries(self.left, self.right)
else:
# note: taken from If91f61527236fd4d7ae3cad1f24c38be921c90ba
# not merged yet
self.onclause = coercions.expect(
roles.OnClauseRole, onclause
).self_group(against=operators._asbool)
self.isouter = isouter
self.full = full
@util.ro_non_memoized_property
def description(self) -> str:
return "Join object on %s(%d) and %s(%d)" % (
self.left.description,
id(self.left),
self.right.description,
id(self.right),
)
def is_derived_from(self, fromclause: Optional[FromClause]) -> bool:
return (
# use hash() to ensure direct comparison to annotated works
# as well
hash(fromclause) == hash(self)
or self.left.is_derived_from(fromclause)
or self.right.is_derived_from(fromclause)
)
def self_group(
self, against: Optional[OperatorType] = None
) -> FromGrouping:
return FromGrouping(self)
@util.preload_module("sqlalchemy.sql.util")
def _populate_column_collection(self) -> None:
sqlutil = util.preloaded.sql_util
columns: List[KeyedColumnElement[Any]] = [c for c in self.left.c] + [
c for c in self.right.c
]
self.primary_key.extend( # type: ignore
sqlutil.reduce_columns(
(c for c in columns if c.primary_key), self.onclause
)
)
self._columns._populate_separate_keys(
(col._tq_key_label, col) for col in columns
)
self.foreign_keys.update( # type: ignore
itertools.chain(*[col.foreign_keys for col in columns])
)
def _copy_internals(
self, clone: _CloneCallableType = _clone, **kw: Any
) -> None:
# see Select._copy_internals() for similar concept
# here we pre-clone "left" and "right" so that we can
# determine the new FROM clauses
all_the_froms = set(
itertools.chain(
_from_objects(self.left),
_from_objects(self.right),
)
)
# run the clone on those. these will be placed in the
# cache used by the clone function
new_froms = {f: clone(f, **kw) for f in all_the_froms}
# set up a special replace function that will replace for
# ColumnClause with parent table referring to those
# replaced FromClause objects
def replace(
obj: Union[BinaryExpression[Any], ColumnClause[Any]],
**kw: Any,
) -> Optional[KeyedColumnElement[ColumnElement[Any]]]:
if isinstance(obj, ColumnClause) and obj.table in new_froms:
newelem = new_froms[obj.table].corresponding_column(obj)
return newelem
return None
kw["replace"] = replace
# run normal _copy_internals. the clones for
# left and right will come from the clone function's
# cache
super()._copy_internals(clone=clone, **kw)
self._reset_memoizations()
def _refresh_for_new_column(self, column: ColumnElement[Any]) -> None:
super()._refresh_for_new_column(column)
self.left._refresh_for_new_column(column)
self.right._refresh_for_new_column(column)
def _match_primaries(
self,
left: FromClause,
right: FromClause,
) -> ColumnElement[bool]:
if isinstance(left, Join):
left_right = left.right
else:
left_right = None
return self._join_condition(left, right, a_subset=left_right)
@classmethod
def _join_condition(
cls,
a: FromClause,
b: FromClause,
*,
a_subset: Optional[FromClause] = None,
consider_as_foreign_keys: Optional[
AbstractSet[ColumnClause[Any]]
] = None,
) -> ColumnElement[bool]:
"""Create a join condition between two tables or selectables.
See sqlalchemy.sql.util.join_condition() for full docs.
"""
constraints = cls._joincond_scan_left_right(
a, a_subset, b, consider_as_foreign_keys
)
if len(constraints) > 1:
cls._joincond_trim_constraints(
a, b, constraints, consider_as_foreign_keys
)
if len(constraints) == 0:
if isinstance(b, FromGrouping):
hint = (
" Perhaps you meant to convert the right side to a "
"subquery using alias()?"
)
else:
hint = ""
raise exc.NoForeignKeysError(
"Can't find any foreign key relationships "
"between '%s' and '%s'.%s"
% (a.description, b.description, hint)
)
crit = [(x == y) for x, y in list(constraints.values())[0]]
if len(crit) == 1:
return crit[0]
else:
return and_(*crit)
@classmethod
def _can_join(
cls,
left: FromClause,
right: FromClause,
*,
consider_as_foreign_keys: Optional[
AbstractSet[ColumnClause[Any]]
] = None,
) -> bool:
if isinstance(left, Join):
left_right = left.right
else:
left_right = None
constraints = cls._joincond_scan_left_right(
a=left,
b=right,
a_subset=left_right,
consider_as_foreign_keys=consider_as_foreign_keys,
)
return bool(constraints)
@classmethod
@util.preload_module("sqlalchemy.sql.util")
def _joincond_scan_left_right(
cls,
a: FromClause,
a_subset: Optional[FromClause],
b: FromClause,
consider_as_foreign_keys: Optional[AbstractSet[ColumnClause[Any]]],
) -> collections.defaultdict[
Optional[ForeignKeyConstraint],
List[Tuple[ColumnClause[Any], ColumnClause[Any]]],
]:
sql_util = util.preloaded.sql_util
a = coercions.expect(roles.FromClauseRole, a)
b = coercions.expect(roles.FromClauseRole, b)
constraints: collections.defaultdict[
Optional[ForeignKeyConstraint],
List[Tuple[ColumnClause[Any], ColumnClause[Any]]],
] = collections.defaultdict(list)
for left in (a_subset, a):
if left is None:
continue
for fk in sorted(
b.foreign_keys,
key=lambda fk: fk.parent._creation_order,
):
if (
consider_as_foreign_keys is not None
and fk.parent not in consider_as_foreign_keys
):
continue
try:
col = fk.get_referent(left)
except exc.NoReferenceError as nrte:
table_names = {t.name for t in sql_util.find_tables(left)}
if nrte.table_name in table_names:
raise
else:
continue
if col is not None:
constraints[fk.constraint].append((col, fk.parent))
if left is not b:
for fk in sorted(
left.foreign_keys,
key=lambda fk: fk.parent._creation_order,
):
if (
consider_as_foreign_keys is not None
and fk.parent not in consider_as_foreign_keys
):
continue
try:
col = fk.get_referent(b)
except exc.NoReferenceError as nrte:
table_names = {t.name for t in sql_util.find_tables(b)}
if nrte.table_name in table_names:
raise
else:
continue
if col is not None:
constraints[fk.constraint].append((col, fk.parent))
if constraints:
break
return constraints
@classmethod
def _joincond_trim_constraints(
cls,
a: FromClause,
b: FromClause,
constraints: Dict[Any, Any],
consider_as_foreign_keys: Optional[Any],
) -> None:
# more than one constraint matched. narrow down the list
# to include just those FKCs that match exactly to
# "consider_as_foreign_keys".
if consider_as_foreign_keys:
for const in list(constraints):
if {f.parent for f in const.elements} != set(
consider_as_foreign_keys
):
del constraints[const]
# if still multiple constraints, but
# they all refer to the exact same end result, use it.
if len(constraints) > 1:
dedupe = {tuple(crit) for crit in constraints.values()}
if len(dedupe) == 1:
key = list(constraints)[0]
constraints = {key: constraints[key]}
if len(constraints) != 1:
raise exc.AmbiguousForeignKeysError(
"Can't determine join between '%s' and '%s'; "
"tables have more than one foreign key "
"constraint relationship between them. "
"Please specify the 'onclause' of this "
"join explicitly." % (a.description, b.description)
)
def select(self) -> Select[Any]:
r"""Create a :class:`_expression.Select` from this
:class:`_expression.Join`.
E.g.::
stmt = table_a.join(table_b, table_a.c.id == table_b.c.a_id)
stmt = stmt.select()
The above will produce a SQL string resembling::
SELECT table_a.id, table_a.col, table_b.id, table_b.a_id
FROM table_a JOIN table_b ON table_a.id = table_b.a_id
"""
return Select(self.left, self.right).select_from(self)
@util.preload_module("sqlalchemy.sql.util")
def _anonymous_fromclause(
self, name: Optional[str] = None, flat: bool = False
) -> TODO_Any:
sqlutil = util.preloaded.sql_util
if flat:
if isinstance(self.left, (FromGrouping, Join)):
left_name = name # will recurse
else:
if name and isinstance(self.left, NamedFromClause):
left_name = f"{name}_{self.left.name}"
else:
left_name = name
if isinstance(self.right, (FromGrouping, Join)):
right_name = name # will recurse
else:
if name and isinstance(self.right, NamedFromClause):
right_name = f"{name}_{self.right.name}"
else:
right_name = name
left_a, right_a = (
self.left._anonymous_fromclause(name=left_name, flat=flat),
self.right._anonymous_fromclause(name=right_name, flat=flat),
)
adapter = sqlutil.ClauseAdapter(left_a).chain(
sqlutil.ClauseAdapter(right_a)
)
return left_a.join(
right_a,
adapter.traverse(self.onclause),
isouter=self.isouter,
full=self.full,
)
else:
return (
self.select()
.set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)
.correlate(None)
.alias(name)
)
@util.ro_non_memoized_property
def _hide_froms(self) -> Iterable[FromClause]:
return itertools.chain(
*[_from_objects(x.left, x.right) for x in self._cloned_set]
)
@util.ro_non_memoized_property
def _from_objects(self) -> List[FromClause]:
self_list: List[FromClause] = [self]
return self_list + self.left._from_objects + self.right._from_objects
class NoInit:
def __init__(self, *arg: Any, **kw: Any):
raise NotImplementedError(
"The %s class is not intended to be constructed "
"directly. Please use the %s() standalone "
"function or the %s() method available from appropriate "
"selectable objects."
% (
self.__class__.__name__,
self.__class__.__name__.lower(),
self.__class__.__name__.lower(),
)
)
class LateralFromClause(NamedFromClause):
"""mark a FROM clause as being able to render directly as LATERAL"""
# FromClause ->
# AliasedReturnsRows
# -> Alias only for FromClause
# -> Subquery only for SelectBase
# -> CTE only for HasCTE -> SelectBase, DML
# -> Lateral -> FromClause, but we accept SelectBase
# w/ non-deprecated coercion
# -> TableSample -> only for FromClause
class AliasedReturnsRows(NoInit, NamedFromClause):
"""Base class of aliases against tables, subqueries, and other
selectables."""
_is_from_container = True
_supports_derived_columns = False
element: ReturnsRows
_traverse_internals: _TraverseInternalsType = [
("element", InternalTraversal.dp_clauseelement),
("name", InternalTraversal.dp_anon_name),
]
@classmethod
def _construct(
cls,
selectable: Any,
*,
name: Optional[str] = None,
**kw: Any,
) -> Self:
obj = cls.__new__(cls)
obj._init(selectable, name=name, **kw)
return obj
def _init(self, selectable: Any, *, name: Optional[str] = None) -> None:
self.element = coercions.expect(
roles.ReturnsRowsRole, selectable, apply_propagate_attrs=self
)
self.element = selectable
self._orig_name = name
if name is None:
if (
isinstance(selectable, FromClause)
and selectable.named_with_column
):
name = getattr(selectable, "name", None)
if isinstance(name, _anonymous_label):
name = None
name = _anonymous_label.safe_construct(id(self), name or "anon")
self.name = name
def _refresh_for_new_column(self, column: ColumnElement[Any]) -> None:
super()._refresh_for_new_column(column)
self.element._refresh_for_new_column(column)
def _populate_column_collection(self) -> None:
self.element._generate_fromclause_column_proxies(self)
@util.ro_non_memoized_property
def description(self) -> str:
name = self.name
if isinstance(name, _anonymous_label):
name = "anon_1"
return name
@util.ro_non_memoized_property
def implicit_returning(self) -> bool:
return self.element.implicit_returning # type: ignore
@property
def original(self) -> ReturnsRows:
"""Legacy for dialects that are referring to Alias.original."""
return self.element
def is_derived_from(self, fromclause: Optional[FromClause]) -> bool:
if fromclause in self._cloned_set:
return True
return self.element.is_derived_from(fromclause)
def _copy_internals(
self, clone: _CloneCallableType = _clone, **kw: Any
) -> None:
existing_element = self.element
super()._copy_internals(clone=clone, **kw)
# the element clone is usually against a Table that returns the
# same object. don't reset exported .c. collections and other
# memoized details if it was not changed. this saves a lot on
# performance.
if existing_element is not self.element:
self._reset_column_collection()
@property
def _from_objects(self) -> List[FromClause]:
return [self]
class FromClauseAlias(AliasedReturnsRows):
element: FromClause
class Alias(roles.DMLTableRole, FromClauseAlias):
"""Represents an table or selectable alias (AS).
Represents an alias, as typically applied to any table or
sub-select within a SQL statement using the ``AS`` keyword (or
without the keyword on certain databases such as Oracle).
This object is constructed from the :func:`_expression.alias` module
level function as well as the :meth:`_expression.FromClause.alias`
method available
on all :class:`_expression.FromClause` subclasses.
.. seealso::
:meth:`_expression.FromClause.alias`
"""
__visit_name__ = "alias"
inherit_cache = True
element: FromClause
@classmethod
def _factory(
cls,
selectable: FromClause,
name: Optional[str] = None,
flat: bool = False,
) -> NamedFromClause:
return coercions.expect(
roles.FromClauseRole, selectable, allow_select=True
).alias(name=name, flat=flat)
class TableValuedAlias(LateralFromClause, Alias):
"""An alias against a "table valued" SQL function.
This construct provides for a SQL function that returns columns
to be used in the FROM clause of a SELECT statement. The
object is generated using the :meth:`_functions.FunctionElement.table_valued`
method, e.g.:
.. sourcecode:: pycon+sql
>>> from sqlalchemy import select, func
>>> fn = func.json_array_elements_text('["one", "two", "three"]').table_valued("value")
>>> print(select(fn.c.value))
{printsql}SELECT anon_1.value
FROM json_array_elements_text(:json_array_elements_text_1) AS anon_1
.. versionadded:: 1.4.0b2
.. seealso::
:ref:`tutorial_functions_table_valued` - in the :ref:`unified_tutorial`
""" # noqa: E501
__visit_name__ = "table_valued_alias"
_supports_derived_columns = True
_render_derived = False
_render_derived_w_types = False
joins_implicitly = False
_traverse_internals: _TraverseInternalsType = [
("element", InternalTraversal.dp_clauseelement),
("name", InternalTraversal.dp_anon_name),
("_tableval_type", InternalTraversal.dp_type),
("_render_derived", InternalTraversal.dp_boolean),
("_render_derived_w_types", InternalTraversal.dp_boolean),
]
def _init(
self,
selectable: Any,
*,
name: Optional[str] = None,
table_value_type: Optional[TableValueType] = None,
joins_implicitly: bool = False,
) -> None:
super()._init(selectable, name=name)
self.joins_implicitly = joins_implicitly
self._tableval_type = (
type_api.TABLEVALUE
if table_value_type is None
else table_value_type
)
@HasMemoized.memoized_attribute
def column(self) -> TableValuedColumn[Any]:
"""Return a column expression representing this
:class:`_sql.TableValuedAlias`.
This accessor is used to implement the
:meth:`_functions.FunctionElement.column_valued` method. See that
method for further details.
E.g.:
.. sourcecode:: pycon+sql
>>> print(select(func.some_func().table_valued("value").column))
{printsql}SELECT anon_1 FROM some_func() AS anon_1
.. seealso::
:meth:`_functions.FunctionElement.column_valued`
"""
return TableValuedColumn(self, self._tableval_type)
def alias(
self, name: Optional[str] = None, flat: bool = False
) -> TableValuedAlias:
"""Return a new alias of this :class:`_sql.TableValuedAlias`.
This creates a distinct FROM object that will be distinguished
from the original one when used in a SQL statement.
"""
tva: TableValuedAlias = TableValuedAlias._construct(
self,
name=name,
table_value_type=self._tableval_type,
joins_implicitly=self.joins_implicitly,
)
if self._render_derived:
tva._render_derived = True
tva._render_derived_w_types = self._render_derived_w_types
return tva
def lateral(self, name: Optional[str] = None) -> LateralFromClause:
"""Return a new :class:`_sql.TableValuedAlias` with the lateral flag
set, so that it renders as LATERAL.
.. seealso::
:func:`_expression.lateral`
"""
tva = self.alias(name=name)
tva._is_lateral = True
return tva
def render_derived(
self,
name: Optional[str] = None,
with_types: bool = False,
) -> TableValuedAlias:
"""Apply "render derived" to this :class:`_sql.TableValuedAlias`.
This has the effect of the individual column names listed out
after the alias name in the "AS" sequence, e.g.:
.. sourcecode:: pycon+sql
>>> print(
... select(
... func.unnest(array(["one", "two", "three"])).
table_valued("x", with_ordinality="o").render_derived()
... )
... )
{printsql}SELECT anon_1.x, anon_1.o
FROM unnest(ARRAY[%(param_1)s, %(param_2)s, %(param_3)s]) WITH ORDINALITY AS anon_1(x, o)
The ``with_types`` keyword will render column types inline within
the alias expression (this syntax currently applies to the
PostgreSQL database):
.. sourcecode:: pycon+sql
>>> print(
... select(
... func.json_to_recordset(
... '[{"a":1,"b":"foo"},{"a":"2","c":"bar"}]'
... )
... .table_valued(column("a", Integer), column("b", String))
... .render_derived(with_types=True)
... )
... )
{printsql}SELECT anon_1.a, anon_1.b FROM json_to_recordset(:json_to_recordset_1)
AS anon_1(a INTEGER, b VARCHAR)
:param name: optional string name that will be applied to the alias
generated. If left as None, a unique anonymizing name will be used.
:param with_types: if True, the derived columns will include the
datatype specification with each column. This is a special syntax
currently known to be required by PostgreSQL for some SQL functions.
""" # noqa: E501
# note: don't use the @_generative system here, keep a reference
# to the original object. otherwise you can have re-use of the
# python id() of the original which can cause name conflicts if
# a new anon-name grabs the same identifier as the local anon-name
# (just saw it happen on CI)
# construct against original to prevent memory growth
# for repeated generations
new_alias: TableValuedAlias = TableValuedAlias._construct(
self.element,
name=name,
table_value_type=self._tableval_type,
joins_implicitly=self.joins_implicitly,
)
new_alias._render_derived = True
new_alias._render_derived_w_types = with_types
return new_alias
class Lateral(FromClauseAlias, LateralFromClause):
"""Represent a LATERAL subquery.
This object is constructed from the :func:`_expression.lateral` module
level function as well as the :meth:`_expression.FromClause.lateral`
method available
on all :class:`_expression.FromClause` subclasses.
While LATERAL is part of the SQL standard, currently only more recent
PostgreSQL versions provide support for this keyword.
.. seealso::
:ref:`tutorial_lateral_correlation` - overview of usage.
"""
__visit_name__ = "lateral"
_is_lateral = True
inherit_cache = True
@classmethod
def _factory(
cls,
selectable: Union[SelectBase, _FromClauseArgument],
name: Optional[str] = None,
) -> LateralFromClause:
return coercions.expect(
roles.FromClauseRole, selectable, explicit_subquery=True
).lateral(name=name)
class TableSample(FromClauseAlias):
"""Represent a TABLESAMPLE clause.
This object is constructed from the :func:`_expression.tablesample` module
level function as well as the :meth:`_expression.FromClause.tablesample`
method
available on all :class:`_expression.FromClause` subclasses.
