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# orm/query.py
# Copyright (C) 2005-2021 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""The Query class and support.
Defines the :class:`_query.Query` class, the central
construct used by the ORM to construct database queries.
The :class:`_query.Query` class should not be confused with the
:class:`_expression.Select` class, which defines database
SELECT operations at the SQL (non-ORM) level. ``Query`` differs from
``Select`` in that it returns ORM-mapped objects and interacts with an
ORM session, whereas the ``Select`` construct interacts directly with the
database to return iterable result sets.
"""
import itertools
import operator
import types
from . import exc as orm_exc
from . import interfaces
from . import loading
from . import util as orm_util
from .base import _assertions
from .context import _column_descriptions
from .context import _legacy_determine_last_joined_entity
from .context import _legacy_filter_by_entity_zero
from .context import LABEL_STYLE_LEGACY_ORM
from .context import ORMCompileState
from .context import ORMFromStatementCompileState
from .context import QueryContext
from .interfaces import ORMColumnsClauseRole
from .util import aliased
from .util import AliasedClass
from .util import object_mapper
from .util import with_parent
from .util import with_polymorphic
from .. import exc as sa_exc
from .. import inspect
from .. import inspection
from .. import log
from .. import sql
from .. import util
from ..sql import coercions
from ..sql import elements
from ..sql import expression
from ..sql import roles
from ..sql import Select
from ..sql import util as sql_util
from ..sql import visitors
from ..sql.annotation import SupportsCloneAnnotations
from ..sql.base import _entity_namespace_key
from ..sql.base import _generative
from ..sql.base import Executable
from ..sql.selectable import _MemoizedSelectEntities
from ..sql.selectable import _SelectFromElements
from ..sql.selectable import ForUpdateArg
from ..sql.selectable import GroupedElement
from ..sql.selectable import HasHints
from ..sql.selectable import HasPrefixes
from ..sql.selectable import HasSuffixes
from ..sql.selectable import LABEL_STYLE_TABLENAME_PLUS_COL
from ..sql.selectable import SelectBase
from ..sql.selectable import SelectStatementGrouping
from ..sql.visitors import InternalTraversal
from ..util import collections_abc
__all__ = ["Query", "QueryContext", "aliased"]
@inspection._self_inspects
@log.class_logger
class Query(
_SelectFromElements,
SupportsCloneAnnotations,
HasPrefixes,
HasSuffixes,
HasHints,
Executable,
):
"""ORM-level SQL construction object.
:class:`_query.Query`
is the source of all SELECT statements generated by the
ORM, both those formulated by end-user query operations as well as by
high level internal operations such as related collection loading. It
features a generative interface whereby successive calls return a new
:class:`_query.Query` object, a copy of the former with additional
criteria and options associated with it.
:class:`_query.Query` objects are normally initially generated using the
:meth:`~.Session.query` method of :class:`.Session`, and in
less common cases by instantiating the :class:`_query.Query` directly and
associating with a :class:`.Session` using the
:meth:`_query.Query.with_session`
method.
For a full walk through of :class:`_query.Query` usage, see the
:ref:`ormtutorial_toplevel`.
"""
# elements that are in Core and can be cached in the same way
_where_criteria = ()
_having_criteria = ()
_order_by_clauses = ()
_group_by_clauses = ()
_limit_clause = None
_offset_clause = None
_distinct = False
_distinct_on = ()
_for_update_arg = None
_correlate = ()
_auto_correlate = True
_from_obj = ()
_setup_joins = ()
_legacy_setup_joins = ()
_label_style = LABEL_STYLE_LEGACY_ORM
_memoized_select_entities = ()
_compile_options = ORMCompileState.default_compile_options
load_options = QueryContext.default_load_options
_params = util.EMPTY_DICT
# local Query builder state, not needed for
# compilation or execution
_aliased_generation = None
_enable_assertions = True
_last_joined_entity = None
_statement = None
# mirrors that of ClauseElement, used to propagate the "orm"
# plugin as well as the "subject" of the plugin, e.g. the mapper
# we are querying against.
_propagate_attrs = util.immutabledict()
def __init__(self, entities, session=None):
"""Construct a :class:`_query.Query` directly.