.. seealso::
:func:`_expression.tablesample`
"""
__visit_name__ = "tablesample"
_traverse_internals: _TraverseInternalsType = (
AliasedReturnsRows._traverse_internals
+ [
("sampling", InternalTraversal.dp_clauseelement),
("seed", InternalTraversal.dp_clauseelement),
]
)
@classmethod
def _factory(
cls,
selectable: _FromClauseArgument,
sampling: Union[float, Function[Any]],
name: Optional[str] = None,
seed: Optional[roles.ExpressionElementRole[Any]] = None,
) -> TableSample:
return coercions.expect(roles.FromClauseRole, selectable).tablesample(
sampling, name=name, seed=seed
)
@util.preload_module("sqlalchemy.sql.functions")
def _init( # type: ignore[override]
self,
selectable: Any,
*,
name: Optional[str] = None,
sampling: Union[float, Function[Any]],
seed: Optional[roles.ExpressionElementRole[Any]] = None,
) -> None:
assert sampling is not None
functions = util.preloaded.sql_functions
if not isinstance(sampling, functions.Function):
sampling = functions.func.system(sampling)
self.sampling: Function[Any] = sampling
self.seed = seed
super()._init(selectable, name=name)
def _get_method(self) -> Function[Any]:
return self.sampling
class CTE(
roles.DMLTableRole,
roles.IsCTERole,
Generative,
HasPrefixes,
HasSuffixes,
AliasedReturnsRows,
):
"""Represent a Common Table Expression.
The :class:`_expression.CTE` object is obtained using the
:meth:`_sql.SelectBase.cte` method from any SELECT statement. A less often
available syntax also allows use of the :meth:`_sql.HasCTE.cte` method
present on :term:`DML` constructs such as :class:`_sql.Insert`,
:class:`_sql.Update` and
:class:`_sql.Delete`. See the :meth:`_sql.HasCTE.cte` method for
usage details on CTEs.
.. seealso::
:ref:`tutorial_subqueries_ctes` - in the 2.0 tutorial
:meth:`_sql.HasCTE.cte` - examples of calling styles
"""
__visit_name__ = "cte"
_traverse_internals: _TraverseInternalsType = (
AliasedReturnsRows._traverse_internals
+ [
("_cte_alias", InternalTraversal.dp_clauseelement),
("_restates", InternalTraversal.dp_clauseelement),
("recursive", InternalTraversal.dp_boolean),
("nesting", InternalTraversal.dp_boolean),
]
+ HasPrefixes._has_prefixes_traverse_internals
+ HasSuffixes._has_suffixes_traverse_internals
)
element: HasCTE
@classmethod
def _factory(
cls,
selectable: HasCTE,
name: Optional[str] = None,
recursive: bool = False,
) -> CTE:
r"""Return a new :class:`_expression.CTE`,
or Common Table Expression instance.
Please see :meth:`_expression.HasCTE.cte` for detail on CTE usage.
"""
return coercions.expect(roles.HasCTERole, selectable).cte(
name=name, recursive=recursive
)
def _init(
self,
selectable: Select[Any],
*,
name: Optional[str] = None,
recursive: bool = False,
nesting: bool = False,
_cte_alias: Optional[CTE] = None,
_restates: Optional[CTE] = None,
_prefixes: Optional[Tuple[()]] = None,
_suffixes: Optional[Tuple[()]] = None,
) -> None:
self.recursive = recursive
self.nesting = nesting
self._cte_alias = _cte_alias
# Keep recursivity reference with union/union_all
self._restates = _restates
if _prefixes:
self._prefixes = _prefixes
if _suffixes:
self._suffixes = _suffixes
super()._init(selectable, name=name)
def _populate_column_collection(self) -> None:
if self._cte_alias is not None:
self._cte_alias._generate_fromclause_column_proxies(self)
else:
self.element._generate_fromclause_column_proxies(self)
def alias(self, name: Optional[str] = None, flat: bool = False) -> CTE:
"""Return an :class:`_expression.Alias` of this
:class:`_expression.CTE`.
This method is a CTE-specific specialization of the
:meth:`_expression.FromClause.alias` method.
.. seealso::
:ref:`tutorial_using_aliases`
:func:`_expression.alias`
"""
return CTE._construct(
self.element,
name=name,
recursive=self.recursive,
nesting=self.nesting,
_cte_alias=self,
_prefixes=self._prefixes,
_suffixes=self._suffixes,
)
def union(self, *other: _SelectStatementForCompoundArgument) -> CTE:
r"""Return a new :class:`_expression.CTE` with a SQL ``UNION``
of the original CTE against the given selectables provided
as positional arguments.
:param \*other: one or more elements with which to create a
UNION.
.. versionchanged:: 1.4.28 multiple elements are now accepted.
.. seealso::
:meth:`_sql.HasCTE.cte` - examples of calling styles
"""
assert is_select_statement(
self.element
), f"CTE element f{self.element} does not support union()"
return CTE._construct(
self.element.union(*other),
name=self.name,
recursive=self.recursive,
nesting=self.nesting,
_restates=self,
_prefixes=self._prefixes,
_suffixes=self._suffixes,
)
def union_all(self, *other: _SelectStatementForCompoundArgument) -> CTE:
r"""Return a new :class:`_expression.CTE` with a SQL ``UNION ALL``
of the original CTE against the given selectables provided
as positional arguments.
:param \*other: one or more elements with which to create a
UNION.
.. versionchanged:: 1.4.28 multiple elements are now accepted.
.. seealso::
:meth:`_sql.HasCTE.cte` - examples of calling styles
"""
assert is_select_statement(
self.element
), f"CTE element f{self.element} does not support union_all()"
return CTE._construct(
self.element.union_all(*other),
name=self.name,
recursive=self.recursive,
nesting=self.nesting,
_restates=self,
_prefixes=self._prefixes,
_suffixes=self._suffixes,
)
def _get_reference_cte(self) -> CTE:
"""
A recursive CTE is updated to attach the recursive part.
Updated CTEs should still refer to the original CTE.
This function returns this reference identifier.
"""
return self._restates if self._restates is not None else self
class _CTEOpts(NamedTuple):
nesting: bool
class _ColumnsPlusNames(NamedTuple):
required_label_name: Optional[str]
"""
string label name, if non-None, must be rendered as a
label, i.e. "AS <name>"
"""
proxy_key: Optional[str]
"""
proxy_key that is to be part of the result map for this
col. this is also the key in a fromclause.c or
select.selected_columns collection
"""
fallback_label_name: Optional[str]
"""
name that can be used to render an "AS <name>" when
we have to render a label even though
required_label_name was not given
"""
column: Union[ColumnElement[Any], TextClause]
"""
the ColumnElement itself
"""
repeated: bool
"""
True if this is a duplicate of a previous column
in the list of columns
"""
class SelectsRows(ReturnsRows):
"""Sub-base of ReturnsRows for elements that deliver rows
directly, namely SELECT and INSERT/UPDATE/DELETE..RETURNING"""
_label_style: SelectLabelStyle = LABEL_STYLE_NONE
def _generate_columns_plus_names(
self,
anon_for_dupe_key: bool,
cols: Optional[_SelectIterable] = None,
) -> List[_ColumnsPlusNames]:
"""Generate column names as rendered in a SELECT statement by
the compiler.
This is distinct from the _column_naming_convention generator that's
intended for population of .c collections and similar, which has
different rules. the collection returned here calls upon the
_column_naming_convention as well.
"""
if cols is None:
cols = self._all_selected_columns
key_naming_convention = SelectState._column_naming_convention(
self._label_style
)
names = {}
result: List[_ColumnsPlusNames] = []
result_append = result.append
table_qualified = self._label_style is LABEL_STYLE_TABLENAME_PLUS_COL
label_style_none = self._label_style is LABEL_STYLE_NONE
# a counter used for "dedupe" labels, which have double underscores
# in them and are never referred by name; they only act
# as positional placeholders. they need only be unique within
# the single columns clause they're rendered within (required by
# some dbs such as mysql). So their anon identity is tracked against
# a fixed counter rather than hash() identity.
dedupe_hash = 1
for c in cols:
repeated = False
if not c._render_label_in_columns_clause:
effective_name = required_label_name = fallback_label_name = (
None
)
elif label_style_none:
if TYPE_CHECKING:
assert is_column_element(c)
effective_name = required_label_name = None
fallback_label_name = c._non_anon_label or c._anon_name_label
else:
if TYPE_CHECKING:
assert is_column_element(c)
if table_qualified:
required_label_name = effective_name = (
fallback_label_name
) = c._tq_label
else:
effective_name = fallback_label_name = c._non_anon_label
required_label_name = None
if effective_name is None:
# it seems like this could be _proxy_key and we would
# not need _expression_label but it isn't
# giving us a clue when to use anon_label instead
expr_label = c._expression_label
if expr_label is None:
repeated = c._anon_name_label in names
names[c._anon_name_label] = c
effective_name = required_label_name = None
if repeated:
# here, "required_label_name" is sent as
# "None" and "fallback_label_name" is sent.
if table_qualified:
fallback_label_name = (
c._dedupe_anon_tq_label_idx(dedupe_hash)
)
dedupe_hash += 1
else:
fallback_label_name = c._dedupe_anon_label_idx(
dedupe_hash
)
dedupe_hash += 1
else:
fallback_label_name = c._anon_name_label
else:
required_label_name = effective_name = (
fallback_label_name
) = expr_label
if effective_name is not None:
if TYPE_CHECKING:
assert is_column_element(c)
if effective_name in names:
# when looking to see if names[name] is the same column as
# c, use hash(), so that an annotated version of the column
# is seen as the same as the non-annotated
if hash(names[effective_name]) != hash(c):
# different column under the same name. apply
# disambiguating label
if table_qualified:
required_label_name = fallback_label_name = (
c._anon_tq_label
)
else:
required_label_name = fallback_label_name = (
c._anon_name_label
)
if anon_for_dupe_key and required_label_name in names:
# here, c._anon_tq_label is definitely unique to
# that column identity (or annotated version), so
# this should always be true.
# this is also an infrequent codepath because
# you need two levels of duplication to be here
assert hash(names[required_label_name]) == hash(c)
# the column under the disambiguating label is
# already present. apply the "dedupe" label to
# subsequent occurrences of the column so that the
# original stays non-ambiguous
if table_qualified:
required_label_name = fallback_label_name = (
c._dedupe_anon_tq_label_idx(dedupe_hash)
)
dedupe_hash += 1
else:
required_label_name = fallback_label_name = (
c._dedupe_anon_label_idx(dedupe_hash)
)
dedupe_hash += 1
repeated = True
else:
names[required_label_name] = c
elif anon_for_dupe_key:
# same column under the same name. apply the "dedupe"
# label so that the original stays non-ambiguous
if table_qualified:
required_label_name = fallback_label_name = (
c._dedupe_anon_tq_label_idx(dedupe_hash)
)
dedupe_hash += 1
else:
required_label_name = fallback_label_name = (
c._dedupe_anon_label_idx(dedupe_hash)
)
dedupe_hash += 1
repeated = True
else:
names[effective_name] = c
result_append(
_ColumnsPlusNames(
required_label_name,
key_naming_convention(c),
fallback_label_name,
c,
repeated,
)
)
return result
class HasCTE(roles.HasCTERole, SelectsRows):
"""Mixin that declares a class to include CTE support."""
_has_ctes_traverse_internals: _TraverseInternalsType = [
("_independent_ctes", InternalTraversal.dp_clauseelement_list),
("_independent_ctes_opts", InternalTraversal.dp_plain_obj),
]
_independent_ctes: Tuple[CTE, ...] = ()
_independent_ctes_opts: Tuple[_CTEOpts, ...] = ()
@_generative
def add_cte(self, *ctes: CTE, nest_here: bool = False) -> Self:
r"""Add one or more :class:`_sql.CTE` constructs to this statement.
This method will associate the given :class:`_sql.CTE` constructs with
the parent statement such that they will each be unconditionally
rendered in the WITH clause of the final statement, even if not
referenced elsewhere within the statement or any sub-selects.
The optional :paramref:`.HasCTE.add_cte.nest_here` parameter when set
to True will have the effect that each given :class:`_sql.CTE` will
render in a WITH clause rendered directly along with this statement,
rather than being moved to the top of the ultimate rendered statement,
even if this statement is rendered as a subquery within a larger
statement.
This method has two general uses. One is to embed CTE statements that
serve some purpose without being referenced explicitly, such as the use
case of embedding a DML statement such as an INSERT or UPDATE as a CTE
inline with a primary statement that may draw from its results
indirectly. The other is to provide control over the exact placement
of a particular series of CTE constructs that should remain rendered
directly in terms of a particular statement that may be nested in a
larger statement.
E.g.::
from sqlalchemy import table, column, select
t = table('t', column('c1'), column('c2'))
ins = t.insert().values({"c1": "x", "c2": "y"}).cte()
stmt = select(t).add_cte(ins)
Would render::
WITH anon_1 AS
(INSERT INTO t (c1, c2) VALUES (:param_1, :param_2))
SELECT t.c1, t.c2
FROM t
Above, the "anon_1" CTE is not referenced in the SELECT
statement, however still accomplishes the task of running an INSERT
statement.
Similarly in a DML-related context, using the PostgreSQL
:class:`_postgresql.Insert` construct to generate an "upsert"::
from sqlalchemy import table, column
from sqlalchemy.dialects.postgresql import insert
t = table("t", column("c1"), column("c2"))
delete_statement_cte = (
t.delete().where(t.c.c1 < 1).cte("deletions")
)
insert_stmt = insert(t).values({"c1": 1, "c2": 2})
update_statement = insert_stmt.on_conflict_do_update(
index_elements=[t.c.c1],
set_={
"c1": insert_stmt.excluded.c1,
"c2": insert_stmt.excluded.c2,
},
).add_cte(delete_statement_cte)
print(update_statement)
The above statement renders as::
WITH deletions AS
(DELETE FROM t WHERE t.c1 < %(c1_1)s)
INSERT INTO t (c1, c2) VALUES (%(c1)s, %(c2)s)
ON CONFLICT (c1) DO UPDATE SET c1 = excluded.c1, c2 = excluded.c2
.. versionadded:: 1.4.21
:param \*ctes: zero or more :class:`.CTE` constructs.
.. versionchanged:: 2.0 Multiple CTE instances are accepted
:param nest_here: if True, the given CTE or CTEs will be rendered
as though they specified the :paramref:`.HasCTE.cte.nesting` flag
to ``True`` when they were added to this :class:`.HasCTE`.
Assuming the given CTEs are not referenced in an outer-enclosing
statement as well, the CTEs given should render at the level of
this statement when this flag is given.
.. versionadded:: 2.0
.. seealso::
:paramref:`.HasCTE.cte.nesting`
"""
opt = _CTEOpts(
nest_here,
)
for cte in ctes:
cte = coercions.expect(roles.IsCTERole, cte)
self._independent_ctes += (cte,)
self._independent_ctes_opts += (opt,)
return self
def cte(
self,
name: Optional[str] = None,
recursive: bool = False,
nesting: bool = False,
) -> CTE:
r"""Return a new :class:`_expression.CTE`,
or Common Table Expression instance.
Common table expressions are a SQL standard whereby SELECT
statements can draw upon secondary statements specified along
with the primary statement, using a clause called "WITH".
Special semantics regarding UNION can also be employed to
allow "recursive" queries, where a SELECT statement can draw
upon the set of rows that have previously been selected.
CTEs can also be applied to DML constructs UPDATE, INSERT
and DELETE on some databases, both as a source of CTE rows
when combined with RETURNING, as well as a consumer of
CTE rows.
SQLAlchemy detects :class:`_expression.CTE` objects, which are treated
similarly to :class:`_expression.Alias` objects, as special elements
to be delivered to the FROM clause of the statement as well
as to a WITH clause at the top of the statement.
For special prefixes such as PostgreSQL "MATERIALIZED" and
"NOT MATERIALIZED", the :meth:`_expression.CTE.prefix_with`
method may be
used to establish these.
.. versionchanged:: 1.3.13 Added support for prefixes.
In particular - MATERIALIZED and NOT MATERIALIZED.
:param name: name given to the common table expression. Like
:meth:`_expression.FromClause.alias`, the name can be left as
``None`` in which case an anonymous symbol will be used at query
compile time.
:param recursive: if ``True``, will render ``WITH RECURSIVE``.
A recursive common table expression is intended to be used in
conjunction with UNION ALL in order to derive rows
from those already selected.
:param nesting: if ``True``, will render the CTE locally to the
statement in which it is referenced. For more complex scenarios,
the :meth:`.HasCTE.add_cte` method using the
:paramref:`.HasCTE.add_cte.nest_here`
parameter may also be used to more carefully
control the exact placement of a particular CTE.
.. versionadded:: 1.4.24
.. seealso::
:meth:`.HasCTE.add_cte`
The following examples include two from PostgreSQL's documentation at
https://www.postgresql.org/docs/current/static/queries-with.html,
as well as additional examples.
Example 1, non recursive::
from sqlalchemy import (Table, Column, String, Integer,
MetaData, select, func)
metadata = MetaData()
orders = Table('orders', metadata,
Column('region', String),
Column('amount', Integer),
Column('product', String),
Column('quantity', Integer)
)
regional_sales = select(
orders.c.region,
func.sum(orders.c.amount).label('total_sales')
).group_by(orders.c.region).cte("regional_sales")
top_regions = select(regional_sales.c.region).\
where(
regional_sales.c.total_sales >
select(
func.sum(regional_sales.c.total_sales) / 10
)
).cte("top_regions")
statement = select(
orders.c.region,
orders.c.product,
func.sum(orders.c.quantity).label("product_units"),
func.sum(orders.c.amount).label("product_sales")
).where(orders.c.region.in_(
select(top_regions.c.region)
)).group_by(orders.c.region, orders.c.product)
result = conn.execute(statement).fetchall()
Example 2, WITH RECURSIVE::
from sqlalchemy import (Table, Column, String, Integer,
MetaData, select, func)
metadata = MetaData()
parts = Table('parts', metadata,
Column('part', String),
Column('sub_part', String),
Column('quantity', Integer),
)
included_parts = select(\
parts.c.sub_part, parts.c.part, parts.c.quantity\
).\
where(parts.c.part=='our part').\
cte(recursive=True)
incl_alias = included_parts.alias()
parts_alias = parts.alias()
included_parts = included_parts.union_all(
select(
parts_alias.c.sub_part,
parts_alias.c.part,
parts_alias.c.quantity
).\
where(parts_alias.c.part==incl_alias.c.sub_part)
)
statement = select(
included_parts.c.sub_part,
func.sum(included_parts.c.quantity).
label('total_quantity')
).\
group_by(included_parts.c.sub_part)
result = conn.execute(statement).fetchall()
Example 3, an upsert using UPDATE and INSERT with CTEs::
from datetime import date
from sqlalchemy import (MetaData, Table, Column, Integer,
Date, select, literal, and_, exists)
metadata = MetaData()
visitors = Table('visitors', metadata,
Column('product_id', Integer, primary_key=True),
Column('date', Date, primary_key=True),
Column('count', Integer),
)
# add 5 visitors for the product_id == 1
product_id = 1
day = date.today()
count = 5
update_cte = (
visitors.update()
.where(and_(visitors.c.product_id == product_id,
visitors.c.date == day))
.values(count=visitors.c.count + count)
.returning(literal(1))
.cte('update_cte')
)
upsert = visitors.insert().from_select(
[visitors.c.product_id, visitors.c.date, visitors.c.count],
select(literal(product_id), literal(day), literal(count))
.where(~exists(update_cte.select()))
)
connection.execute(upsert)
Example 4, Nesting CTE (SQLAlchemy 1.4.24 and above)::
value_a = select(
literal("root").label("n")
).cte("value_a")
# A nested CTE with the same name as the root one
value_a_nested = select(
literal("nesting").label("n")
).cte("value_a", nesting=True)
# Nesting CTEs takes ascendency locally
# over the CTEs at a higher level
value_b = select(value_a_nested.c.n).cte("value_b")
value_ab = select(value_a.c.n.label("a"), value_b.c.n.label("b"))
The above query will render the second CTE nested inside the first,
shown with inline parameters below as::
WITH
value_a AS
(SELECT 'root' AS n),
value_b AS
(WITH value_a AS
(SELECT 'nesting' AS n)
SELECT value_a.n AS n FROM value_a)
SELECT value_a.n AS a, value_b.n AS b
FROM value_a, value_b
The same CTE can be set up using the :meth:`.HasCTE.add_cte` method
as follows (SQLAlchemy 2.0 and above)::
value_a = select(
literal("root").label("n")
).cte("value_a")
# A nested CTE with the same name as the root one
value_a_nested = select(
literal("nesting").label("n")
).cte("value_a")
# Nesting CTEs takes ascendency locally
# over the CTEs at a higher level
value_b = (
select(value_a_nested.c.n).
add_cte(value_a_nested, nest_here=True).
cte("value_b")
)
value_ab = select(value_a.c.n.label("a"), value_b.c.n.label("b"))
Example 5, Non-Linear CTE (SQLAlchemy 1.4.28 and above)::
edge = Table(
"edge",
metadata,
Column("id", Integer, primary_key=True),
Column("left", Integer),
Column("right", Integer),
)
root_node = select(literal(1).label("node")).cte(
"nodes", recursive=True
)
left_edge = select(edge.c.left).join(
root_node, edge.c.right == root_node.c.node
)
right_edge = select(edge.c.right).join(
root_node, edge.c.left == root_node.c.node
)
subgraph_cte = root_node.union(left_edge, right_edge)
subgraph = select(subgraph_cte)
The above query will render 2 UNIONs inside the recursive CTE::
WITH RECURSIVE nodes(node) AS (
SELECT 1 AS node
UNION
SELECT edge."left" AS "left"
FROM edge JOIN nodes ON edge."right" = nodes.node
UNION
SELECT edge."right" AS "right"
FROM edge JOIN nodes ON edge."left" = nodes.node
)
SELECT nodes.node FROM nodes
.. seealso::
:meth:`_orm.Query.cte` - ORM version of
:meth:`_expression.HasCTE.cte`.
"""
return CTE._construct(
self, name=name, recursive=recursive, nesting=nesting
)
class Subquery(AliasedReturnsRows):
"""Represent a subquery of a SELECT.
A :class:`.Subquery` is created by invoking the
:meth:`_expression.SelectBase.subquery` method, or for convenience the
:meth:`_expression.SelectBase.alias` method, on any
:class:`_expression.SelectBase` subclass
which includes :class:`_expression.Select`,
:class:`_expression.CompoundSelect`, and
:class:`_expression.TextualSelect`. As rendered in a FROM clause,
it represents the
body of the SELECT statement inside of parenthesis, followed by the usual
"AS <somename>" that defines all "alias" objects.
The :class:`.Subquery` object is very similar to the
:class:`_expression.Alias`
object and can be used in an equivalent way. The difference between
:class:`_expression.Alias` and :class:`.Subquery` is that
:class:`_expression.Alias` always
contains a :class:`_expression.FromClause` object whereas
:class:`.Subquery`
always contains a :class:`_expression.SelectBase` object.
.. versionadded:: 1.4 The :class:`.Subquery` class was added which now
serves the purpose of providing an aliased version of a SELECT
statement.
"""
__visit_name__ = "subquery"
_is_subquery = True
inherit_cache = True
element: SelectBase
@classmethod
def _factory(
cls, selectable: SelectBase, name: Optional[str] = None
) -> Subquery:
"""Return a :class:`.Subquery` object."""
return coercions.expect(
roles.SelectStatementRole, selectable
).subquery(name=name)
@util.deprecated(
"1.4",
"The :meth:`.Subquery.as_scalar` method, which was previously "
"``Alias.as_scalar()`` prior to version 1.4, is deprecated and "
"will be removed in a future release; Please use the "
":meth:`_expression.Select.scalar_subquery` method of the "
":func:`_expression.select` "
"construct before constructing a subquery object, or with the ORM "
"use the :meth:`_query.Query.scalar_subquery` method.",
)
def as_scalar(self) -> ScalarSelect[Any]:
return self.element.set_label_style(LABEL_STYLE_NONE).scalar_subquery()
class FromGrouping(GroupedElement, FromClause):
"""Represent a grouping of a FROM clause"""
_traverse_internals: _TraverseInternalsType = [
("element", InternalTraversal.dp_clauseelement)
]
element: FromClause
def __init__(self, element: FromClause):
self.element = coercions.expect(roles.FromClauseRole, element)
def _init_collections(self) -> None:
pass
@util.ro_non_memoized_property
def columns(
self,
) -> ReadOnlyColumnCollection[str, KeyedColumnElement[Any]]:
return self.element.columns
@util.ro_non_memoized_property
def c(self) -> ReadOnlyColumnCollection[str, KeyedColumnElement[Any]]:
return self.element.columns
@property
def primary_key(self) -> Iterable[NamedColumn[Any]]:
return self.element.primary_key
@property
def foreign_keys(self) -> Iterable[ForeignKey]:
return self.element.foreign_keys
def is_derived_from(self, fromclause: Optional[FromClause]) -> bool:
return self.element.is_derived_from(fromclause)
def alias(
self, name: Optional[str] = None, flat: bool = False
) -> NamedFromGrouping:
return NamedFromGrouping(self.element.alias(name=name, flat=flat))
def _anonymous_fromclause(self, **kw: Any) -> FromGrouping:
return FromGrouping(self.element._anonymous_fromclause(**kw))
@util.ro_non_memoized_property
def _hide_froms(self) -> Iterable[FromClause]:
return self.element._hide_froms
@util.ro_non_memoized_property
def _from_objects(self) -> List[FromClause]:
return self.element._from_objects
def __getstate__(self) -> Dict[str, FromClause]:
return {"element": self.element}
def __setstate__(self, state: Dict[str, FromClause]) -> None:
self.element = state["element"]
if TYPE_CHECKING:
def self_group(
self, against: Optional[OperatorType] = None
) -> Self: ...
class NamedFromGrouping(FromGrouping, NamedFromClause):
"""represent a grouping of a named FROM clause
.. versionadded:: 2.0
"""
inherit_cache = True
if TYPE_CHECKING:
def self_group(
self, against: Optional[OperatorType] = None
) -> Self: ...
class TableClause(roles.DMLTableRole, Immutable, NamedFromClause):
"""Represents a minimal "table" construct.
This is a lightweight table object that has only a name, a
collection of columns, which are typically produced
by the :func:`_expression.column` function, and a schema::
from sqlalchemy import table, column
user = table("user",
column("id"),
column("name"),
column("description"),
)
The :class:`_expression.TableClause` construct serves as the base for
the more commonly used :class:`_schema.Table` object, providing
the usual set of :class:`_expression.FromClause` services including
the ``.c.`` collection and statement generation methods.
It does **not** provide all the additional schema-level services
of :class:`_schema.Table`, including constraints, references to other
tables, or support for :class:`_schema.MetaData`-level services.
It's useful
on its own as an ad-hoc construct used to generate quick SQL
statements when a more fully fledged :class:`_schema.Table`
is not on hand.
"""
__visit_name__ = "table"
_traverse_internals: _TraverseInternalsType = [
(
"columns",
InternalTraversal.dp_fromclause_canonical_column_collection,
),
("name", InternalTraversal.dp_string),
("schema", InternalTraversal.dp_string),
]
_is_table = True
fullname: str
implicit_returning = False
""":class:`_expression.TableClause`
doesn't support having a primary key or column
-level defaults, so implicit returning doesn't apply."""
@util.ro_memoized_property
def _autoincrement_column(self) -> Optional[ColumnClause[Any]]:
"""No PK or default support so no autoincrement column."""
return None
def __init__(self, name: str, *columns: ColumnClause[Any], **kw: Any):
super().__init__()
self.name = name
self._columns = DedupeColumnCollection()
self.primary_key = ColumnSet() # type: ignore
self.foreign_keys = set() # type: ignore
for c in columns:
self.append_column(c)
schema = kw.pop("schema", None)
if schema is not None:
self.schema = schema
if self.schema is not None:
self.fullname = "%s.%s" % (self.schema, self.name)
else:
self.fullname = self.name
if kw:
raise exc.ArgumentError("Unsupported argument(s): %s" % list(kw))
if TYPE_CHECKING:
@util.ro_non_memoized_property
def columns(
self,
) -> ReadOnlyColumnCollection[str, ColumnClause[Any]]: ...
@util.ro_non_memoized_property
def c(self) -> ReadOnlyColumnCollection[str, ColumnClause[Any]]: ...
def __str__(self) -> str:
if self.schema is not None:
return self.schema + "." + self.name
else:
return self.name
def _refresh_for_new_column(self, column: ColumnElement[Any]) -> None:
pass
def _init_collections(self) -> None:
pass
@util.ro_memoized_property
def description(self) -> str:
return self.name
def append_column(self, c: ColumnClause[Any]) -> None:
existing = c.table
if existing is not None and existing is not self:
raise exc.ArgumentError(
"column object '%s' already assigned to table '%s'"
% (c.key, existing)
)
self._columns.add(c)
c.table = self
@util.preload_module("sqlalchemy.sql.dml")
def insert(self) -> util.preloaded.sql_dml.Insert:
"""Generate an :class:`_sql.Insert` construct against this
:class:`_expression.TableClause`.
E.g.::
table.insert().values(name='foo')
See :func:`_expression.insert` for argument and usage information.
"""
return util.preloaded.sql_dml.Insert(self)
@util.preload_module("sqlalchemy.sql.dml")
def update(self) -> Update:
"""Generate an :func:`_expression.update` construct against this
:class:`_expression.TableClause`.
E.g.::
table.update().where(table.c.id==7).values(name='foo')
See :func:`_expression.update` for argument and usage information.
"""
return util.preloaded.sql_dml.Update(
self,
)
@util.preload_module("sqlalchemy.sql.dml")
def delete(self) -> Delete:
"""Generate a :func:`_expression.delete` construct against this
:class:`_expression.TableClause`.
E.g.::
table.delete().where(table.c.id==7)
See :func:`_expression.delete` for argument and usage information.
"""
return util.preloaded.sql_dml.Delete(self)
@util.ro_non_memoized_property
def _from_objects(self) -> List[FromClause]:
return [self]
ForUpdateParameter = Union["ForUpdateArg", None, bool, Dict[str, Any]]
class ForUpdateArg(ClauseElement):
_traverse_internals: _TraverseInternalsType = [
("of", InternalTraversal.dp_clauseelement_list),
("nowait", InternalTraversal.dp_boolean),
("read", InternalTraversal.dp_boolean),
("skip_locked", InternalTraversal.dp_boolean),
("key_share", InternalTraversal.dp_boolean),
]
of: Optional[Sequence[ClauseElement]]
nowait: bool
read: bool
skip_locked: bool
@classmethod
def _from_argument(
cls, with_for_update: ForUpdateParameter
) -> Optional[ForUpdateArg]:
if isinstance(with_for_update, ForUpdateArg):
return with_for_update
elif with_for_update in (None, False):
return None
elif with_for_update is True:
return ForUpdateArg()
else:
return ForUpdateArg(**cast("Dict[str, Any]", with_for_update))
def __eq__(self, other: Any) -> bool:
return (
isinstance(other, ForUpdateArg)
and other.nowait == self.nowait
and other.read == self.read
and other.skip_locked == self.skip_locked
and other.key_share == self.key_share
and other.of is self.of
)
def __ne__(self, other: Any) -> bool:
return not self.__eq__(other)
def __hash__(self) -> int:
return id(self)
def __init__(
self,
*,
nowait: bool = False,
read: bool = False,
of: Optional[_ForUpdateOfArgument] = None,
skip_locked: bool = False,
key_share: bool = False,
):
"""Represents arguments specified to
:meth:`_expression.Select.for_update`.
"""
self.nowait = nowait
self.read = read
self.skip_locked = skip_locked
self.key_share = key_share
if of is not None:
self.of = [
coercions.expect(roles.ColumnsClauseRole, elem)
for elem in util.to_list(of)
]
else:
self.of = None
class Values(roles.InElementRole, Generative, LateralFromClause):
"""Represent a ``VALUES`` construct that can be used as a FROM element
in a statement.
The :class:`_expression.Values` object is created from the
:func:`_expression.values` function.
.. versionadded:: 1.4
"""
__visit_name__ = "values"
_data: Tuple[Sequence[Tuple[Any, ...]], ...] = ()
_unnamed: bool
_traverse_internals: _TraverseInternalsType = [
("_column_args", InternalTraversal.dp_clauseelement_list),
("_data", InternalTraversal.dp_dml_multi_values),
("name", InternalTraversal.dp_string),
("literal_binds", InternalTraversal.dp_boolean),
]
def __init__(
self,
*columns: ColumnClause[Any],
name: Optional[str] = None,
literal_binds: bool = False,
):
super().__init__()
self._column_args = columns
if name is None:
self._unnamed = True
self.name = _anonymous_label.safe_construct(id(self), "anon")
else:
self._unnamed = False
self.name = name
self.literal_binds = literal_binds
self.named_with_column = not self._unnamed
@property
def _column_types(self) -> List[TypeEngine[Any]]:
return [col.type for col in self._column_args]
@_generative
def alias(self, name: Optional[str] = None, flat: bool = False) -> Self:
"""Return a new :class:`_expression.Values`
construct that is a copy of this
one with the given name.
This method is a VALUES-specific specialization of the
:meth:`_expression.FromClause.alias` method.
.. seealso::
:ref:`tutorial_using_aliases`
:func:`_expression.alias`
"""
non_none_name: str
if name is None:
non_none_name = _anonymous_label.safe_construct(id(self), "anon")
else:
non_none_name = name
self.name = non_none_name
self.named_with_column = True
self._unnamed = False
return self
@_generative
def lateral(self, name: Optional[str] = None) -> LateralFromClause:
"""Return a new :class:`_expression.Values` with the lateral flag set,
so that
it renders as LATERAL.
.. seealso::
:func:`_expression.lateral`
"""
non_none_name: str
if name is None:
non_none_name = self.name
else:
non_none_name = name
self._is_lateral = True
self.name = non_none_name
self._unnamed = False
return self
@_generative
def data(self, values: Sequence[Tuple[Any, ...]]) -> Self:
"""Return a new :class:`_expression.Values` construct,
adding the given data to the data list.
E.g.::
my_values = my_values.data([(1, 'value 1'), (2, 'value2')])
:param values: a sequence (i.e. list) of tuples that map to the
column expressions given in the :class:`_expression.Values`
constructor.
"""
self._data += (values,)
return self
def scalar_values(self) -> ScalarValues:
"""Returns a scalar ``VALUES`` construct that can be used as a
COLUMN element in a statement.
.. versionadded:: 2.0.0b4
"""
return ScalarValues(self._column_args, self._data, self.literal_binds)
def _populate_column_collection(self) -> None:
for c in self._column_args:
if c.table is not None and c.table is not self:
_, c = c._make_proxy(self)
else:
# if the column was used in other contexts, ensure
# no memoizations of other FROM clauses.
# see test_values.py -> test_auto_proxy_select_direct_col
c._reset_memoizations()
self._columns.add(c)
c.table = self
@util.ro_non_memoized_property
def _from_objects(self) -> List[FromClause]:
return [self]
class ScalarValues(roles.InElementRole, GroupedElement, ColumnElement[Any]):
"""Represent a scalar ``VALUES`` construct that can be used as a
COLUMN element in a statement.
The :class:`_expression.ScalarValues` object is created from the
:meth:`_expression.Values.scalar_values` method. It's also
automatically generated when a :class:`_expression.Values` is used in
an ``IN`` or ``NOT IN`` condition.
.. versionadded:: 2.0.0b4
"""
__visit_name__ = "scalar_values"
_traverse_internals: _TraverseInternalsType = [
("_column_args", InternalTraversal.dp_clauseelement_list),
("_data", InternalTraversal.dp_dml_multi_values),
("literal_binds", InternalTraversal.dp_boolean),
]
def __init__(
self,
columns: Sequence[ColumnClause[Any]],
data: Tuple[Sequence[Tuple[Any, ...]], ...],
literal_binds: bool,
):
super().__init__()
self._column_args = columns
self._data = data
self.literal_binds = literal_binds
@property
def _column_types(self) -> List[TypeEngine[Any]]:
return [col.type for col in self._column_args]
def __clause_element__(self) -> ScalarValues:
return self
if TYPE_CHECKING:
def self_group(
self, against: Optional[OperatorType] = None
) -> Self: ...
class SelectBase(
roles.SelectStatementRole,
roles.DMLSelectRole,
roles.CompoundElementRole,
roles.InElementRole,
HasCTE,
SupportsCloneAnnotations,
Selectable,
):
"""Base class for SELECT statements.
This includes :class:`_expression.Select`,
:class:`_expression.CompoundSelect` and
:class:`_expression.TextualSelect`.
"""
_is_select_base = True
is_select = True
_label_style: SelectLabelStyle = LABEL_STYLE_NONE
def _refresh_for_new_column(self, column: ColumnElement[Any]) -> None:
self._reset_memoizations()
@util.ro_non_memoized_property
def selected_columns(
self,
) -> ColumnCollection[str, ColumnElement[Any]]:
"""A :class:`_expression.ColumnCollection`
representing the columns that
this SELECT statement or similar construct returns in its result set.
This collection differs from the :attr:`_expression.FromClause.columns`
collection of a :class:`_expression.FromClause` in that the columns
within this collection cannot be directly nested inside another SELECT
statement; a subquery must be applied first which provides for the
necessary parenthesization required by SQL.
.. note::
The :attr:`_sql.SelectBase.selected_columns` collection does not
include expressions established in the columns clause using the
:func:`_sql.text` construct; these are silently omitted from the
collection. To use plain textual column expressions inside of a
:class:`_sql.Select` construct, use the :func:`_sql.literal_column`
construct.
.. seealso::
:attr:`_sql.Select.selected_columns`
.. versionadded:: 1.4
"""
raise NotImplementedError()
def _generate_fromclause_column_proxies(
self,
subquery: FromClause,
*,
proxy_compound_columns: Optional[
Iterable[Sequence[ColumnElement[Any]]]
] = None,
) -> None:
raise NotImplementedError()
@util.ro_non_memoized_property
def _all_selected_columns(self) -> _SelectIterable:
"""A sequence of expressions that correspond to what is rendered
in the columns clause, including :class:`_sql.TextClause`
constructs.
.. versionadded:: 1.4.12
.. seealso::
:attr:`_sql.SelectBase.exported_columns`
"""
raise NotImplementedError()
@property
def exported_columns(
self,
) -> ReadOnlyColumnCollection[str, ColumnElement[Any]]:
"""A :class:`_expression.ColumnCollection`
that represents the "exported"
columns of this :class:`_expression.Selectable`, not including
:class:`_sql.TextClause` constructs.
The "exported" columns for a :class:`_expression.SelectBase`
object are synonymous
with the :attr:`_expression.SelectBase.selected_columns` collection.