E.g.::
q = Query([User, Address], session=some_session)
The above is equivalent to::
q = some_session.query(User, Address)
:param entities: a sequence of entities and/or SQL expressions.
:param session: a :class:`.Session` with which the
:class:`_query.Query`
will be associated. Optional; a :class:`_query.Query`
can be associated
with a :class:`.Session` generatively via the
:meth:`_query.Query.with_session` method as well.
.. seealso::
:meth:`.Session.query`
:meth:`_query.Query.with_session`
"""
self.session = session
self._set_entities(entities)
def _set_propagate_attrs(self, values):
self._propagate_attrs = util.immutabledict(values)
return self
def _set_entities(self, entities):
self._raw_columns = [
coercions.expect(
roles.ColumnsClauseRole,
ent,
apply_propagate_attrs=self,
post_inspect=True,
)
for ent in util.to_list(entities)
]
def _entity_from_pre_ent_zero(self):
if not self._raw_columns:
return None
ent = self._raw_columns[0]
if "parententity" in ent._annotations:
return ent._annotations["parententity"]
elif isinstance(ent, ORMColumnsClauseRole):
return ent.entity
elif "bundle" in ent._annotations:
return ent._annotations["bundle"]
else:
# label, other SQL expression
for element in visitors.iterate(ent):
if "parententity" in element._annotations:
return element._annotations["parententity"]
else:
return None
def _only_full_mapper_zero(self, methname):
if (
len(self._raw_columns) != 1
or "parententity" not in self._raw_columns[0]._annotations
or not self._raw_columns[0].is_selectable
):
raise sa_exc.InvalidRequestError(
"%s() can only be used against "
"a single mapped class." % methname
)
return self._raw_columns[0]._annotations["parententity"]
def _set_select_from(self, obj, set_base_alias):
fa = [
coercions.expect(
roles.StrictFromClauseRole,
elem,
allow_select=True,
apply_propagate_attrs=self,
)
for elem in obj
]
self._compile_options += {"_set_base_alias": set_base_alias}
self._from_obj = tuple(fa)
@_generative
def _set_lazyload_from(self, state):
self.load_options += {"_lazy_loaded_from": state}
def _get_condition(self):
return self._no_criterion_condition(
"get", order_by=False, distinct=False
)
def _get_existing_condition(self):
self._no_criterion_assertion("get", order_by=False, distinct=False)
def _no_criterion_assertion(self, meth, order_by=True, distinct=True):
if not self._enable_assertions:
return
if (
self._where_criteria
or self._statement is not None
or self._from_obj
or self._legacy_setup_joins
or self._limit_clause is not None
or self._offset_clause is not None
or self._group_by_clauses
or (order_by and self._order_by_clauses)
or (distinct and self._distinct)
):
raise sa_exc.InvalidRequestError(
"Query.%s() being called on a "
"Query with existing criterion. " % meth
)
def _no_criterion_condition(self, meth, order_by=True, distinct=True):
self._no_criterion_assertion(meth, order_by, distinct)
self._from_obj = self._legacy_setup_joins = ()
if self._statement is not None:
self._compile_options += {"_statement": None}
self._where_criteria = ()
self._distinct = False
self._order_by_clauses = self._group_by_clauses = ()
def _no_clauseelement_condition(self, meth):
if not self._enable_assertions:
return
if self._order_by_clauses:
raise sa_exc.InvalidRequestError(
"Query.%s() being called on a "
"Query with existing criterion. " % meth
)
self._no_criterion_condition(meth)
def _no_statement_condition(self, meth):
if not self._enable_assertions:
return
if self._statement is not None:
raise sa_exc.InvalidRequestError(
(
"Query.%s() being called on a Query with an existing full "
"statement - can't apply criterion."