.. versionadded:: 1.4
.. seealso::
:attr:`_expression.Select.exported_columns`
:attr:`_expression.Selectable.exported_columns`
:attr:`_expression.FromClause.exported_columns`
"""
return self.selected_columns.as_readonly()
@property
@util.deprecated(
"1.4",
"The :attr:`_expression.SelectBase.c` and "
":attr:`_expression.SelectBase.columns` attributes "
"are deprecated and will be removed in a future release; these "
"attributes implicitly create a subquery that should be explicit. "
"Please call :meth:`_expression.SelectBase.subquery` "
"first in order to create "
"a subquery, which then contains this attribute. To access the "
"columns that this SELECT object SELECTs "
"from, use the :attr:`_expression.SelectBase.selected_columns` "
"attribute.",
)
def c(self) -> ReadOnlyColumnCollection[str, KeyedColumnElement[Any]]:
return self._implicit_subquery.columns
@property
def columns(
self,
) -> ReadOnlyColumnCollection[str, KeyedColumnElement[Any]]:
return self.c
def get_label_style(self) -> SelectLabelStyle:
"""
Retrieve the current label style.
Implemented by subclasses.
"""
raise NotImplementedError()
def set_label_style(self, style: SelectLabelStyle) -> Self:
"""Return a new selectable with the specified label style.
Implemented by subclasses.
"""
raise NotImplementedError()
@util.deprecated(
"1.4",
"The :meth:`_expression.SelectBase.select` method is deprecated "
"and will be removed in a future release; this method implicitly "
"creates a subquery that should be explicit. "
"Please call :meth:`_expression.SelectBase.subquery` "
"first in order to create "
"a subquery, which then can be selected.",
)
def select(self, *arg: Any, **kw: Any) -> Select[Any]:
return self._implicit_subquery.select(*arg, **kw)
@HasMemoized.memoized_attribute
def _implicit_subquery(self) -> Subquery:
return self.subquery()
def _scalar_type(self) -> TypeEngine[Any]:
raise NotImplementedError()
@util.deprecated(
"1.4",
"The :meth:`_expression.SelectBase.as_scalar` "
"method is deprecated and will be "
"removed in a future release. Please refer to "
":meth:`_expression.SelectBase.scalar_subquery`.",
)
def as_scalar(self) -> ScalarSelect[Any]:
return self.scalar_subquery()
def exists(self) -> Exists:
"""Return an :class:`_sql.Exists` representation of this selectable,
which can be used as a column expression.
The returned object is an instance of :class:`_sql.Exists`.
.. seealso::
:func:`_sql.exists`
:ref:`tutorial_exists` - in the :term:`2.0 style` tutorial.
.. versionadded:: 1.4
"""
return Exists(self)
def scalar_subquery(self) -> ScalarSelect[Any]:
"""Return a 'scalar' representation of this selectable, which can be
used as a column expression.
The returned object is an instance of :class:`_sql.ScalarSelect`.
Typically, a select statement which has only one column in its columns
clause is eligible to be used as a scalar expression. The scalar
subquery can then be used in the WHERE clause or columns clause of
an enclosing SELECT.
Note that the scalar subquery differentiates from the FROM-level
subquery that can be produced using the
:meth:`_expression.SelectBase.subquery`
method.
.. versionchanged: 1.4 - the ``.as_scalar()`` method was renamed to
:meth:`_expression.SelectBase.scalar_subquery`.
.. seealso::
:ref:`tutorial_scalar_subquery` - in the 2.0 tutorial
"""
if self._label_style is not LABEL_STYLE_NONE:
self = self.set_label_style(LABEL_STYLE_NONE)
return ScalarSelect(self)
def label(self, name: Optional[str]) -> Label[Any]:
"""Return a 'scalar' representation of this selectable, embedded as a
subquery with a label.
.. seealso::
:meth:`_expression.SelectBase.scalar_subquery`.
"""
return self.scalar_subquery().label(name)
def lateral(self, name: Optional[str] = None) -> LateralFromClause:
"""Return a LATERAL alias of this :class:`_expression.Selectable`.
The return value is the :class:`_expression.Lateral` construct also
provided by the top-level :func:`_expression.lateral` function.
.. seealso::
:ref:`tutorial_lateral_correlation` - overview of usage.
"""
return Lateral._factory(self, name)
def subquery(self, name: Optional[str] = None) -> Subquery:
"""Return a subquery of this :class:`_expression.SelectBase`.
A subquery is from a SQL perspective a parenthesized, named
construct that can be placed in the FROM clause of another
SELECT statement.
Given a SELECT statement such as::
stmt = select(table.c.id, table.c.name)
The above statement might look like::
SELECT table.id, table.name FROM table
The subquery form by itself renders the same way, however when
embedded into the FROM clause of another SELECT statement, it becomes
a named sub-element::
subq = stmt.subquery()
new_stmt = select(subq)
The above renders as::
SELECT anon_1.id, anon_1.name
FROM (SELECT table.id, table.name FROM table) AS anon_1
Historically, :meth:`_expression.SelectBase.subquery`
is equivalent to calling
the :meth:`_expression.FromClause.alias`
method on a FROM object; however,
as a :class:`_expression.SelectBase`
object is not directly FROM object,
the :meth:`_expression.SelectBase.subquery`
method provides clearer semantics.
.. versionadded:: 1.4
"""
return Subquery._construct(
self._ensure_disambiguated_names(), name=name
)
def _ensure_disambiguated_names(self) -> Self:
"""Ensure that the names generated by this selectbase will be
disambiguated in some way, if possible.
"""
raise NotImplementedError()
def alias(
self, name: Optional[str] = None, flat: bool = False
) -> Subquery:
"""Return a named subquery against this
:class:`_expression.SelectBase`.
For a :class:`_expression.SelectBase` (as opposed to a
:class:`_expression.FromClause`),
this returns a :class:`.Subquery` object which behaves mostly the
same as the :class:`_expression.Alias` object that is used with a
:class:`_expression.FromClause`.
.. versionchanged:: 1.4 The :meth:`_expression.SelectBase.alias`
method is now
a synonym for the :meth:`_expression.SelectBase.subquery` method.
"""
return self.subquery(name=name)
_SB = TypeVar("_SB", bound=SelectBase)
class SelectStatementGrouping(GroupedElement, SelectBase, Generic[_SB]):
"""Represent a grouping of a :class:`_expression.SelectBase`.
This differs from :class:`.Subquery` in that we are still
an "inner" SELECT statement, this is strictly for grouping inside of
compound selects.
"""
__visit_name__ = "select_statement_grouping"
_traverse_internals: _TraverseInternalsType = [
("element", InternalTraversal.dp_clauseelement)
] + SupportsCloneAnnotations._clone_annotations_traverse_internals
_is_select_container = True
element: _SB
def __init__(self, element: _SB) -> None:
self.element = cast(
_SB, coercions.expect(roles.SelectStatementRole, element)
)
def _ensure_disambiguated_names(self) -> SelectStatementGrouping[_SB]:
new_element = self.element._ensure_disambiguated_names()
if new_element is not self.element:
return SelectStatementGrouping(new_element)
else:
return self
def get_label_style(self) -> SelectLabelStyle:
return self.element.get_label_style()
def set_label_style(
self, label_style: SelectLabelStyle
) -> SelectStatementGrouping[_SB]:
return SelectStatementGrouping(
self.element.set_label_style(label_style)
)
@property
def select_statement(self) -> _SB:
return self.element
def self_group(self, against: Optional[OperatorType] = None) -> Self:
return self
if TYPE_CHECKING:
def _ungroup(self) -> _SB: ...
# def _generate_columns_plus_names(
# self, anon_for_dupe_key: bool
# ) -> List[Tuple[str, str, str, ColumnElement[Any], bool]]:
# return self.element._generate_columns_plus_names(anon_for_dupe_key)
def _generate_fromclause_column_proxies(
self,
subquery: FromClause,
*,
proxy_compound_columns: Optional[
Iterable[Sequence[ColumnElement[Any]]]
] = None,
) -> None:
self.element._generate_fromclause_column_proxies(
subquery, proxy_compound_columns=proxy_compound_columns
)
@util.ro_non_memoized_property
def _all_selected_columns(self) -> _SelectIterable:
return self.element._all_selected_columns
@util.ro_non_memoized_property
def selected_columns(self) -> ColumnCollection[str, ColumnElement[Any]]:
"""A :class:`_expression.ColumnCollection`
representing the columns that
the embedded SELECT statement returns in its result set, not including
:class:`_sql.TextClause` constructs.
.. versionadded:: 1.4
.. seealso::
:attr:`_sql.Select.selected_columns`
"""
return self.element.selected_columns
@util.ro_non_memoized_property
def _from_objects(self) -> List[FromClause]:
return self.element._from_objects
def add_cte(self, *ctes: CTE, nest_here: bool = False) -> Self:
# SelectStatementGrouping not generative: has no attribute '_generate'
raise NotImplementedError
class GenerativeSelect(SelectBase, Generative):
"""Base class for SELECT statements where additional elements can be
added.
This serves as the base for :class:`_expression.Select` and
:class:`_expression.CompoundSelect`
where elements such as ORDER BY, GROUP BY can be added and column
rendering can be controlled. Compare to
:class:`_expression.TextualSelect`, which,
while it subclasses :class:`_expression.SelectBase`
and is also a SELECT construct,
represents a fixed textual string which cannot be altered at this level,
only wrapped as a subquery.
"""
_order_by_clauses: Tuple[ColumnElement[Any], ...] = ()
_group_by_clauses: Tuple[ColumnElement[Any], ...] = ()
_limit_clause: Optional[ColumnElement[Any]] = None
_offset_clause: Optional[ColumnElement[Any]] = None
_fetch_clause: Optional[ColumnElement[Any]] = None
_fetch_clause_options: Optional[Dict[str, bool]] = None
_for_update_arg: Optional[ForUpdateArg] = None
def __init__(self, _label_style: SelectLabelStyle = LABEL_STYLE_DEFAULT):
self._label_style = _label_style
@_generative
def with_for_update(
self,
*,
nowait: bool = False,
read: bool = False,
of: Optional[_ForUpdateOfArgument] = None,
skip_locked: bool = False,
key_share: bool = False,
) -> Self:
"""Specify a ``FOR UPDATE`` clause for this
:class:`_expression.GenerativeSelect`.
E.g.::
stmt = select(table).with_for_update(nowait=True)
On a database like PostgreSQL or Oracle, the above would render a
statement like::
SELECT table.a, table.b FROM table FOR UPDATE NOWAIT
on other backends, the ``nowait`` option is ignored and instead
would produce::
SELECT table.a, table.b FROM table FOR UPDATE
When called with no arguments, the statement will render with
the suffix ``FOR UPDATE``. Additional arguments can then be
provided which allow for common database-specific
variants.
:param nowait: boolean; will render ``FOR UPDATE NOWAIT`` on Oracle
and PostgreSQL dialects.
:param read: boolean; will render ``LOCK IN SHARE MODE`` on MySQL,
``FOR SHARE`` on PostgreSQL. On PostgreSQL, when combined with
``nowait``, will render ``FOR SHARE NOWAIT``.
:param of: SQL expression or list of SQL expression elements,
(typically :class:`_schema.Column` objects or a compatible expression,
for some backends may also be a table expression) which will render
into a ``FOR UPDATE OF`` clause; supported by PostgreSQL, Oracle, some
MySQL versions and possibly others. May render as a table or as a
column depending on backend.
:param skip_locked: boolean, will render ``FOR UPDATE SKIP LOCKED``
on Oracle and PostgreSQL dialects or ``FOR SHARE SKIP LOCKED`` if
``read=True`` is also specified.
:param key_share: boolean, will render ``FOR NO KEY UPDATE``,
or if combined with ``read=True`` will render ``FOR KEY SHARE``,
on the PostgreSQL dialect.
"""
self._for_update_arg = ForUpdateArg(
nowait=nowait,
read=read,
of=of,
skip_locked=skip_locked,
key_share=key_share,
)
return self
def get_label_style(self) -> SelectLabelStyle:
"""
Retrieve the current label style.
.. versionadded:: 1.4
"""
return self._label_style
def set_label_style(self, style: SelectLabelStyle) -> Self:
"""Return a new selectable with the specified label style.
There are three "label styles" available,
:attr:`_sql.SelectLabelStyle.LABEL_STYLE_DISAMBIGUATE_ONLY`,
:attr:`_sql.SelectLabelStyle.LABEL_STYLE_TABLENAME_PLUS_COL`, and
:attr:`_sql.SelectLabelStyle.LABEL_STYLE_NONE`. The default style is
:attr:`_sql.SelectLabelStyle.LABEL_STYLE_DISAMBIGUATE_ONLY`.
In modern SQLAlchemy, there is not generally a need to change the
labeling style, as per-expression labels are more effectively used by
making use of the :meth:`_sql.ColumnElement.label` method. In past
versions, :data:`_sql.LABEL_STYLE_TABLENAME_PLUS_COL` was used to
disambiguate same-named columns from different tables, aliases, or
subqueries; the newer :data:`_sql.LABEL_STYLE_DISAMBIGUATE_ONLY` now
applies labels only to names that conflict with an existing name so
that the impact of this labeling is minimal.
The rationale for disambiguation is mostly so that all column
expressions are available from a given :attr:`_sql.FromClause.c`
collection when a subquery is created.
.. versionadded:: 1.4 - the
:meth:`_sql.GenerativeSelect.set_label_style` method replaces the
previous combination of ``.apply_labels()``, ``.with_labels()`` and
``use_labels=True`` methods and/or parameters.
.. seealso::
:data:`_sql.LABEL_STYLE_DISAMBIGUATE_ONLY`
:data:`_sql.LABEL_STYLE_TABLENAME_PLUS_COL`
:data:`_sql.LABEL_STYLE_NONE`
:data:`_sql.LABEL_STYLE_DEFAULT`
"""
if self._label_style is not style:
self = self._generate()
self._label_style = style
return self
@property
def _group_by_clause(self) -> ClauseList:
"""ClauseList access to group_by_clauses for legacy dialects"""
return ClauseList._construct_raw(
operators.comma_op, self._group_by_clauses
)
@property
def _order_by_clause(self) -> ClauseList:
"""ClauseList access to order_by_clauses for legacy dialects"""
return ClauseList._construct_raw(
operators.comma_op, self._order_by_clauses
)
def _offset_or_limit_clause(
self,
element: _LimitOffsetType,
name: Optional[str] = None,
type_: Optional[_TypeEngineArgument[int]] = None,
) -> ColumnElement[Any]:
"""Convert the given value to an "offset or limit" clause.
This handles incoming integers and converts to an expression; if
an expression is already given, it is passed through.
"""
return coercions.expect(
roles.LimitOffsetRole, element, name=name, type_=type_
)
@overload
def _offset_or_limit_clause_asint(
self, clause: ColumnElement[Any], attrname: str
) -> NoReturn: ...
@overload
def _offset_or_limit_clause_asint(
self, clause: Optional[_OffsetLimitParam], attrname: str
) -> Optional[int]: ...
def _offset_or_limit_clause_asint(
self, clause: Optional[ColumnElement[Any]], attrname: str
) -> Union[NoReturn, Optional[int]]:
"""Convert the "offset or limit" clause of a select construct to an
integer.
This is only possible if the value is stored as a simple bound
parameter. Otherwise, a compilation error is raised.
"""
if clause is None:
return None
try:
value = clause._limit_offset_value
except AttributeError as err:
raise exc.CompileError(
"This SELECT structure does not use a simple "
"integer value for %s" % attrname
) from err
else:
return util.asint(value)
@property
def _limit(self) -> Optional[int]:
"""Get an integer value for the limit. This should only be used
by code that cannot support a limit as a BindParameter or
other custom clause as it will throw an exception if the limit
isn't currently set to an integer.
"""
return self._offset_or_limit_clause_asint(self._limit_clause, "limit")
def _simple_int_clause(self, clause: ClauseElement) -> bool:
"""True if the clause is a simple integer, False
if it is not present or is a SQL expression.
"""
return isinstance(clause, _OffsetLimitParam)
@property
def _offset(self) -> Optional[int]:
"""Get an integer value for the offset. This should only be used
by code that cannot support an offset as a BindParameter or
other custom clause as it will throw an exception if the
offset isn't currently set to an integer.
"""
return self._offset_or_limit_clause_asint(
self._offset_clause, "offset"
)
@property
def _has_row_limiting_clause(self) -> bool:
return (
self._limit_clause is not None
or self._offset_clause is not None
or self._fetch_clause is not None
)
@_generative
def limit(self, limit: _LimitOffsetType) -> Self:
"""Return a new selectable with the given LIMIT criterion
applied.
This is a numerical value which usually renders as a ``LIMIT``
expression in the resulting select. Backends that don't
support ``LIMIT`` will attempt to provide similar
functionality.
.. note::
The :meth:`_sql.GenerativeSelect.limit` method will replace
any clause applied with :meth:`_sql.GenerativeSelect.fetch`.
:param limit: an integer LIMIT parameter, or a SQL expression
that provides an integer result. Pass ``None`` to reset it.
.. seealso::
:meth:`_sql.GenerativeSelect.fetch`
:meth:`_sql.GenerativeSelect.offset`
"""
self._fetch_clause = self._fetch_clause_options = None
self._limit_clause = self._offset_or_limit_clause(limit)
return self
@_generative
def fetch(
self,
count: _LimitOffsetType,
with_ties: bool = False,
percent: bool = False,
) -> Self:
"""Return a new selectable with the given FETCH FIRST criterion
applied.
This is a numeric value which usually renders as
``FETCH {FIRST | NEXT} [ count ] {ROW | ROWS} {ONLY | WITH TIES}``
expression in the resulting select. This functionality is
is currently implemented for Oracle, PostgreSQL, MSSQL.
Use :meth:`_sql.GenerativeSelect.offset` to specify the offset.
.. note::
The :meth:`_sql.GenerativeSelect.fetch` method will replace
any clause applied with :meth:`_sql.GenerativeSelect.limit`.
.. versionadded:: 1.4
:param count: an integer COUNT parameter, or a SQL expression
that provides an integer result. When ``percent=True`` this will
represent the percentage of rows to return, not the absolute value.
Pass ``None`` to reset it.
:param with_ties: When ``True``, the WITH TIES option is used
to return any additional rows that tie for the last place in the
result set according to the ``ORDER BY`` clause. The
``ORDER BY`` may be mandatory in this case. Defaults to ``False``
:param percent: When ``True``, ``count`` represents the percentage
of the total number of selected rows to return. Defaults to ``False``
.. seealso::
:meth:`_sql.GenerativeSelect.limit`
:meth:`_sql.GenerativeSelect.offset`
"""
self._limit_clause = None
if count is None:
self._fetch_clause = self._fetch_clause_options = None
else:
self._fetch_clause = self._offset_or_limit_clause(count)
self._fetch_clause_options = {
"with_ties": with_ties,
"percent": percent,
}
return self
@_generative
def offset(self, offset: _LimitOffsetType) -> Self:
"""Return a new selectable with the given OFFSET criterion
applied.
This is a numeric value which usually renders as an ``OFFSET``
expression in the resulting select. Backends that don't
support ``OFFSET`` will attempt to provide similar
functionality.
:param offset: an integer OFFSET parameter, or a SQL expression
that provides an integer result. Pass ``None`` to reset it.
.. seealso::
:meth:`_sql.GenerativeSelect.limit`
:meth:`_sql.GenerativeSelect.fetch`
"""
self._offset_clause = self._offset_or_limit_clause(offset)
return self
@_generative
@util.preload_module("sqlalchemy.sql.util")
def slice(
self,
start: int,
stop: int,
) -> Self:
"""Apply LIMIT / OFFSET to this statement based on a slice.