)
% meth
)
def _no_limit_offset(self, meth):
if not self._enable_assertions:
return
if self._limit_clause is not None or self._offset_clause is not None:
raise sa_exc.InvalidRequestError(
"Query.%s() being called on a Query which already has LIMIT "
"or OFFSET applied. Call %s() before limit() or offset() "
"are applied." % (meth, meth)
)
@property
def _has_row_limiting_clause(self):
return (
self._limit_clause is not None or self._offset_clause is not None
)
def _get_options(
self,
populate_existing=None,
version_check=None,
only_load_props=None,
refresh_state=None,
identity_token=None,
):
load_options = {}
compile_options = {}
if version_check:
load_options["_version_check"] = version_check
if populate_existing:
load_options["_populate_existing"] = populate_existing
if refresh_state:
load_options["_refresh_state"] = refresh_state
compile_options["_for_refresh_state"] = True
if only_load_props:
compile_options["_only_load_props"] = frozenset(only_load_props)
if identity_token:
load_options["_refresh_identity_token"] = identity_token
if load_options:
self.load_options += load_options
if compile_options:
self._compile_options += compile_options
return self
def _clone(self):
return self._generate()
@property
def statement(self):
"""The full SELECT statement represented by this Query.
The statement by default will not have disambiguating labels
applied to the construct unless with_labels(True) is called
first.
"""
# .statement can return the direct future.Select() construct here, as
# long as we are not using subsequent adaption features that
# are made against raw entities, e.g. from_self(), with_polymorphic(),
# select_entity_from(). If these features are being used, then
# the Select() we return will not have the correct .selected_columns
# collection and will not embed in subsequent queries correctly.
# We could find a way to make this collection "correct", however
# this would not be too different from doing the full compile as
# we are doing in any case, the Select() would still not have the
# proper state for other attributes like whereclause, order_by,
# and these features are all deprecated in any case.
#
# for these reasons, Query is not a Select, it remains an ORM
# object for which __clause_element__() must be called in order for
# it to provide a real expression object.
#
# from there, it starts to look much like Query itself won't be
# passed into the execute process and wont generate its own cache
# key; this will all occur in terms of the ORM-enabled Select.
if (
not self._compile_options._set_base_alias
and not self._compile_options._with_polymorphic_adapt_map
):
# if we don't have legacy top level aliasing features in use
# then convert to a future select() directly
stmt = self._statement_20(for_statement=True)
else:
stmt = self._compile_state(for_statement=True).statement
if self._params:
stmt = stmt.params(self._params)
return stmt
def _final_statement(self, legacy_query_style=True):
"""Return the 'final' SELECT statement for this :class:`.Query`.
This is the Core-only select() that will be rendered by a complete
compilation of this query, and is what .statement used to return
in 1.3.
This method creates a complete compile state so is fairly expensive.
"""
q = self._clone()
return q._compile_state(
use_legacy_query_style=legacy_query_style
).statement
def _statement_20(self, for_statement=False, use_legacy_query_style=True):
# TODO: this event needs to be deprecated, as it currently applies
# only to ORM query and occurs at this spot that is now more
# or less an artificial spot
if self.dispatch.before_compile:
for fn in self.dispatch.before_compile:
new_query = fn(self)
if new_query is not None and new_query is not self:
self = new_query
if not fn._bake_ok:
self._compile_options += {"_bake_ok": False}
compile_options = self._compile_options
compile_options += {
"_for_statement": for_statement,
"_use_legacy_query_style": use_legacy_query_style,
}
if self._statement is not None:
stmt = FromStatement(self._raw_columns, self._statement)
stmt.__dict__.update(
_with_options=self._with_options,
_with_context_options=self._with_context_options,
_compile_options=compile_options,
_execution_options=self._execution_options,
_propagate_attrs=self._propagate_attrs,
)
else:
# Query / select() internal attributes are 99% cross-compatible
stmt = Select.__new__(Select)
stmt.__dict__.update(self.__dict__)
stmt.__dict__.update(
_label_style=self._label_style,
_compile_options=compile_options,
_propagate_attrs=self._propagate_attrs,
)
stmt.__dict__.pop("session", None)
# ensure the ORM context is used to compile the statement, even
# if it has no ORM entities. This is so ORM-only things like
# _legacy_joins are picked up that wouldn't be picked up by the
# Core statement context
if "compile_state_plugin" not in stmt._propagate_attrs:
stmt._propagate_attrs = stmt._propagate_attrs.union(
{"compile_state_plugin": "orm", "plugin_subject": None}
)
return stmt
def subquery(
self,
name=None,
with_labels=False,
reduce_columns=False,
):
"""Return the full SELECT statement represented by
this :class:`_query.Query`, embedded within an
:class:`_expression.Alias`.
Eager JOIN generation within the query is disabled.
:param name: string name to be assigned as the alias;
this is passed through to :meth:`_expression.FromClause.alias`.
If ``None``, a name will be deterministically generated
at compile time.
:param with_labels: if True, :meth:`.with_labels` will be called
on the :class:`_query.Query` first to apply table-qualified labels
to all columns.
:param reduce_columns: if True,
:meth:`_expression.Select.reduce_columns` will
be called on the resulting :func:`_expression.select` construct,
to remove same-named columns where one also refers to the other
via foreign key or WHERE clause equivalence.
"""
q = self.enable_eagerloads(False)
if with_labels:
q = q.set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)
q = q.statement
if reduce_columns:
q = q.reduce_columns()
return q.alias(name=name)
def cte(self, name=None, recursive=False):
r"""Return the full SELECT statement represented by this
:class:`_query.Query` represented as a common table expression (CTE).
Parameters and usage are the same as those of the
:meth:`_expression.SelectBase.cte` method; see that method for
further details.
Here is the `PostgreSQL WITH
RECURSIVE example
<http://www.postgresql.org/docs/8.4/static/queries-with.html>`_.
Note that, in this example, the ``included_parts`` cte and the
``incl_alias`` alias of it are Core selectables, which
means the columns are accessed via the ``.c.`` attribute. The
``parts_alias`` object is an :func:`_orm.aliased` instance of the
``Part`` entity, so column-mapped attributes are available
directly::
from sqlalchemy.orm import aliased
class Part(Base):
__tablename__ = 'part'
part = Column(String, primary_key=True)
sub_part = Column(String, primary_key=True)
quantity = Column(Integer)
included_parts = session.query(
Part.sub_part,
Part.part,
Part.quantity).\
filter(Part.part=="our part").\
cte(name="included_parts", recursive=True)
incl_alias = aliased(included_parts, name="pr")
parts_alias = aliased(Part, name="p")
included_parts = included_parts.union_all(
session.query(
parts_alias.sub_part,
parts_alias.part,
parts_alias.quantity).\
filter(parts_alias.part==incl_alias.c.sub_part)
)
q = session.query(
included_parts.c.sub_part,
func.sum(included_parts.c.quantity).
label('total_quantity')
).\
group_by(included_parts.c.sub_part)
.. seealso::
:meth:`_expression.HasCTE.cte`
"""
return self.enable_eagerloads(False).statement.cte(
name=name, recursive=recursive
)
def label(self, name):
"""Return the full SELECT statement represented by this
:class:`_query.Query`, converted
to a scalar subquery with a label of the given name.
Analogous to :meth:`sqlalchemy.sql.expression.SelectBase.label`.
"""
return self.enable_eagerloads(False).statement.label(name)
@util.deprecated(
"1.4",
"The :meth:`_query.Query.as_scalar` method is deprecated and will be "
"removed in a future release. Please refer to "
":meth:`_query.Query.scalar_subquery`.",
)
def as_scalar(self):
"""Return the full SELECT statement represented by this
:class:`_query.Query`, converted to a scalar subquery.
"""
return self.scalar_subquery()
def scalar_subquery(self):
"""Return the full SELECT statement represented by this
:class:`_query.Query`, converted to a scalar subquery.
Analogous to
:meth:`sqlalchemy.sql.expression.SelectBase.scalar_subquery`.
.. versionchanged:: 1.4 The :meth:`_query.Query.scalar_subquery`
method replaces the :meth:`_query.Query.as_scalar` method.
"""
return self.enable_eagerloads(False).statement.scalar_subquery()
@property
def selectable(self):
"""Return the :class:`_expression.Select` object emitted by this
:class:`_query.Query`.
Used for :func:`_sa.inspect` compatibility, this is equivalent to::
query.enable_eagerloads(False).with_labels().statement
"""
return self.__clause_element__()
def __clause_element__(self):
return (
self._with_compile_options(
_enable_eagerloads=False, _render_for_subquery=True
)
.set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)
.statement
)
@_generative
def only_return_tuples(self, value):
"""When set to True, the query results will always be a tuple.
This is specifically for single element queries. The default is False.