The start and stop indices behave like the argument to Python's
built-in :func:`range` function. This method provides an
alternative to using ``LIMIT``/``OFFSET`` to get a slice of the
query.
For example, ::
stmt = select(User).order_by(User).id.slice(1, 3)
renders as
.. sourcecode:: sql
SELECT users.id AS users_id,
users.name AS users_name
FROM users ORDER BY users.id
LIMIT ? OFFSET ?
(2, 1)
.. note::
The :meth:`_sql.GenerativeSelect.slice` method will replace
any clause applied with :meth:`_sql.GenerativeSelect.fetch`.
.. versionadded:: 1.4 Added the :meth:`_sql.GenerativeSelect.slice`
method generalized from the ORM.
.. seealso::
:meth:`_sql.GenerativeSelect.limit`
:meth:`_sql.GenerativeSelect.offset`
:meth:`_sql.GenerativeSelect.fetch`
"""
sql_util = util.preloaded.sql_util
self._fetch_clause = self._fetch_clause_options = None
self._limit_clause, self._offset_clause = sql_util._make_slice(
self._limit_clause, self._offset_clause, start, stop
)
return self
@_generative
def order_by(
self,
__first: Union[
Literal[None, _NoArg.NO_ARG],
_ColumnExpressionOrStrLabelArgument[Any],
] = _NoArg.NO_ARG,
*clauses: _ColumnExpressionOrStrLabelArgument[Any],
) -> Self:
r"""Return a new selectable with the given list of ORDER BY
criteria applied.
e.g.::
stmt = select(table).order_by(table.c.id, table.c.name)
Calling this method multiple times is equivalent to calling it once
with all the clauses concatenated. All existing ORDER BY criteria may
be cancelled by passing ``None`` by itself. New ORDER BY criteria may
then be added by invoking :meth:`_orm.Query.order_by` again, e.g.::
# will erase all ORDER BY and ORDER BY new_col alone
stmt = stmt.order_by(None).order_by(new_col)
:param \*clauses: a series of :class:`_expression.ColumnElement`
constructs
which will be used to generate an ORDER BY clause.
.. seealso::
:ref:`tutorial_order_by` - in the :ref:`unified_tutorial`
:ref:`tutorial_order_by_label` - in the :ref:`unified_tutorial`
"""
if not clauses and __first is None:
self._order_by_clauses = ()
elif __first is not _NoArg.NO_ARG:
self._order_by_clauses += tuple(
coercions.expect(
roles.OrderByRole, clause, apply_propagate_attrs=self
)
for clause in (__first,) + clauses
)
return self
@_generative
def group_by(
self,
__first: Union[
Literal[None, _NoArg.NO_ARG],
_ColumnExpressionOrStrLabelArgument[Any],
] = _NoArg.NO_ARG,
*clauses: _ColumnExpressionOrStrLabelArgument[Any],
) -> Self:
r"""Return a new selectable with the given list of GROUP BY
criterion applied.
All existing GROUP BY settings can be suppressed by passing ``None``.
e.g.::
stmt = select(table.c.name, func.max(table.c.stat)).\
group_by(table.c.name)
:param \*clauses: a series of :class:`_expression.ColumnElement`
constructs
which will be used to generate an GROUP BY clause.
.. seealso::
:ref:`tutorial_group_by_w_aggregates` - in the
:ref:`unified_tutorial`
:ref:`tutorial_order_by_label` - in the :ref:`unified_tutorial`
"""
if not clauses and __first is None:
self._group_by_clauses = ()
elif __first is not _NoArg.NO_ARG:
self._group_by_clauses += tuple(
coercions.expect(
roles.GroupByRole, clause, apply_propagate_attrs=self
)
for clause in (__first,) + clauses
)
return self
@CompileState.plugin_for("default", "compound_select")
class CompoundSelectState(CompileState):
@util.memoized_property
def _label_resolve_dict(
self,
) -> Tuple[
Dict[str, ColumnElement[Any]],
Dict[str, ColumnElement[Any]],
Dict[str, ColumnElement[Any]],
]:
# TODO: this is hacky and slow
hacky_subquery = self.statement.subquery()
hacky_subquery.named_with_column = False
d = {c.key: c for c in hacky_subquery.c}
return d, d, d
class _CompoundSelectKeyword(Enum):
UNION = "UNION"
UNION_ALL = "UNION ALL"
EXCEPT = "EXCEPT"
EXCEPT_ALL = "EXCEPT ALL"
INTERSECT = "INTERSECT"
INTERSECT_ALL = "INTERSECT ALL"
class CompoundSelect(HasCompileState, GenerativeSelect, ExecutableReturnsRows):
"""Forms the basis of ``UNION``, ``UNION ALL``, and other
SELECT-based set operations.
.. seealso::
:func:`_expression.union`
:func:`_expression.union_all`
:func:`_expression.intersect`
:func:`_expression.intersect_all`
:func:`_expression.except`
:func:`_expression.except_all`
"""
__visit_name__ = "compound_select"
_traverse_internals: _TraverseInternalsType = (
[
("selects", InternalTraversal.dp_clauseelement_list),
("_limit_clause", InternalTraversal.dp_clauseelement),
("_offset_clause", InternalTraversal.dp_clauseelement),
("_fetch_clause", InternalTraversal.dp_clauseelement),
("_fetch_clause_options", InternalTraversal.dp_plain_dict),
("_order_by_clauses", InternalTraversal.dp_clauseelement_list),
("_group_by_clauses", InternalTraversal.dp_clauseelement_list),
("_for_update_arg", InternalTraversal.dp_clauseelement),
("keyword", InternalTraversal.dp_string),
]
+ SupportsCloneAnnotations._clone_annotations_traverse_internals
+ HasCTE._has_ctes_traverse_internals
)
selects: List[SelectBase]
_is_from_container = True
_auto_correlate = False
def __init__(
self,
keyword: _CompoundSelectKeyword,
*selects: _SelectStatementForCompoundArgument,
):
self.keyword = keyword
self.selects = [
coercions.expect(
roles.CompoundElementRole, s, apply_propagate_attrs=self
).self_group(against=self)
for s in selects
]
GenerativeSelect.__init__(self)
@classmethod
def _create_union(
cls, *selects: _SelectStatementForCompoundArgument
) -> CompoundSelect:
return CompoundSelect(_CompoundSelectKeyword.UNION, *selects)
@classmethod
def _create_union_all(
cls, *selects: _SelectStatementForCompoundArgument
) -> CompoundSelect:
return CompoundSelect(_CompoundSelectKeyword.UNION_ALL, *selects)
@classmethod
def _create_except(
cls, *selects: _SelectStatementForCompoundArgument
) -> CompoundSelect:
return CompoundSelect(_CompoundSelectKeyword.EXCEPT, *selects)
@classmethod
def _create_except_all(
cls, *selects: _SelectStatementForCompoundArgument
) -> CompoundSelect:
return CompoundSelect(_CompoundSelectKeyword.EXCEPT_ALL, *selects)
@classmethod
def _create_intersect(
cls, *selects: _SelectStatementForCompoundArgument
) -> CompoundSelect:
return CompoundSelect(_CompoundSelectKeyword.INTERSECT, *selects)
@classmethod
def _create_intersect_all(
cls, *selects: _SelectStatementForCompoundArgument
) -> CompoundSelect:
return CompoundSelect(_CompoundSelectKeyword.INTERSECT_ALL, *selects)
def _scalar_type(self) -> TypeEngine[Any]:
return self.selects[0]._scalar_type()
def self_group(
self, against: Optional[OperatorType] = None
) -> GroupedElement:
return SelectStatementGrouping(self)
def is_derived_from(self, fromclause: Optional[FromClause]) -> bool:
for s in self.selects:
if s.is_derived_from(fromclause):
return True
return False
def set_label_style(self, style: SelectLabelStyle) -> CompoundSelect:
if self._label_style is not style:
self = self._generate()
select_0 = self.selects[0].set_label_style(style)
self.selects = [select_0] + self.selects[1:]
return self
def _ensure_disambiguated_names(self) -> CompoundSelect:
new_select = self.selects[0]._ensure_disambiguated_names()
if new_select is not self.selects[0]:
self = self._generate()
self.selects = [new_select] + self.selects[1:]
return self
def _generate_fromclause_column_proxies(
self,
subquery: FromClause,
*,
proxy_compound_columns: Optional[
Iterable[Sequence[ColumnElement[Any]]]
] = None,
) -> None:
# this is a slightly hacky thing - the union exports a
# column that resembles just that of the *first* selectable.
# to get at a "composite" column, particularly foreign keys,
# you have to dig through the proxies collection which we
# generate below.
select_0 = self.selects[0]
if self._label_style is not LABEL_STYLE_DEFAULT:
select_0 = select_0.set_label_style(self._label_style)
# hand-construct the "_proxies" collection to include all
# derived columns place a 'weight' annotation corresponding
# to how low in the list of select()s the column occurs, so
# that the corresponding_column() operation can resolve
# conflicts
extra_col_iterator = zip(
*[
[
c._annotate(dd)
for c in stmt._all_selected_columns
if is_column_element(c)
]
for dd, stmt in [
({"weight": i + 1}, stmt)
for i, stmt in enumerate(self.selects)
]
]
)
# the incoming proxy_compound_columns can be present also if this is
# a compound embedded in a compound. it's probably more appropriate
# that we generate new weights local to this nested compound, though
# i haven't tried to think what it means for compound nested in
# compound
select_0._generate_fromclause_column_proxies(
subquery, proxy_compound_columns=extra_col_iterator
)
def _refresh_for_new_column(self, column: ColumnElement[Any]) -> None:
super()._refresh_for_new_column(column)
for select in self.selects:
select._refresh_for_new_column(column)
@util.ro_non_memoized_property
def _all_selected_columns(self) -> _SelectIterable:
return self.selects[0]._all_selected_columns
@util.ro_non_memoized_property
def selected_columns(
self,
) -> ColumnCollection[str, ColumnElement[Any]]:
"""A :class:`_expression.ColumnCollection`
representing the columns that
this SELECT statement or similar construct returns in its result set,
not including :class:`_sql.TextClause` constructs.
For a :class:`_expression.CompoundSelect`, the
:attr:`_expression.CompoundSelect.selected_columns`
attribute returns the selected
columns of the first SELECT statement contained within the series of
statements within the set operation.
.. seealso::
:attr:`_sql.Select.selected_columns`
.. versionadded:: 1.4
"""
return self.selects[0].selected_columns
# backwards compat
for elem in _CompoundSelectKeyword:
setattr(CompoundSelect, elem.name, elem)
@CompileState.plugin_for("default", "select")
class SelectState(util.MemoizedSlots, CompileState):
__slots__ = (
"from_clauses",
"froms",
"columns_plus_names",
"_label_resolve_dict",
)
if TYPE_CHECKING:
default_select_compile_options: CacheableOptions
else:
class default_select_compile_options(CacheableOptions):
_cache_key_traversal = []
if TYPE_CHECKING:
@classmethod
def get_plugin_class(
cls, statement: Executable
) -> Type[SelectState]: ...
def __init__(
self,
statement: Select[Any],
compiler: Optional[SQLCompiler],
**kw: Any,
):
self.statement = statement
self.from_clauses = statement._from_obj
for memoized_entities in statement._memoized_select_entities:
self._setup_joins(
memoized_entities._setup_joins, memoized_entities._raw_columns
)
if statement._setup_joins:
self._setup_joins(statement._setup_joins, statement._raw_columns)
self.froms = self._get_froms(statement)
self.columns_plus_names = statement._generate_columns_plus_names(True)
@classmethod
def _plugin_not_implemented(cls) -> NoReturn:
raise NotImplementedError(
"The default SELECT construct without plugins does not "
"implement this method."
)
@classmethod
def get_column_descriptions(
cls, statement: Select[Any]
) -> List[Dict[str, Any]]:
return [
{
"name": name,
"type": element.type,
"expr": element,
}
for _, name, _, element, _ in (
statement._generate_columns_plus_names(False)
)
]
@classmethod
def from_statement(
cls, statement: Select[Any], from_statement: roles.ReturnsRowsRole
) -> ExecutableReturnsRows:
cls._plugin_not_implemented()
@classmethod
def get_columns_clause_froms(
cls, statement: Select[Any]
) -> List[FromClause]:
return cls._normalize_froms(
itertools.chain.from_iterable(
element._from_objects for element in statement._raw_columns
)
)
@classmethod
def _column_naming_convention(
cls, label_style: SelectLabelStyle
) -> _LabelConventionCallable:
table_qualified = label_style is LABEL_STYLE_TABLENAME_PLUS_COL
dedupe = label_style is not LABEL_STYLE_NONE
pa = prefix_anon_map()
names = set()
def go(
c: Union[ColumnElement[Any], TextClause],
col_name: Optional[str] = None,
) -> Optional[str]:
if is_text_clause(c):
return None
elif TYPE_CHECKING:
assert is_column_element(c)
if not dedupe:
name = c._proxy_key
if name is None:
name = "_no_label"
return name
name = c._tq_key_label if table_qualified else c._proxy_key
if name is None:
name = "_no_label"
if name in names:
return c._anon_label(name) % pa
else:
names.add(name)
return name
elif name in names:
return (
c._anon_tq_key_label % pa
if table_qualified
else c._anon_key_label % pa
)
else:
names.add(name)
return name
return go
def _get_froms(self, statement: Select[Any]) -> List[FromClause]:
ambiguous_table_name_map: _AmbiguousTableNameMap
self._ambiguous_table_name_map = ambiguous_table_name_map = {}
return self._normalize_froms(
itertools.chain(
self.from_clauses,
itertools.chain.from_iterable(
[
element._from_objects
for element in statement._raw_columns
]
),
itertools.chain.from_iterable(
[
element._from_objects
for element in statement._where_criteria
]
),
),
check_statement=statement,
ambiguous_table_name_map=ambiguous_table_name_map,
)
@classmethod
def _normalize_froms(
cls,
iterable_of_froms: Iterable[FromClause],
check_statement: Optional[Select[Any]] = None,
ambiguous_table_name_map: Optional[_AmbiguousTableNameMap] = None,
) -> List[FromClause]:
"""given an iterable of things to select FROM, reduce them to what
would actually render in the FROM clause of a SELECT.
This does the job of checking for JOINs, tables, etc. that are in fact
overlapping due to cloning, adaption, present in overlapping joins,
etc.
"""
seen: Set[FromClause] = set()
froms: List[FromClause] = []
for item in iterable_of_froms:
if is_subquery(item) and item.element is check_statement:
raise exc.InvalidRequestError(
"select() construct refers to itself as a FROM"
)
if not seen.intersection(item._cloned_set):
froms.append(item)
seen.update(item._cloned_set)
if froms:
toremove = set(
itertools.chain.from_iterable(
[_expand_cloned(f._hide_froms) for f in froms]
)
)
if toremove:
# filter out to FROM clauses not in the list,
# using a list to maintain ordering
froms = [f for f in froms if f not in toremove]
if ambiguous_table_name_map is not None:
ambiguous_table_name_map.update(
(
fr.name,
_anonymous_label.safe_construct(
hash(fr.name), fr.name
),
)
for item in froms
for fr in item._from_objects
if is_table(fr)
and fr.schema
and fr.name not in ambiguous_table_name_map
)
return froms
def _get_display_froms(
self,
explicit_correlate_froms: Optional[Sequence[FromClause]] = None,
implicit_correlate_froms: Optional[Sequence[FromClause]] = None,
) -> List[FromClause]:
"""Return the full list of 'from' clauses to be displayed.
Takes into account a set of existing froms which may be
rendered in the FROM clause of enclosing selects; this Select
may want to leave those absent if it is automatically
correlating.
"""
froms = self.froms
if self.statement._correlate:
to_correlate = self.statement._correlate
if to_correlate:
froms = [
f
for f in froms
if f
not in _cloned_intersection(
_cloned_intersection(
froms, explicit_correlate_froms or ()
),
to_correlate,
)
]
if self.statement._correlate_except is not None:
froms = [
f
for f in froms
if f
not in _cloned_difference(
_cloned_intersection(
froms, explicit_correlate_froms or ()
),
self.statement._correlate_except,
)
]
if (
self.statement._auto_correlate
and implicit_correlate_froms
and len(froms) > 1
):
froms = [
f
for f in froms
if f
not in _cloned_intersection(froms, implicit_correlate_froms)
]
if not len(froms):
raise exc.InvalidRequestError(
"Select statement '%r"
"' returned no FROM clauses "
"due to auto-correlation; "
"specify correlate(<tables>) "
"to control correlation "
"manually." % self.statement
)
return froms
def _memoized_attr__label_resolve_dict(
self,
) -> Tuple[
Dict[str, ColumnElement[Any]],
Dict[str, ColumnElement[Any]],
Dict[str, ColumnElement[Any]],
]:
with_cols: Dict[str, ColumnElement[Any]] = {
c._tq_label or c.key: c
for c in self.statement._all_selected_columns
if c._allow_label_resolve
}
only_froms: Dict[str, ColumnElement[Any]] = {
c.key: c # type: ignore
for c in _select_iterables(self.froms)
if c._allow_label_resolve
}
only_cols: Dict[str, ColumnElement[Any]] = with_cols.copy()
for key, value in only_froms.items():
with_cols.setdefault(key, value)
return with_cols, only_froms, only_cols
@classmethod
def determine_last_joined_entity(
cls, stmt: Select[Any]
) -> Optional[_JoinTargetElement]:
if stmt._setup_joins:
return stmt._setup_joins[-1][0]
else:
return None
@classmethod
def all_selected_columns(cls, statement: Select[Any]) -> _SelectIterable:
return [c for c in _select_iterables(statement._raw_columns)]
def _setup_joins(
self,
args: Tuple[_SetupJoinsElement, ...],
raw_columns: List[_ColumnsClauseElement],
) -> None:
for right, onclause, left, flags in args:
if TYPE_CHECKING:
if onclause is not None:
assert isinstance(onclause, ColumnElement)
isouter = flags["isouter"]
full = flags["full"]
if left is None:
(
left,
replace_from_obj_index,
) = self._join_determine_implicit_left_side(
raw_columns, left, right, onclause
)
else:
(replace_from_obj_index) = self._join_place_explicit_left_side(
left
)
# these assertions can be made here, as if the right/onclause
# contained ORM elements, the select() statement would have been
# upgraded to an ORM select, and this method would not be called;
# orm.context.ORMSelectCompileState._join() would be
# used instead.
if TYPE_CHECKING:
assert isinstance(right, FromClause)
if onclause is not None:
assert isinstance(onclause, ColumnElement)
if replace_from_obj_index is not None:
# splice into an existing element in the
# self._from_obj list
left_clause = self.from_clauses[replace_from_obj_index]
self.from_clauses = (
self.from_clauses[:replace_from_obj_index]
+ (
Join(
left_clause,
right,
onclause,
isouter=isouter,
full=full,
),
)
+ self.from_clauses[replace_from_obj_index + 1 :]
)
else:
assert left is not None
self.from_clauses = self.from_clauses + (
Join(left, right, onclause, isouter=isouter, full=full),
)
@util.preload_module("sqlalchemy.sql.util")
def _join_determine_implicit_left_side(
self,
raw_columns: List[_ColumnsClauseElement],
left: Optional[FromClause],
right: _JoinTargetElement,
onclause: Optional[ColumnElement[Any]],
) -> Tuple[Optional[FromClause], Optional[int]]:
"""When join conditions don't express the left side explicitly,
determine if an existing FROM or entity in this query
can serve as the left hand side.