.. versionadded:: 1.2.5
.. seealso::
:meth:`_query.Query.is_single_entity`
"""
self.load_options += dict(_only_return_tuples=value)
@property
def is_single_entity(self):
"""Indicates if this :class:`_query.Query`
returns tuples or single entities.
Returns True if this query returns a single entity for each instance
in its result list, and False if this query returns a tuple of entities
for each result.
.. versionadded:: 1.3.11
.. seealso::
:meth:`_query.Query.only_return_tuples`
"""
return (
not self.load_options._only_return_tuples
and len(self._raw_columns) == 1
and "parententity" in self._raw_columns[0]._annotations
and isinstance(
self._raw_columns[0]._annotations["parententity"],
ORMColumnsClauseRole,
)
)
@_generative
def enable_eagerloads(self, value):
"""Control whether or not eager joins and subqueries are
rendered.
When set to False, the returned Query will not render
eager joins regardless of :func:`~sqlalchemy.orm.joinedload`,
:func:`~sqlalchemy.orm.subqueryload` options
or mapper-level ``lazy='joined'``/``lazy='subquery'``
configurations.
This is used primarily when nesting the Query's
statement into a subquery or other
selectable, or when using :meth:`_query.Query.yield_per`.
"""
self._compile_options += {"_enable_eagerloads": value}
@_generative
def _with_compile_options(self, **opt):
self._compile_options += opt
@util.deprecated_20(
":meth:`_orm.Query.with_labels` and :meth:`_orm.Query.apply_labels`",
alternative="Use set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL) "
"instead.",
)
def with_labels(self):
return self.set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)
apply_labels = with_labels
@property
def get_label_style(self):
"""
Retrieve the current label style.
.. versionadded:: 1.4
"""
return self._label_style
def set_label_style(self, style):
"""Apply column labels to the return value of Query.statement.
Indicates that this Query's `statement` accessor should return
a SELECT statement that applies labels to all columns in the
form <tablename>_<columnname>; this is commonly used to
disambiguate columns from multiple tables which have the same
name.
When the `Query` actually issues SQL to load rows, it always
uses column labeling.
.. note:: The :meth:`_query.Query.set_label_style` method *only* applies
the output of :attr:`_query.Query.statement`, and *not* to any of
the result-row invoking systems of :class:`_query.Query` itself,
e.g.
:meth:`_query.Query.first`, :meth:`_query.Query.all`, etc.
To execute
a query using :meth:`_query.Query.set_label_style`, invoke the
:attr:`_query.Query.statement` using :meth:`.Session.execute`::
result = session.execute(
query
.set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)
.statement
)
.. versionadded:: 1.4
""" # noqa
if self._label_style is not style:
self = self._generate()
self._label_style = style
return self
@_generative
def enable_assertions(self, value):
"""Control whether assertions are generated.
When set to False, the returned Query will
not assert its state before certain operations,
including that LIMIT/OFFSET has not been applied
when filter() is called, no criterion exists
when get() is called, and no "from_statement()"
exists when filter()/order_by()/group_by() etc.
is called. This more permissive mode is used by
custom Query subclasses to specify criterion or
other modifiers outside of the usual usage patterns.
Care should be taken to ensure that the usage
pattern is even possible. A statement applied
by from_statement() will override any criterion
set by filter() or order_by(), for example.
"""
self._enable_assertions = value
@property
def whereclause(self):
"""A readonly attribute which returns the current WHERE criterion for
this Query.
This returned value is a SQL expression construct, or ``None`` if no
criterion has been established.
"""
return sql.elements.BooleanClauseList._construct_for_whereclause(
self._where_criteria
)
@_generative
def _with_current_path(self, path):
"""indicate that this query applies to objects loaded
within a certain path.
Used by deferred loaders (see strategies.py) which transfer
query options from an originating query to a newly generated
query intended for the deferred load.
"""
self._compile_options += {"_current_path": path}
@_generative
@_assertions(_no_clauseelement_condition)
@util.deprecated_20(
":meth:`_orm.Query.with_polymorphic`",
alternative="Use the orm.with_polymorphic() standalone function",
)
def with_polymorphic(
self, cls_or_mappers, selectable=None, polymorphic_on=None
):
"""Load columns for inheriting classes.