"""
sql_util = util.preloaded.sql_util
replace_from_obj_index: Optional[int] = None
from_clauses = self.from_clauses
if from_clauses:
indexes: List[int] = sql_util.find_left_clause_to_join_from(
from_clauses, right, onclause
)
if len(indexes) == 1:
replace_from_obj_index = indexes[0]
left = from_clauses[replace_from_obj_index]
else:
potential = {}
statement = self.statement
for from_clause in itertools.chain(
itertools.chain.from_iterable(
[element._from_objects for element in raw_columns]
),
itertools.chain.from_iterable(
[
element._from_objects
for element in statement._where_criteria
]
),
):
potential[from_clause] = ()
all_clauses = list(potential.keys())
indexes = sql_util.find_left_clause_to_join_from(
all_clauses, right, onclause
)
if len(indexes) == 1:
left = all_clauses[indexes[0]]
if len(indexes) > 1:
raise exc.InvalidRequestError(
"Can't determine which FROM clause to join "
"from, there are multiple FROMS which can "
"join to this entity. Please use the .select_from() "
"method to establish an explicit left side, as well as "
"providing an explicit ON clause if not present already to "
"help resolve the ambiguity."
)
elif not indexes:
raise exc.InvalidRequestError(
"Don't know how to join to %r. "
"Please use the .select_from() "
"method to establish an explicit left side, as well as "
"providing an explicit ON clause if not present already to "
"help resolve the ambiguity." % (right,)
)
return left, replace_from_obj_index
@util.preload_module("sqlalchemy.sql.util")
def _join_place_explicit_left_side(
self, left: FromClause
) -> Optional[int]:
replace_from_obj_index: Optional[int] = None
sql_util = util.preloaded.sql_util
from_clauses = list(self.statement._iterate_from_elements())
if from_clauses:
indexes: List[int] = sql_util.find_left_clause_that_matches_given(
self.from_clauses, left
)
else:
indexes = []
if len(indexes) > 1:
raise exc.InvalidRequestError(
"Can't identify which entity in which to assign the "
"left side of this join. Please use a more specific "
"ON clause."
)
# have an index, means the left side is already present in
# an existing FROM in the self._from_obj tuple
if indexes:
replace_from_obj_index = indexes[0]
# no index, means we need to add a new element to the
# self._from_obj tuple
return replace_from_obj_index
class _SelectFromElements:
__slots__ = ()
_raw_columns: List[_ColumnsClauseElement]
_where_criteria: Tuple[ColumnElement[Any], ...]
_from_obj: Tuple[FromClause, ...]
def _iterate_from_elements(self) -> Iterator[FromClause]:
# note this does not include elements
# in _setup_joins
seen = set()
for element in self._raw_columns:
for fr in element._from_objects:
if fr in seen:
continue
seen.add(fr)
yield fr
for element in self._where_criteria:
for fr in element._from_objects:
if fr in seen:
continue
seen.add(fr)
yield fr
for element in self._from_obj:
if element in seen:
continue
seen.add(element)
yield element
class _MemoizedSelectEntities(
cache_key.HasCacheKey, traversals.HasCopyInternals, visitors.Traversible
):
"""represents partial state from a Select object, for the case
where Select.columns() has redefined the set of columns/entities the
statement will be SELECTing from. This object represents
the entities from the SELECT before that transformation was applied,
so that transformations that were made in terms of the SELECT at that
time, such as join() as well as options(), can access the correct context.
In previous SQLAlchemy versions, this wasn't needed because these
constructs calculated everything up front, like when you called join()
or options(), it did everything to figure out how that would translate
into specific SQL constructs that would be ready to send directly to the
SQL compiler when needed. But as of
1.4, all of that stuff is done in the compilation phase, during the
"compile state" portion of the process, so that the work can all be
cached. So it needs to be able to resolve joins/options2 based on what
the list of entities was when those methods were called.
"""
__visit_name__ = "memoized_select_entities"
_traverse_internals: _TraverseInternalsType = [
("_raw_columns", InternalTraversal.dp_clauseelement_list),
("_setup_joins", InternalTraversal.dp_setup_join_tuple),
("_with_options", InternalTraversal.dp_executable_options),
]
_is_clone_of: Optional[ClauseElement]
_raw_columns: List[_ColumnsClauseElement]
_setup_joins: Tuple[_SetupJoinsElement, ...]
_with_options: Tuple[ExecutableOption, ...]
_annotations = util.EMPTY_DICT
def _clone(self, **kw: Any) -> Self:
c = self.__class__.__new__(self.__class__)
c.__dict__ = {k: v for k, v in self.__dict__.items()}
c._is_clone_of = self.__dict__.get("_is_clone_of", self)
return c
@classmethod
def _generate_for_statement(cls, select_stmt: Select[Any]) -> None:
if select_stmt._setup_joins or select_stmt._with_options:
self = _MemoizedSelectEntities()
self._raw_columns = select_stmt._raw_columns
self._setup_joins = select_stmt._setup_joins
self._with_options = select_stmt._with_options
select_stmt._memoized_select_entities += (self,)
select_stmt._raw_columns = []
select_stmt._setup_joins = select_stmt._with_options = ()
class Select(
HasPrefixes,
HasSuffixes,
HasHints,
HasCompileState,
_SelectFromElements,
GenerativeSelect,
TypedReturnsRows[_TP],
):
"""Represents a ``SELECT`` statement.
The :class:`_sql.Select` object is normally constructed using the
:func:`_sql.select` function. See that function for details.
.. seealso::
:func:`_sql.select`
:ref:`tutorial_selecting_data` - in the 2.0 tutorial
"""
__visit_name__ = "select"
_setup_joins: Tuple[_SetupJoinsElement, ...] = ()
_memoized_select_entities: Tuple[TODO_Any, ...] = ()
_raw_columns: List[_ColumnsClauseElement]
_distinct: bool = False
_distinct_on: Tuple[ColumnElement[Any], ...] = ()
_correlate: Tuple[FromClause, ...] = ()
_correlate_except: Optional[Tuple[FromClause, ...]] = None
_where_criteria: Tuple[ColumnElement[Any], ...] = ()
_having_criteria: Tuple[ColumnElement[Any], ...] = ()
_from_obj: Tuple[FromClause, ...] = ()
_auto_correlate = True
_is_select_statement = True
_compile_options: CacheableOptions = (
SelectState.default_select_compile_options
)
_traverse_internals: _TraverseInternalsType = (
[
("_raw_columns", InternalTraversal.dp_clauseelement_list),
(
"_memoized_select_entities",
InternalTraversal.dp_memoized_select_entities,
),
("_from_obj", InternalTraversal.dp_clauseelement_list),
("_where_criteria", InternalTraversal.dp_clauseelement_tuple),
("_having_criteria", InternalTraversal.dp_clauseelement_tuple),
("_order_by_clauses", InternalTraversal.dp_clauseelement_tuple),
("_group_by_clauses", InternalTraversal.dp_clauseelement_tuple),
("_setup_joins", InternalTraversal.dp_setup_join_tuple),
("_correlate", InternalTraversal.dp_clauseelement_tuple),
("_correlate_except", InternalTraversal.dp_clauseelement_tuple),
("_limit_clause", InternalTraversal.dp_clauseelement),
("_offset_clause", InternalTraversal.dp_clauseelement),
("_fetch_clause", InternalTraversal.dp_clauseelement),
("_fetch_clause_options", InternalTraversal.dp_plain_dict),
("_for_update_arg", InternalTraversal.dp_clauseelement),
("_distinct", InternalTraversal.dp_boolean),
("_distinct_on", InternalTraversal.dp_clauseelement_tuple),
("_label_style", InternalTraversal.dp_plain_obj),
]
+ HasCTE._has_ctes_traverse_internals
+ HasPrefixes._has_prefixes_traverse_internals
+ HasSuffixes._has_suffixes_traverse_internals
+ HasHints._has_hints_traverse_internals
+ SupportsCloneAnnotations._clone_annotations_traverse_internals
+ Executable._executable_traverse_internals
)
_cache_key_traversal: _CacheKeyTraversalType = _traverse_internals + [
("_compile_options", InternalTraversal.dp_has_cache_key)
]
_compile_state_factory: Type[SelectState]
@classmethod
def _create_raw_select(cls, **kw: Any) -> Select[Any]:
"""Create a :class:`.Select` using raw ``__new__`` with no coercions.
Used internally to build up :class:`.Select` constructs with
pre-established state.
"""
stmt = Select.__new__(Select)
stmt.__dict__.update(kw)
return stmt
def __init__(self, *entities: _ColumnsClauseArgument[Any]):
r"""Construct a new :class:`_expression.Select`.
The public constructor for :class:`_expression.Select` is the
:func:`_sql.select` function.
"""
self._raw_columns = [
coercions.expect(
roles.ColumnsClauseRole, ent, apply_propagate_attrs=self
)
for ent in entities
]
GenerativeSelect.__init__(self)
def _scalar_type(self) -> TypeEngine[Any]:
if not self._raw_columns:
return NULLTYPE
elem = self._raw_columns[0]
cols = list(elem._select_iterable)
return cols[0].type
def filter(self, *criteria: _ColumnExpressionArgument[bool]) -> Self:
"""A synonym for the :meth:`_sql.Select.where` method."""
return self.where(*criteria)
def _filter_by_zero(
self,
) -> Union[
FromClause, _JoinTargetProtocol, ColumnElement[Any], TextClause
]:
if self._setup_joins:
meth = SelectState.get_plugin_class(
self
).determine_last_joined_entity
_last_joined_entity = meth(self)
if _last_joined_entity is not None:
return _last_joined_entity
if self._from_obj:
return self._from_obj[0]
return self._raw_columns[0]
if TYPE_CHECKING:
@overload
def scalar_subquery(
self: Select[Tuple[_MAYBE_ENTITY]],
) -> ScalarSelect[Any]: ...
@overload
def scalar_subquery(
self: Select[Tuple[_NOT_ENTITY]],
) -> ScalarSelect[_NOT_ENTITY]: ...
@overload
def scalar_subquery(self) -> ScalarSelect[Any]: ...
def scalar_subquery(self) -> ScalarSelect[Any]: ...
def filter_by(self, **kwargs: Any) -> Self:
r"""apply the given filtering criterion as a WHERE clause
to this select.
"""
from_entity = self._filter_by_zero()
clauses = [
_entity_namespace_key(from_entity, key) == value
for key, value in kwargs.items()
]
return self.filter(*clauses)
@property
def column_descriptions(self) -> Any:
"""Return a :term:`plugin-enabled` 'column descriptions' structure
referring to the columns which are SELECTed by this statement.
This attribute is generally useful when using the ORM, as an
extended structure which includes information about mapped
entities is returned. The section :ref:`queryguide_inspection`
contains more background.
For a Core-only statement, the structure returned by this accessor
is derived from the same objects that are returned by the
:attr:`.Select.selected_columns` accessor, formatted as a list of
dictionaries which contain the keys ``name``, ``type`` and ``expr``,
which indicate the column expressions to be selected::
>>> stmt = select(user_table)
>>> stmt.column_descriptions
[
{
'name': 'id',
'type': Integer(),
'expr': Column('id', Integer(), ...)},
{
'name': 'name',
'type': String(length=30),
'expr': Column('name', String(length=30), ...)}
]
.. versionchanged:: 1.4.33 The :attr:`.Select.column_descriptions`
attribute returns a structure for a Core-only set of entities,
not just ORM-only entities.
.. seealso::
:attr:`.UpdateBase.entity_description` - entity information for
an :func:`.insert`, :func:`.update`, or :func:`.delete`
:ref:`queryguide_inspection` - ORM background
"""
meth = SelectState.get_plugin_class(self).get_column_descriptions
return meth(self)
def from_statement(
self, statement: roles.ReturnsRowsRole
) -> ExecutableReturnsRows:
"""Apply the columns which this :class:`.Select` would select
onto another statement.
This operation is :term:`plugin-specific` and will raise a not
supported exception if this :class:`_sql.Select` does not select from
plugin-enabled entities.
The statement is typically either a :func:`_expression.text` or
:func:`_expression.select` construct, and should return the set of
columns appropriate to the entities represented by this
:class:`.Select`.
.. seealso::
:ref:`orm_queryguide_selecting_text` - usage examples in the
ORM Querying Guide
"""
meth = SelectState.get_plugin_class(self).from_statement
return meth(self, statement)
@_generative
def join(
self,
target: _JoinTargetArgument,
onclause: Optional[_OnClauseArgument] = None,
*,
isouter: bool = False,
full: bool = False,
) -> Self:
r"""Create a SQL JOIN against this :class:`_expression.Select`
object's criterion
and apply generatively, returning the newly resulting
:class:`_expression.Select`.
E.g.::
stmt = select(user_table).join(address_table, user_table.c.id == address_table.c.user_id)
The above statement generates SQL similar to::
SELECT user.id, user.name FROM user JOIN address ON user.id = address.user_id
.. versionchanged:: 1.4 :meth:`_expression.Select.join` now creates
a :class:`_sql.Join` object between a :class:`_sql.FromClause`
source that is within the FROM clause of the existing SELECT,
and a given target :class:`_sql.FromClause`, and then adds
this :class:`_sql.Join` to the FROM clause of the newly generated
SELECT statement. This is completely reworked from the behavior
in 1.3, which would instead create a subquery of the entire
:class:`_expression.Select` and then join that subquery to the
target.
This is a **backwards incompatible change** as the previous behavior
was mostly useless, producing an unnamed subquery rejected by
most databases in any case. The new behavior is modeled after
that of the very successful :meth:`_orm.Query.join` method in the
ORM, in order to support the functionality of :class:`_orm.Query`
being available by using a :class:`_sql.Select` object with an
:class:`_orm.Session`.
See the notes for this change at :ref:`change_select_join`.
:param target: target table to join towards
:param onclause: ON clause of the join. If omitted, an ON clause
is generated automatically based on the :class:`_schema.ForeignKey`
linkages between the two tables, if one can be unambiguously
determined, otherwise an error is raised.
:param isouter: if True, generate LEFT OUTER join. Same as
:meth:`_expression.Select.outerjoin`.
:param full: if True, generate FULL OUTER join.
.. seealso::
:ref:`tutorial_select_join` - in the :doc:`/tutorial/index`
:ref:`orm_queryguide_joins` - in the :ref:`queryguide_toplevel`
:meth:`_expression.Select.join_from`
:meth:`_expression.Select.outerjoin`
""" # noqa: E501
join_target = coercions.expect(
roles.JoinTargetRole, target, apply_propagate_attrs=self
)
if onclause is not None:
onclause_element = coercions.expect(roles.OnClauseRole, onclause)
else:
onclause_element = None
self._setup_joins += (
(
join_target,
onclause_element,
None,
{"isouter": isouter, "full": full},
),
)
return self
def outerjoin_from(
self,
from_: _FromClauseArgument,
target: _JoinTargetArgument,
onclause: Optional[_OnClauseArgument] = None,
*,
full: bool = False,
) -> Self:
r"""Create a SQL LEFT OUTER JOIN against this
:class:`_expression.Select` object's criterion and apply generatively,
returning the newly resulting :class:`_expression.Select`.
Usage is the same as that of :meth:`_selectable.Select.join_from`.
"""
return self.join_from(
from_, target, onclause=onclause, isouter=True, full=full
)
@_generative
def join_from(
self,
from_: _FromClauseArgument,
target: _JoinTargetArgument,
onclause: Optional[_OnClauseArgument] = None,
*,
isouter: bool = False,
full: bool = False,
) -> Self:
r"""Create a SQL JOIN against this :class:`_expression.Select`
object's criterion
and apply generatively, returning the newly resulting
:class:`_expression.Select`.
E.g.::
stmt = select(user_table, address_table).join_from(
user_table, address_table, user_table.c.id == address_table.c.user_id
)
The above statement generates SQL similar to::
SELECT user.id, user.name, address.id, address.email, address.user_id
FROM user JOIN address ON user.id = address.user_id
.. versionadded:: 1.4
:param from\_: the left side of the join, will be rendered in the
FROM clause and is roughly equivalent to using the
:meth:`.Select.select_from` method.
:param target: target table to join towards
:param onclause: ON clause of the join.
:param isouter: if True, generate LEFT OUTER join. Same as
:meth:`_expression.Select.outerjoin`.
:param full: if True, generate FULL OUTER join.
.. seealso::
:ref:`tutorial_select_join` - in the :doc:`/tutorial/index`
:ref:`orm_queryguide_joins` - in the :ref:`queryguide_toplevel`
:meth:`_expression.Select.join`
""" # noqa: E501
# note the order of parsing from vs. target is important here, as we
# are also deriving the source of the plugin (i.e. the subject mapper
# in an ORM query) which should favor the "from_" over the "target"
from_ = coercions.expect(
roles.FromClauseRole, from_, apply_propagate_attrs=self
)
join_target = coercions.expect(
roles.JoinTargetRole, target, apply_propagate_attrs=self
)
if onclause is not None:
onclause_element = coercions.expect(roles.OnClauseRole, onclause)
else:
onclause_element = None
self._setup_joins += (
(
join_target,
onclause_element,
from_,
{"isouter": isouter, "full": full},
),
)
return self
def outerjoin(
self,
target: _JoinTargetArgument,
onclause: Optional[_OnClauseArgument] = None,
*,
full: bool = False,
) -> Self:
"""Create a left outer join.
Parameters are the same as that of :meth:`_expression.Select.join`.
.. versionchanged:: 1.4 :meth:`_expression.Select.outerjoin` now
creates a :class:`_sql.Join` object between a
:class:`_sql.FromClause` source that is within the FROM clause of
the existing SELECT, and a given target :class:`_sql.FromClause`,
and then adds this :class:`_sql.Join` to the FROM clause of the
newly generated SELECT statement. This is completely reworked
from the behavior in 1.3, which would instead create a subquery of
the entire
:class:`_expression.Select` and then join that subquery to the
target.
This is a **backwards incompatible change** as the previous behavior
was mostly useless, producing an unnamed subquery rejected by
most databases in any case. The new behavior is modeled after
that of the very successful :meth:`_orm.Query.join` method in the
ORM, in order to support the functionality of :class:`_orm.Query`
being available by using a :class:`_sql.Select` object with an
:class:`_orm.Session`.
See the notes for this change at :ref:`change_select_join`.
.. seealso::
:ref:`tutorial_select_join` - in the :doc:`/tutorial/index`
:ref:`orm_queryguide_joins` - in the :ref:`queryguide_toplevel`
:meth:`_expression.Select.join`
"""
return self.join(target, onclause=onclause, isouter=True, full=full)
def get_final_froms(self) -> Sequence[FromClause]:
"""Compute the final displayed list of :class:`_expression.FromClause`
elements.
This method will run through the full computation required to
determine what FROM elements will be displayed in the resulting
SELECT statement, including shadowing individual tables with
JOIN objects, as well as full computation for ORM use cases including
eager loading clauses.
For ORM use, this accessor returns the **post compilation**
list of FROM objects; this collection will include elements such as
eagerly loaded tables and joins. The objects will **not** be
ORM enabled and not work as a replacement for the
:meth:`_sql.Select.select_froms` collection; additionally, the
method is not well performing for an ORM enabled statement as it
will incur the full ORM construction process.