This is a legacy method which is replaced by the
:func:`_orm.with_polymorphic` function.
.. warning:: The :meth:`_orm.Query.with_polymorphic` method does
**not** support 1.4/2.0 style features including
:func:`_orm.with_loader_criteria`. Please migrate code
to use :func:`_orm.with_polymorphic`.
:meth:`_query.Query.with_polymorphic` applies transformations
to the "main" mapped class represented by this :class:`_query.Query`.
The "main" mapped class here means the :class:`_query.Query`
object's first argument is a full class, i.e.
``session.query(SomeClass)``. These transformations allow additional
tables to be present in the FROM clause so that columns for a
joined-inheritance subclass are available in the query, both for the
purposes of load-time efficiency as well as the ability to use
these columns at query time.
.. seealso::
:ref:`with_polymorphic` - illustrates current patterns
"""
entity = _legacy_filter_by_entity_zero(self)
wp = with_polymorphic(
entity,
cls_or_mappers,
selectable=selectable,
polymorphic_on=polymorphic_on,
)
self._compile_options = self._compile_options.add_to_element(
"_with_polymorphic_adapt_map", ((entity, inspect(wp)),)
)
@_generative
def yield_per(self, count):
r"""Yield only ``count`` rows at a time.
The purpose of this method is when fetching very large result sets
(> 10K rows), to batch results in sub-collections and yield them
out partially, so that the Python interpreter doesn't need to declare
very large areas of memory which is both time consuming and leads
to excessive memory use. The performance from fetching hundreds of
thousands of rows can often double when a suitable yield-per setting
(e.g. approximately 1000) is used, even with DBAPIs that buffer
rows (which are most).
As of SQLAlchemy 1.4, the :meth:`_orm.Query.yield_per` method is
equivalent to using the ``yield_per`` execution option at the ORM
level. See the section :ref:`orm_queryguide_yield_per` for further
background on this option.
"""
self.load_options += {"_yield_per": count}
@util.deprecated_20(
":meth:`_orm.Query.get`",
alternative="The method is now available as :meth:`_orm.Session.get`",
becomes_legacy=True,
)
def get(self, ident):
"""Return an instance based on the given primary key identifier,
or ``None`` if not found.
E.g.::
my_user = session.query(User).get(5)
some_object = session.query(VersionedFoo).get((5, 10))
some_object = session.query(VersionedFoo).get(
{"id": 5, "version_id": 10})
:meth:`_query.Query.get` is special in that it provides direct
access to the identity map of the owning :class:`.Session`.
If the given primary key identifier is present
in the local identity map, the object is returned
directly from this collection and no SQL is emitted,
unless the object has been marked fully expired.
If not present,
a SELECT is performed in order to locate the object.
:meth:`_query.Query.get` also will perform a check if
the object is present in the identity map and
marked as expired - a SELECT
is emitted to refresh the object as well as to
ensure that the row is still present.
If not, :class:`~sqlalchemy.orm.exc.ObjectDeletedError` is raised.
:meth:`_query.Query.get` is only used to return a single
mapped instance, not multiple instances or
individual column constructs, and strictly
on a single primary key value. The originating
:class:`_query.Query` must be constructed in this way,
i.e. against a single mapped entity,
with no additional filtering criterion. Loading
options via :meth:`_query.Query.options` may be applied
however, and will be used if the object is not
yet locally present.
:param ident: A scalar, tuple, or dictionary representing the
primary key. For a composite (e.g. multiple column) primary key,
a tuple or dictionary should be passed.
For a single-column primary key, the scalar calling form is typically
the most expedient. If the primary key of a row is the value "5",
the call looks like::
my_object = query.get(5)
The tuple form contains primary key values typically in
the order in which they correspond to the mapped
:class:`_schema.Table`
object's primary key columns, or if the
:paramref:`_orm.Mapper.primary_key` configuration parameter were
used, in
the order used for that parameter. For example, if the primary key
of a row is represented by the integer
digits "5, 10" the call would look like::
my_object = query.get((5, 10))
The dictionary form should include as keys the mapped attribute names
corresponding to each element of the primary key. If the mapped class
has the attributes ``id``, ``version_id`` as the attributes which
store the object's primary key value, the call would look like::
my_object = query.get({"id": 5, "version_id": 10})
.. versionadded:: 1.3 the :meth:`_query.Query.get`
method now optionally
accepts a dictionary of attribute names to values in order to
indicate a primary key identifier.
:return: The object instance, or ``None``.
"""
self._no_criterion_assertion("get", order_by=False, distinct=False)
# we still implement _get_impl() so that baked query can override
# it
return self._get_impl(ident, loading.load_on_pk_identity)
def _get_impl(self, primary_key_identity, db_load_fn, identity_token=None):
mapper = self._only_full_mapper_zero("get")
return self.session._get_impl(
mapper,
primary_key_identity,
db_load_fn,
populate_existing=self.load_options._populate_existing,
with_for_update=self._for_update_arg,
options=self._with_options,
identity_token=identity_token,
execution_options=self._execution_options,
)
@property
def lazy_loaded_from(self):
"""An :class:`.InstanceState` that is using this :class:`_query.Query`
for a lazy load operation.
.. deprecated:: 1.4 This attribute should be viewed via the
:attr:`.ORMExecuteState.lazy_loaded_from` attribute, within
the context of the :meth:`.SessionEvents.do_orm_execute`
event.
.. seealso::
:attr:`.ORMExecuteState.lazy_loaded_from`
"""
return self.load_options._lazy_loaded_from
@property
def _current_path(self):
return self._compile_options._current_path
@_generative
def correlate(self, *fromclauses):
"""Return a :class:`.Query` construct which will correlate the given
FROM clauses to that of an enclosing :class:`.Query` or
:func:`~.expression.select`.
The method here accepts mapped classes, :func:`.aliased` constructs,
and :func:`.mapper` constructs as arguments, which are resolved into
expression constructs, in addition to appropriate expression
constructs.
The correlation arguments are ultimately passed to
:meth:`_expression.Select.correlate`
after coercion to expression constructs.
The correlation arguments take effect in such cases
as when :meth:`_query.Query.from_self` is used, or when
a subquery as returned by :meth:`_query.Query.subquery` is
embedded in another :func:`_expression.select` construct.
"""
self._auto_correlate = False
if fromclauses and fromclauses[0] in {None, False}:
self._correlate = ()
else:
self._correlate = set(self._correlate).union(
coercions.expect(roles.FromClauseRole, f) for f in fromclauses
)
@_generative
def autoflush(self, setting):
"""Return a Query with a specific 'autoflush' setting.
As of SQLAlchemy 1.4, the :meth:`_orm.Query.autoflush` method
is equivalent to using the ``autoflush`` execution option at the
ORM level. See the section :ref:`orm_queryguide_autoflush` for
further background on this option.
"""
self.load_options += {"_autoflush": setting}
@_generative
def populate_existing(self):
"""Return a :class:`_query.Query`
that will expire and refresh all instances
as they are loaded, or reused from the current :class:`.Session`.
As of SQLAlchemy 1.4, the :meth:`_orm.Query.populate_existing` method
is equivalent to using the ``populate_existing`` execution option at
the ORM level. See the section :ref:`orm_queryguide_populate_existing`
for further background on this option.
"""
self.load_options += {"_populate_existing": True}
@_generative
def _with_invoke_all_eagers(self, value):
"""Set the 'invoke all eagers' flag which causes joined- and
subquery loaders to traverse into already-loaded related objects
and collections.
Default is that of :attr:`_query.Query._invoke_all_eagers`.
"""
self.load_options += {"_invoke_all_eagers": value}
@util.deprecated_20(
":meth:`_orm.Query.with_parent`",
alternative="Use the :func:`_orm.with_parent` standalone construct.",
becomes_legacy=True,
)
@util.preload_module("sqlalchemy.orm.relationships")
def with_parent(self, instance, property=None, from_entity=None): # noqa
"""Add filtering criterion that relates the given instance
to a child object or collection, using its attribute state
as well as an established :func:`_orm.relationship()`
configuration.
The method uses the :func:`.with_parent` function to generate
the clause, the result of which is passed to
:meth:`_query.Query.filter`.
Parameters are the same as :func:`.with_parent`, with the exception
that the given property can be None, in which case a search is
performed against this :class:`_query.Query` object's target mapper.