To retrieve the FROM list that's implied by the "columns" collection
passed to the :class:`_sql.Select` originally, use the
:attr:`_sql.Select.columns_clause_froms` accessor.
To select from an alternative set of columns while maintaining the
FROM list, use the :meth:`_sql.Select.with_only_columns` method and
pass the
:paramref:`_sql.Select.with_only_columns.maintain_column_froms`
parameter.
.. versionadded:: 1.4.23 - the :meth:`_sql.Select.get_final_froms`
method replaces the previous :attr:`_sql.Select.froms` accessor,
which is deprecated.
.. seealso::
:attr:`_sql.Select.columns_clause_froms`
"""
return self._compile_state_factory(self, None)._get_display_froms()
@property
@util.deprecated(
"1.4.23",
"The :attr:`_expression.Select.froms` attribute is moved to "
"the :meth:`_expression.Select.get_final_froms` method.",
)
def froms(self) -> Sequence[FromClause]:
"""Return the displayed list of :class:`_expression.FromClause`
elements.
"""
return self.get_final_froms()
@property
def columns_clause_froms(self) -> List[FromClause]:
"""Return the set of :class:`_expression.FromClause` objects implied
by the columns clause of this SELECT statement.
.. versionadded:: 1.4.23
.. seealso::
:attr:`_sql.Select.froms` - "final" FROM list taking the full
statement into account
:meth:`_sql.Select.with_only_columns` - makes use of this
collection to set up a new FROM list
"""
return SelectState.get_plugin_class(self).get_columns_clause_froms(
self
)
@property
def inner_columns(self) -> _SelectIterable:
"""An iterator of all :class:`_expression.ColumnElement`
expressions which would
be rendered into the columns clause of the resulting SELECT statement.
This method is legacy as of 1.4 and is superseded by the
:attr:`_expression.Select.exported_columns` collection.
"""
return iter(self._all_selected_columns)
def is_derived_from(self, fromclause: Optional[FromClause]) -> bool:
if fromclause is not None and self in fromclause._cloned_set:
return True
for f in self._iterate_from_elements():
if f.is_derived_from(fromclause):
return True
return False
def _copy_internals(
self, clone: _CloneCallableType = _clone, **kw: Any
) -> None:
# Select() object has been cloned and probably adapted by the
# given clone function. Apply the cloning function to internal
# objects
# 1. keep a dictionary of the froms we've cloned, and what
# they've become. This allows us to ensure the same cloned from
# is used when other items such as columns are "cloned"
all_the_froms = set(
itertools.chain(
_from_objects(*self._raw_columns),
_from_objects(*self._where_criteria),
_from_objects(*[elem[0] for elem in self._setup_joins]),
)
)
# do a clone for the froms we've gathered. what is important here
# is if any of the things we are selecting from, like tables,
# were converted into Join objects. if so, these need to be
# added to _from_obj explicitly, because otherwise they won't be
# part of the new state, as they don't associate themselves with
# their columns.
new_froms = {f: clone(f, **kw) for f in all_the_froms}
# 2. copy FROM collections, adding in joins that we've created.
existing_from_obj = [clone(f, **kw) for f in self._from_obj]
add_froms = (
{f for f in new_froms.values() if isinstance(f, Join)}
.difference(all_the_froms)
.difference(existing_from_obj)
)
self._from_obj = tuple(existing_from_obj) + tuple(add_froms)
# 3. clone everything else, making sure we use columns
# corresponding to the froms we just made.
def replace(
obj: Union[BinaryExpression[Any], ColumnClause[Any]],
**kw: Any,
) -> Optional[KeyedColumnElement[ColumnElement[Any]]]:
if isinstance(obj, ColumnClause) and obj.table in new_froms:
newelem = new_froms[obj.table].corresponding_column(obj)
return newelem
return None
kw["replace"] = replace
# copy everything else. for table-ish things like correlate,
# correlate_except, setup_joins, these clone normally. For
# column-expression oriented things like raw_columns, where_criteria,
# order by, we get this from the new froms.
super()._copy_internals(clone=clone, omit_attrs=("_from_obj",), **kw)
self._reset_memoizations()
def get_children(self, **kw: Any) -> Iterable[ClauseElement]:
return itertools.chain(
super().get_children(
omit_attrs=("_from_obj", "_correlate", "_correlate_except"),
**kw,
),
self._iterate_from_elements(),
)
@_generative
def add_columns(
self, *entities: _ColumnsClauseArgument[Any]
) -> Select[Any]:
r"""Return a new :func:`_expression.select` construct with
the given entities appended to its columns clause.
E.g.::
my_select = my_select.add_columns(table.c.new_column)
The original expressions in the columns clause remain in place.
To replace the original expressions with new ones, see the method
:meth:`_expression.Select.with_only_columns`.
:param \*entities: column, table, or other entity expressions to be
added to the columns clause
.. seealso::
:meth:`_expression.Select.with_only_columns` - replaces existing
expressions rather than appending.
:ref:`orm_queryguide_select_multiple_entities` - ORM-centric
example
"""
self._reset_memoizations()
self._raw_columns = self._raw_columns + [
coercions.expect(
roles.ColumnsClauseRole, column, apply_propagate_attrs=self
)
for column in entities
]
return self
def _set_entities(
self, entities: Iterable[_ColumnsClauseArgument[Any]]
) -> None:
self._raw_columns = [
coercions.expect(
roles.ColumnsClauseRole, ent, apply_propagate_attrs=self
)
for ent in util.to_list(entities)
]
@util.deprecated(
"1.4",
"The :meth:`_expression.Select.column` method is deprecated and will "
"be removed in a future release. Please use "
":meth:`_expression.Select.add_columns`",
)
def column(self, column: _ColumnsClauseArgument[Any]) -> Select[Any]:
"""Return a new :func:`_expression.select` construct with
the given column expression added to its columns clause.
E.g.::
my_select = my_select.column(table.c.new_column)
See the documentation for
:meth:`_expression.Select.with_only_columns`
for guidelines on adding /replacing the columns of a
:class:`_expression.Select` object.
"""
return self.add_columns(column)
@util.preload_module("sqlalchemy.sql.util")
def reduce_columns(self, only_synonyms: bool = True) -> Select[Any]:
"""Return a new :func:`_expression.select` construct with redundantly
named, equivalently-valued columns removed from the columns clause.
"Redundant" here means two columns where one refers to the
other either based on foreign key, or via a simple equality
comparison in the WHERE clause of the statement. The primary purpose
of this method is to automatically construct a select statement
with all uniquely-named columns, without the need to use
table-qualified labels as
:meth:`_expression.Select.set_label_style`
does.
When columns are omitted based on foreign key, the referred-to
column is the one that's kept. When columns are omitted based on
WHERE equivalence, the first column in the columns clause is the
one that's kept.
:param only_synonyms: when True, limit the removal of columns
to those which have the same name as the equivalent. Otherwise,
all columns that are equivalent to another are removed.
"""
woc: Select[Any]
woc = self.with_only_columns(
*util.preloaded.sql_util.reduce_columns(
self._all_selected_columns,
only_synonyms=only_synonyms,
*(self._where_criteria + self._from_obj),
)
)
return woc
# START OVERLOADED FUNCTIONS self.with_only_columns Select 8
# code within this block is **programmatically,
# statically generated** by tools/generate_sel_v1_overloads.py
@overload
def with_only_columns(self, __ent0: _TCCA[_T0]) -> Select[Tuple[_T0]]: ...
@overload
def with_only_columns(
self, __ent0: _TCCA[_T0], __ent1: _TCCA[_T1]
) -> Select[Tuple[_T0, _T1]]: ...
@overload
def with_only_columns(
self, __ent0: _TCCA[_T0], __ent1: _TCCA[_T1], __ent2: _TCCA[_T2]
) -> Select[Tuple[_T0, _T1, _T2]]: ...
@overload
def with_only_columns(
self,
__ent0: _TCCA[_T0],
__ent1: _TCCA[_T1],
__ent2: _TCCA[_T2],
__ent3: _TCCA[_T3],
) -> Select[Tuple[_T0, _T1, _T2, _T3]]: ...
@overload
def with_only_columns(
self,
__ent0: _TCCA[_T0],
__ent1: _TCCA[_T1],
__ent2: _TCCA[_T2],
__ent3: _TCCA[_T3],
__ent4: _TCCA[_T4],
) -> Select[Tuple[_T0, _T1, _T2, _T3, _T4]]: ...
@overload
def with_only_columns(
self,
__ent0: _TCCA[_T0],
__ent1: _TCCA[_T1],
__ent2: _TCCA[_T2],
__ent3: _TCCA[_T3],
__ent4: _TCCA[_T4],
__ent5: _TCCA[_T5],
) -> Select[Tuple[_T0, _T1, _T2, _T3, _T4, _T5]]: ...
@overload
def with_only_columns(
self,
__ent0: _TCCA[_T0],
__ent1: _TCCA[_T1],
__ent2: _TCCA[_T2],
__ent3: _TCCA[_T3],
__ent4: _TCCA[_T4],
__ent5: _TCCA[_T5],
__ent6: _TCCA[_T6],
) -> Select[Tuple[_T0, _T1, _T2, _T3, _T4, _T5, _T6]]: ...
@overload
def with_only_columns(
self,
__ent0: _TCCA[_T0],
__ent1: _TCCA[_T1],
__ent2: _TCCA[_T2],
__ent3: _TCCA[_T3],
__ent4: _TCCA[_T4],
__ent5: _TCCA[_T5],
__ent6: _TCCA[_T6],
__ent7: _TCCA[_T7],
) -> Select[Tuple[_T0, _T1, _T2, _T3, _T4, _T5, _T6, _T7]]: ...
# END OVERLOADED FUNCTIONS self.with_only_columns
@overload
def with_only_columns(
self,
*entities: _ColumnsClauseArgument[Any],
maintain_column_froms: bool = False,
**__kw: Any,
) -> Select[Any]: ...
@_generative
def with_only_columns(
self,
*entities: _ColumnsClauseArgument[Any],
maintain_column_froms: bool = False,
**__kw: Any,
) -> Select[Any]:
r"""Return a new :func:`_expression.select` construct with its columns
clause replaced with the given entities.
By default, this method is exactly equivalent to as if the original
:func:`_expression.select` had been called with the given entities.
E.g. a statement::
s = select(table1.c.a, table1.c.b)
s = s.with_only_columns(table1.c.b)
should be exactly equivalent to::
s = select(table1.c.b)
In this mode of operation, :meth:`_sql.Select.with_only_columns`
will also dynamically alter the FROM clause of the
statement if it is not explicitly stated.
To maintain the existing set of FROMs including those implied by the
current columns clause, add the
:paramref:`_sql.Select.with_only_columns.maintain_column_froms`
parameter::
s = select(table1.c.a, table2.c.b)
s = s.with_only_columns(table1.c.a, maintain_column_froms=True)
The above parameter performs a transfer of the effective FROMs
in the columns collection to the :meth:`_sql.Select.select_from`
method, as though the following were invoked::
s = select(table1.c.a, table2.c.b)
s = s.select_from(table1, table2).with_only_columns(table1.c.a)
The :paramref:`_sql.Select.with_only_columns.maintain_column_froms`
parameter makes use of the :attr:`_sql.Select.columns_clause_froms`
collection and performs an operation equivalent to the following::
s = select(table1.c.a, table2.c.b)
s = s.select_from(*s.columns_clause_froms).with_only_columns(table1.c.a)
:param \*entities: column expressions to be used.
:param maintain_column_froms: boolean parameter that will ensure the
FROM list implied from the current columns clause will be transferred
to the :meth:`_sql.Select.select_from` method first.
.. versionadded:: 1.4.23
""" # noqa: E501
if __kw:
raise _no_kw()
# memoizations should be cleared here as of
# I95c560ffcbfa30b26644999412fb6a385125f663 , asserting this
# is the case for now.
self._assert_no_memoizations()
if maintain_column_froms:
self.select_from.non_generative( # type: ignore
self, *self.columns_clause_froms
)
# then memoize the FROMs etc.
_MemoizedSelectEntities._generate_for_statement(self)
self._raw_columns = [
coercions.expect(roles.ColumnsClauseRole, c)
for c in coercions._expression_collection_was_a_list(
"entities", "Select.with_only_columns", entities
)
]
return self
@property
def whereclause(self) -> Optional[ColumnElement[Any]]:
"""Return the completed WHERE clause for this
:class:`_expression.Select` statement.
This assembles the current collection of WHERE criteria
into a single :class:`_expression.BooleanClauseList` construct.
.. versionadded:: 1.4
"""
return BooleanClauseList._construct_for_whereclause(
self._where_criteria
)
_whereclause = whereclause
@_generative
def where(self, *whereclause: _ColumnExpressionArgument[bool]) -> Self:
"""Return a new :func:`_expression.select` construct with
the given expression added to
its WHERE clause, joined to the existing clause via AND, if any.
"""
assert isinstance(self._where_criteria, tuple)
for criterion in whereclause:
where_criteria: ColumnElement[Any] = coercions.expect(
roles.WhereHavingRole, criterion, apply_propagate_attrs=self
)
self._where_criteria += (where_criteria,)
return self
@_generative
def having(self, *having: _ColumnExpressionArgument[bool]) -> Self:
"""Return a new :func:`_expression.select` construct with
the given expression added to
its HAVING clause, joined to the existing clause via AND, if any.
"""
for criterion in having:
having_criteria = coercions.expect(
roles.WhereHavingRole, criterion, apply_propagate_attrs=self
)
self._having_criteria += (having_criteria,)
return self
@_generative
def distinct(self, *expr: _ColumnExpressionArgument[Any]) -> Self:
r"""Return a new :func:`_expression.select` construct which
will apply DISTINCT to the SELECT statement overall.
E.g.::
from sqlalchemy import select
stmt = select(users_table.c.id, users_table.c.name).distinct()
The above would produce an statement resembling::
SELECT DISTINCT user.id, user.name FROM user
The method also accepts an ``*expr`` parameter which produces the
PostgreSQL dialect-specific ``DISTINCT ON`` expression. Using this
parameter on other backends which don't support this syntax will
raise an error.
:param \*expr: optional column expressions. When present,
the PostgreSQL dialect will render a ``DISTINCT ON (<expressions>)``
construct. A deprecation warning and/or :class:`_exc.CompileError`
will be raised on other backends.
.. deprecated:: 1.4 Using \*expr in other dialects is deprecated
and will raise :class:`_exc.CompileError` in a future version.
"""
if expr:
self._distinct = True
self._distinct_on = self._distinct_on + tuple(
coercions.expect(roles.ByOfRole, e, apply_propagate_attrs=self)
for e in expr
)
else:
self._distinct = True
return self
@_generative
def select_from(self, *froms: _FromClauseArgument) -> Self:
r"""Return a new :func:`_expression.select` construct with the
given FROM expression(s)
merged into its list of FROM objects.
E.g.::
table1 = table('t1', column('a'))
table2 = table('t2', column('b'))
s = select(table1.c.a).\
select_from(
table1.join(table2, table1.c.a==table2.c.b)
)
The "from" list is a unique set on the identity of each element,
so adding an already present :class:`_schema.Table`
or other selectable
will have no effect. Passing a :class:`_expression.Join` that refers
to an already present :class:`_schema.Table`
or other selectable will have
the effect of concealing the presence of that selectable as
an individual element in the rendered FROM list, instead
rendering it into a JOIN clause.
While the typical purpose of :meth:`_expression.Select.select_from`
is to
replace the default, derived FROM clause with a join, it can
also be called with individual table elements, multiple times
if desired, in the case that the FROM clause cannot be fully
derived from the columns clause::
select(func.count('*')).select_from(table1)
"""
self._from_obj += tuple(
coercions.expect(
roles.FromClauseRole, fromclause, apply_propagate_attrs=self
)
for fromclause in froms
)
return self
@_generative
def correlate(
self,
*fromclauses: Union[Literal[None, False], _FromClauseArgument],
) -> Self:
r"""Return a new :class:`_expression.Select`
which will correlate the given FROM
clauses to that of an enclosing :class:`_expression.Select`.
Calling this method turns off the :class:`_expression.Select` object's
default behavior of "auto-correlation". Normally, FROM elements
which appear in a :class:`_expression.Select`
that encloses this one via
its :term:`WHERE clause`, ORDER BY, HAVING or
:term:`columns clause` will be omitted from this
:class:`_expression.Select`
object's :term:`FROM clause`.
Setting an explicit correlation collection using the
:meth:`_expression.Select.correlate`
method provides a fixed list of FROM objects
that can potentially take place in this process.
When :meth:`_expression.Select.correlate`
is used to apply specific FROM clauses
for correlation, the FROM elements become candidates for
correlation regardless of how deeply nested this
:class:`_expression.Select`
object is, relative to an enclosing :class:`_expression.Select`
which refers to
the same FROM object. This is in contrast to the behavior of
"auto-correlation" which only correlates to an immediate enclosing
:class:`_expression.Select`.
Multi-level correlation ensures that the link
between enclosed and enclosing :class:`_expression.Select`
is always via
at least one WHERE/ORDER BY/HAVING/columns clause in order for
correlation to take place.
If ``None`` is passed, the :class:`_expression.Select`
object will correlate
none of its FROM entries, and all will render unconditionally
in the local FROM clause.
:param \*fromclauses: one or more :class:`.FromClause` or other
FROM-compatible construct such as an ORM mapped entity to become part
of the correlate collection; alternatively pass a single value
``None`` to remove all existing correlations.
.. seealso::
:meth:`_expression.Select.correlate_except`
:ref:`tutorial_scalar_subquery`
"""
# tests failing when we try to change how these
# arguments are passed
self._auto_correlate = False
if not fromclauses or fromclauses[0] in {None, False}:
if len(fromclauses) > 1:
raise exc.ArgumentError(
"additional FROM objects not accepted when "
"passing None/False to correlate()"
)
self._correlate = ()
else:
self._correlate = self._correlate + tuple(
coercions.expect(roles.FromClauseRole, f) for f in fromclauses
)
return self
@_generative
def correlate_except(
self,
*fromclauses: Union[Literal[None, False], _FromClauseArgument],
) -> Self:
r"""Return a new :class:`_expression.Select`
which will omit the given FROM
clauses from the auto-correlation process.
Calling :meth:`_expression.Select.correlate_except` turns off the
:class:`_expression.Select` object's default behavior of
"auto-correlation" for the given FROM elements. An element
specified here will unconditionally appear in the FROM list, while
all other FROM elements remain subject to normal auto-correlation
behaviors.
If ``None`` is passed, or no arguments are passed,
the :class:`_expression.Select` object will correlate all of its
FROM entries.
:param \*fromclauses: a list of one or more
:class:`_expression.FromClause`
constructs, or other compatible constructs (i.e. ORM-mapped
classes) to become part of the correlate-exception collection.
.. seealso::
:meth:`_expression.Select.correlate`
:ref:`tutorial_scalar_subquery`
"""
self._auto_correlate = False
if not fromclauses or fromclauses[0] in {None, False}:
if len(fromclauses) > 1:
raise exc.ArgumentError(
"additional FROM objects not accepted when "
"passing None/False to correlate_except()"
)
self._correlate_except = ()
else:
self._correlate_except = (self._correlate_except or ()) + tuple(
coercions.expect(roles.FromClauseRole, f) for f in fromclauses
)
return self
@HasMemoized_ro_memoized_attribute
def selected_columns(
self,
) -> ColumnCollection[str, ColumnElement[Any]]:
"""A :class:`_expression.ColumnCollection`
representing the columns that
this SELECT statement or similar construct returns in its result set,
not including :class:`_sql.TextClause` constructs.
This collection differs from the :attr:`_expression.FromClause.columns`
collection of a :class:`_expression.FromClause` in that the columns
within this collection cannot be directly nested inside another SELECT
statement; a subquery must be applied first which provides for the
necessary parenthesization required by SQL.
For a :func:`_expression.select` construct, the collection here is
exactly what would be rendered inside the "SELECT" statement, and the
:class:`_expression.ColumnElement` objects are directly present as they
were given, e.g.::
col1 = column('q', Integer)
col2 = column('p', Integer)
stmt = select(col1, col2)
Above, ``stmt.selected_columns`` would be a collection that contains
the ``col1`` and ``col2`` objects directly. For a statement that is
against a :class:`_schema.Table` or other
:class:`_expression.FromClause`, the collection will use the
:class:`_expression.ColumnElement` objects that are in the
:attr:`_expression.FromClause.c` collection of the from element.
A use case for the :attr:`_sql.Select.selected_columns` collection is
to allow the existing columns to be referenced when adding additional
criteria, e.g.::
def filter_on_id(my_select, id):
return my_select.where(my_select.selected_columns['id'] == id)
stmt = select(MyModel)
# adds "WHERE id=:param" to the statement
stmt = filter_on_id(stmt, 42)
.. note::
The :attr:`_sql.Select.selected_columns` collection does not
include expressions established in the columns clause using the
:func:`_sql.text` construct; these are silently omitted from the
collection. To use plain textual column expressions inside of a
:class:`_sql.Select` construct, use the :func:`_sql.literal_column`
construct.
.. versionadded:: 1.4
"""
# compare to SelectState._generate_columns_plus_names, which
# generates the actual names used in the SELECT string. that
# method is more complex because it also renders columns that are
# fully ambiguous, e.g. same column more than once.
conv = cast(
"Callable[[Any], str]",
SelectState._column_naming_convention(self._label_style),
)
cc: ColumnCollection[str, ColumnElement[Any]] = ColumnCollection(
[
(conv(c), c)
for c in self._all_selected_columns
if is_column_element(c)
]
)
return cc.as_readonly()
@HasMemoized_ro_memoized_attribute
def _all_selected_columns(self) -> _SelectIterable:
meth = SelectState.get_plugin_class(self).all_selected_columns
return list(meth(self))
def _ensure_disambiguated_names(self) -> Select[Any]:
if self._label_style is LABEL_STYLE_NONE:
self = self.set_label_style(LABEL_STYLE_DISAMBIGUATE_ONLY)
return self
def _generate_fromclause_column_proxies(
self,
subquery: FromClause,
*,
proxy_compound_columns: Optional[
Iterable[Sequence[ColumnElement[Any]]]
] = None,
) -> None:
"""Generate column proxies to place in the exported ``.c``
collection of a subquery."""
if proxy_compound_columns:
extra_col_iterator = proxy_compound_columns
prox = [
c._make_proxy(
subquery,
key=proxy_key,
name=required_label_name,
name_is_truncatable=True,
compound_select_cols=extra_cols,
)
for (
(
required_label_name,
proxy_key,
fallback_label_name,
c,
repeated,
),
extra_cols,
) in (
zip(
self._generate_columns_plus_names(False),
extra_col_iterator,
)
)
if is_column_element(c)
]
else:
prox = [
c._make_proxy(
subquery,
key=proxy_key,
name=required_label_name,
name_is_truncatable=True,
)
for (
required_label_name,
proxy_key,
fallback_label_name,
c,
repeated,
) in (self._generate_columns_plus_names(False))
if is_column_element(c)
]
subquery._columns._populate_separate_keys(prox)
def _needs_parens_for_grouping(self) -> bool:
return self._has_row_limiting_clause or bool(
self._order_by_clause.clauses
)
def self_group(
self, against: Optional[OperatorType] = None
) -> Union[SelectStatementGrouping[Self], Self]:
"""Return a 'grouping' construct as per the
:class:`_expression.ClauseElement` specification.
This produces an element that can be embedded in an expression. Note
that this method is called automatically as needed when constructing
expressions and should not require explicit use.
"""
if (
isinstance(against, CompoundSelect)
and not self._needs_parens_for_grouping()
):
return self
else:
return SelectStatementGrouping(self)
def union(
self, *other: _SelectStatementForCompoundArgument
) -> CompoundSelect:
r"""Return a SQL ``UNION`` of this select() construct against
the given selectables provided as positional arguments.
:param \*other: one or more elements with which to create a
UNION.
.. versionchanged:: 1.4.28
multiple elements are now accepted.
:param \**kwargs: keyword arguments are forwarded to the constructor
for the newly created :class:`_sql.CompoundSelect` object.
"""
return CompoundSelect._create_union(self, *other)
def union_all(
self, *other: _SelectStatementForCompoundArgument
) -> CompoundSelect:
r"""Return a SQL ``UNION ALL`` of this select() construct against
the given selectables provided as positional arguments.
:param \*other: one or more elements with which to create a
UNION.
.. versionchanged:: 1.4.28
multiple elements are now accepted.
:param \**kwargs: keyword arguments are forwarded to the constructor
for the newly created :class:`_sql.CompoundSelect` object.
"""
return CompoundSelect._create_union_all(self, *other)
def except_(
self, *other: _SelectStatementForCompoundArgument
) -> CompoundSelect:
r"""Return a SQL ``EXCEPT`` of this select() construct against
the given selectable provided as positional arguments.
:param \*other: one or more elements with which to create a
UNION.
.. versionchanged:: 1.4.28
multiple elements are now accepted.
"""
return CompoundSelect._create_except(self, *other)
def except_all(
self, *other: _SelectStatementForCompoundArgument
) -> CompoundSelect:
r"""Return a SQL ``EXCEPT ALL`` of this select() construct against
the given selectables provided as positional arguments.
:param \*other: one or more elements with which to create a
UNION.
.. versionchanged:: 1.4.28
multiple elements are now accepted.
"""
return CompoundSelect._create_except_all(self, *other)
def intersect(
self, *other: _SelectStatementForCompoundArgument
) -> CompoundSelect:
r"""Return a SQL ``INTERSECT`` of this select() construct against
the given selectables provided as positional arguments.
:param \*other: one or more elements with which to create a
UNION.
.. versionchanged:: 1.4.28
multiple elements are now accepted.
:param \**kwargs: keyword arguments are forwarded to the constructor
for the newly created :class:`_sql.CompoundSelect` object.
"""
return CompoundSelect._create_intersect(self, *other)
def intersect_all(
self, *other: _SelectStatementForCompoundArgument
) -> CompoundSelect:
r"""Return a SQL ``INTERSECT ALL`` of this select() construct
against the given selectables provided as positional arguments.
:param \*other: one or more elements with which to create a
UNION.
.. versionchanged:: 1.4.28
multiple elements are now accepted.
:param \**kwargs: keyword arguments are forwarded to the constructor
for the newly created :class:`_sql.CompoundSelect` object.
"""
return CompoundSelect._create_intersect_all(self, *other)
class ScalarSelect(
roles.InElementRole, Generative, GroupedElement, ColumnElement[_T]
):
"""Represent a scalar subquery.
A :class:`_sql.ScalarSelect` is created by invoking the
:meth:`_sql.SelectBase.scalar_subquery` method. The object
then participates in other SQL expressions as a SQL column expression
within the :class:`_sql.ColumnElement` hierarchy.
.. seealso::
:meth:`_sql.SelectBase.scalar_subquery`
:ref:`tutorial_scalar_subquery` - in the 2.0 tutorial
"""
_traverse_internals: _TraverseInternalsType = [
("element", InternalTraversal.dp_clauseelement),
("type", InternalTraversal.dp_type),
]
_from_objects: List[FromClause] = []
_is_from_container = True
if not TYPE_CHECKING:
_is_implicitly_boolean = False
inherit_cache = True
element: SelectBase
def __init__(self, element: SelectBase) -> None:
self.element = element
self.type = element._scalar_type()
self._propagate_attrs = element._propagate_attrs
def __getattr__(self, attr: str) -> Any:
return getattr(self.element, attr)
def __getstate__(self) -> Dict[str, Any]:
return {"element": self.element, "type": self.type}
def __setstate__(self, state: Dict[str, Any]) -> None:
self.element = state["element"]
self.type = state["type"]
@property
def columns(self) -> NoReturn:
raise exc.InvalidRequestError(
"Scalar Select expression has no "
"columns; use this object directly "
"within a column-level expression."
)
c = columns
@_generative
def where(self, crit: _ColumnExpressionArgument[bool]) -> Self:
"""Apply a WHERE clause to the SELECT statement referred to
by this :class:`_expression.ScalarSelect`.
"""
self.element = cast("Select[Any]", self.element).where(crit)
return self
def self_group(self, against: Optional[OperatorType] = None) -> Self:
return self
if TYPE_CHECKING:
def _ungroup(self) -> Select[Any]: ...
@_generative
def correlate(
self,
*fromclauses: Union[Literal[None, False], _FromClauseArgument],
) -> Self:
r"""Return a new :class:`_expression.ScalarSelect`
which will correlate the given FROM
clauses to that of an enclosing :class:`_expression.Select`.
This method is mirrored from the :meth:`_sql.Select.correlate` method
of the underlying :class:`_sql.Select`. The method applies the
:meth:_sql.Select.correlate` method, then returns a new
:class:`_sql.ScalarSelect` against that statement.
.. versionadded:: 1.4 Previously, the
:meth:`_sql.ScalarSelect.correlate`
method was only available from :class:`_sql.Select`.
:param \*fromclauses: a list of one or more
:class:`_expression.FromClause`
constructs, or other compatible constructs (i.e. ORM-mapped
classes) to become part of the correlate collection.
.. seealso::
:meth:`_expression.ScalarSelect.correlate_except`
:ref:`tutorial_scalar_subquery` - in the 2.0 tutorial
"""
self.element = cast("Select[Any]", self.element).correlate(
*fromclauses
)
return self
@_generative
def correlate_except(
self,
*fromclauses: Union[Literal[None, False], _FromClauseArgument],
) -> Self:
r"""Return a new :class:`_expression.ScalarSelect`
which will omit the given FROM
clauses from the auto-correlation process.
This method is mirrored from the
:meth:`_sql.Select.correlate_except` method of the underlying
:class:`_sql.Select`. The method applies the
:meth:_sql.Select.correlate_except` method, then returns a new
:class:`_sql.ScalarSelect` against that statement.
.. versionadded:: 1.4 Previously, the
:meth:`_sql.ScalarSelect.correlate_except`
method was only available from :class:`_sql.Select`.
:param \*fromclauses: a list of one or more
:class:`_expression.FromClause`
constructs, or other compatible constructs (i.e. ORM-mapped
classes) to become part of the correlate-exception collection.
.. seealso::
:meth:`_expression.ScalarSelect.correlate`
:ref:`tutorial_scalar_subquery` - in the 2.0 tutorial
"""
self.element = cast("Select[Any]", self.element).correlate_except(
*fromclauses
)
return self
class Exists(UnaryExpression[bool]):
"""Represent an ``EXISTS`` clause.
See :func:`_sql.exists` for a description of usage.
An ``EXISTS`` clause can also be constructed from a :func:`_sql.select`
instance by calling :meth:`_sql.SelectBase.exists`.
"""
inherit_cache = True
element: Union[SelectStatementGrouping[Select[Any]], ScalarSelect[Any]]
def __init__(
self,
__argument: Optional[
Union[_ColumnsClauseArgument[Any], SelectBase, ScalarSelect[Any]]
] = None,
):
s: ScalarSelect[Any]
# TODO: this seems like we should be using coercions for this
if __argument is None:
s = Select(literal_column("*")).scalar_subquery()
elif isinstance(__argument, SelectBase):
s = __argument.scalar_subquery()
s._propagate_attrs = __argument._propagate_attrs
elif isinstance(__argument, ScalarSelect):
s = __argument
else:
s = Select(__argument).scalar_subquery()
UnaryExpression.__init__(
self,
s,
operator=operators.exists,
type_=type_api.BOOLEANTYPE,
wraps_column_expression=True,
)
@util.ro_non_memoized_property
def _from_objects(self) -> List[FromClause]:
return []
def _regroup(
self, fn: Callable[[Select[Any]], Select[Any]]
) -> SelectStatementGrouping[Select[Any]]:
element = self.element._ungroup()
new_element = fn(element)
return_value = new_element.self_group(against=operators.exists)
assert isinstance(return_value, SelectStatementGrouping)
return return_value
def select(self) -> Select[Tuple[bool]]:
r"""Return a SELECT of this :class:`_expression.Exists`.
e.g.::
stmt = exists(some_table.c.id).where(some_table.c.id == 5).select()
This will produce a statement resembling::
SELECT EXISTS (SELECT id FROM some_table WHERE some_table = :param) AS anon_1
.. seealso::
:func:`_expression.select` - general purpose
method which allows for arbitrary column lists.
""" # noqa
return Select(self)
def correlate(
self,
*fromclauses: Union[Literal[None, False], _FromClauseArgument],
) -> Self:
"""Apply correlation to the subquery noted by this
:class:`_sql.Exists`.
.. seealso::
:meth:`_sql.ScalarSelect.correlate`
"""
e = self._clone()
e.element = self._regroup(
lambda element: element.correlate(*fromclauses)
)
return e
def correlate_except(
self,
*fromclauses: Union[Literal[None, False], _FromClauseArgument],
) -> Self:
"""Apply correlation to the subquery noted by this
:class:`_sql.Exists`.
.. seealso::
:meth:`_sql.ScalarSelect.correlate_except`
"""
e = self._clone()
e.element = self._regroup(
lambda element: element.correlate_except(*fromclauses)
)
return e
def select_from(self, *froms: _FromClauseArgument) -> Self:
"""Return a new :class:`_expression.Exists` construct,
applying the given
expression to the :meth:`_expression.Select.select_from`
method of the select
statement contained.
.. note:: it is typically preferable to build a :class:`_sql.Select`
statement first, including the desired WHERE clause, then use the
:meth:`_sql.SelectBase.exists` method to produce an
:class:`_sql.Exists` object at once.
"""
e = self._clone()
e.element = self._regroup(lambda element: element.select_from(*froms))
return e
def where(self, *clause: _ColumnExpressionArgument[bool]) -> Self:
"""Return a new :func:`_expression.exists` construct with the
given expression added to
its WHERE clause, joined to the existing clause via AND, if any.
.. note:: it is typically preferable to build a :class:`_sql.Select`
statement first, including the desired WHERE clause, then use the
:meth:`_sql.SelectBase.exists` method to produce an
:class:`_sql.Exists` object at once.
"""
e = self._clone()
e.element = self._regroup(lambda element: element.where(*clause))
return e
class TextualSelect(SelectBase, ExecutableReturnsRows, Generative):
"""Wrap a :class:`_expression.TextClause` construct within a
:class:`_expression.SelectBase`
interface.
This allows the :class:`_expression.TextClause` object to gain a
``.c`` collection
and other FROM-like capabilities such as
:meth:`_expression.FromClause.alias`,
:meth:`_expression.SelectBase.cte`, etc.
The :class:`_expression.TextualSelect` construct is produced via the
:meth:`_expression.TextClause.columns`
method - see that method for details.
.. versionchanged:: 1.4 the :class:`_expression.TextualSelect`
class was renamed
from ``TextAsFrom``, to more correctly suit its role as a
SELECT-oriented object and not a FROM clause.
.. seealso::
:func:`_expression.text`
:meth:`_expression.TextClause.columns` - primary creation interface.
"""
__visit_name__ = "textual_select"
_label_style = LABEL_STYLE_NONE
_traverse_internals: _TraverseInternalsType = (
[
("element", InternalTraversal.dp_clauseelement),
("column_args", InternalTraversal.dp_clauseelement_list),
]
+ SupportsCloneAnnotations._clone_annotations_traverse_internals
+ HasCTE._has_ctes_traverse_internals
)
_is_textual = True
is_text = True
is_select = True
def __init__(
self,
text: TextClause,
columns: List[_ColumnExpressionArgument[Any]],
positional: bool = False,
) -> None:
self._init(
text,
# convert for ORM attributes->columns, etc
[
coercions.expect(roles.LabeledColumnExprRole, c)
for c in columns
],
positional,
)
def _init(
self,
text: TextClause,
columns: List[NamedColumn[Any]],
positional: bool = False,
) -> None:
self.element = text
self.column_args = columns
self.positional = positional
@HasMemoized_ro_memoized_attribute
def selected_columns(
self,
) -> ColumnCollection[str, KeyedColumnElement[Any]]:
"""A :class:`_expression.ColumnCollection`
representing the columns that
this SELECT statement or similar construct returns in its result set,
not including :class:`_sql.TextClause` constructs.
This collection differs from the :attr:`_expression.FromClause.columns`
collection of a :class:`_expression.FromClause` in that the columns
within this collection cannot be directly nested inside another SELECT
statement; a subquery must be applied first which provides for the
necessary parenthesization required by SQL.
For a :class:`_expression.TextualSelect` construct, the collection
contains the :class:`_expression.ColumnElement` objects that were
passed to the constructor, typically via the
:meth:`_expression.TextClause.columns` method.
.. versionadded:: 1.4
"""
return ColumnCollection(
(c.key, c) for c in self.column_args
).as_readonly()
@util.ro_non_memoized_property
def _all_selected_columns(self) -> _SelectIterable:
return self.column_args
def set_label_style(self, style: SelectLabelStyle) -> TextualSelect:
return self
def _ensure_disambiguated_names(self) -> TextualSelect:
return self
@_generative
def bindparams(
self,
*binds: BindParameter[Any],
**bind_as_values: Any,
) -> Self:
self.element = self.element.bindparams(*binds, **bind_as_values)
return self
def _generate_fromclause_column_proxies(
self,
fromclause: FromClause,
*,
proxy_compound_columns: Optional[
Iterable[Sequence[ColumnElement[Any]]]
] = None,
) -> None:
if TYPE_CHECKING:
assert isinstance(fromclause, Subquery)
if proxy_compound_columns:
fromclause._columns._populate_separate_keys(
c._make_proxy(fromclause, compound_select_cols=extra_cols)
for c, extra_cols in zip(
self.column_args, proxy_compound_columns
)
)
else:
fromclause._columns._populate_separate_keys(
c._make_proxy(fromclause) for c in self.column_args
)
def _scalar_type(self) -> Union[TypeEngine[Any], Any]:
return self.column_args[0].type
TextAsFrom = TextualSelect
"""Backwards compatibility with the previous name"""
class AnnotatedFromClause(Annotated):
def _copy_internals(self, **kw: Any) -> None:
super()._copy_internals(**kw)
if kw.get("ind_cols_on_fromclause", False):
ee = self._Annotated__element # type: ignore
self.c = ee.__class__.c.fget(self) # type: ignore
@util.ro_memoized_property
def c(self) -> ReadOnlyColumnCollection[str, KeyedColumnElement[Any]]:
"""proxy the .c collection of the underlying FromClause.
Originally implemented in 2008 as a simple load of the .c collection
when the annotated construct was created (see d3621ae961a), in modern
SQLAlchemy versions this can be expensive for statements constructed
with ORM aliases. So for #8796 SQLAlchemy 2.0 we instead proxy
it, which works just as well.
Two different use cases seem to require the collection either copied
from the underlying one, or unique to this AnnotatedFromClause.
See test_selectable->test_annotated_corresponding_column
"""
ee = self._Annotated__element # type: ignore
return ee.c # type: ignore