:param instance:
An instance which has some :func:`_orm.relationship`.
:param property:
String property name, or class-bound attribute, which indicates
what relationship from the instance should be used to reconcile the
parent/child relationship.
:param from_entity:
Entity in which to consider as the left side. This defaults to the
"zero" entity of the :class:`_query.Query` itself.
"""
relationships = util.preloaded.orm_relationships
if from_entity:
entity_zero = inspect(from_entity)
else:
entity_zero = _legacy_filter_by_entity_zero(self)
if property is None:
# TODO: deprecate, property has to be supplied
mapper = object_mapper(instance)
for prop in mapper.iterate_properties:
if (
isinstance(prop, relationships.RelationshipProperty)
and prop.mapper is entity_zero.mapper
):
property = prop # noqa
break
else:
raise sa_exc.InvalidRequestError(
"Could not locate a property which relates instances "
"of class '%s' to instances of class '%s'"
% (
entity_zero.mapper.class_.__name__,
instance.__class__.__name__,
)
)
return self.filter(with_parent(instance, property, entity_zero.entity))
@_generative
def add_entity(self, entity, alias=None):
"""add a mapped entity to the list of result columns
to be returned."""
if alias is not None:
# TODO: deprecate
entity = aliased(entity, alias)
self._raw_columns = list(self._raw_columns)
self._raw_columns.append(
coercions.expect(
roles.ColumnsClauseRole, entity, apply_propagate_attrs=self
)
)
@_generative
def with_session(self, session):
"""Return a :class:`_query.Query` that will use the given
:class:`.Session`.
While the :class:`_query.Query`
object is normally instantiated using the
:meth:`.Session.query` method, it is legal to build the
:class:`_query.Query`
directly without necessarily using a :class:`.Session`. Such a
:class:`_query.Query` object, or any :class:`_query.Query`
already associated
with a different :class:`.Session`, can produce a new
:class:`_query.Query`
object associated with a target session using this method::
from sqlalchemy.orm import Query
query = Query([MyClass]).filter(MyClass.id == 5)
result = query.with_session(my_session).one()
"""
self.session = session
@util.deprecated_20(
":meth:`_query.Query.from_self`",
alternative="The new approach is to use the :func:`.orm.aliased` "
"construct in conjunction with a subquery. See the section "
":ref:`Selecting from the query itself as a subquery "
"<migration_20_query_from_self>` in the 2.0 migration notes for an "
"example.",
)
def from_self(self, *entities):
r"""return a Query that selects from this Query's
SELECT statement.
:meth:`_query.Query.from_self` essentially turns the SELECT statement
into a SELECT of itself. Given a query such as::
q = session.query(User).filter(User.name.like('e%'))
Given the :meth:`_query.Query.from_self` version::
q = session.query(User).filter(User.name.like('e%')).from_self()
This query renders as:
.. sourcecode:: sql
SELECT anon_1.user_id AS anon_1_user_id,
anon_1.user_name AS anon_1_user_name
FROM (SELECT "user".id AS user_id, "user".name AS user_name
FROM "user"
WHERE "user".name LIKE :name_1) AS anon_1
There are lots of cases where :meth:`_query.Query.from_self`
may be useful.
A simple one is where above, we may want to apply a row LIMIT to
the set of user objects we query against, and then apply additional
joins against that row-limited set::
q = session.query(User).filter(User.name.like('e%')).\
limit(5).from_self().\
join(User.addresses).filter(Address.email.like('q%'))
The above query joins to the ``Address`` entity but only against the
first five results of the ``User`` query:
.. sourcecode:: sql
SELECT anon_1.user_id AS anon_1_user_id,
anon_1.user_name AS anon_1_user_name
FROM (SELECT "user".id AS user_id, "user".name AS user_name
FROM "user"
WHERE "user".name LIKE :name_1
LIMIT :param_1) AS anon_1
JOIN address ON anon_1.user_id = address.user_id
WHERE address.email LIKE :email_1
**Automatic Aliasing**
Another key behavior of :meth:`_query.Query.from_self`
is that it applies
**automatic aliasing** to the entities inside the subquery, when
they are referenced on the outside. Above, if we continue to
refer to the ``User`` entity without any additional aliasing applied
to it, those references will be in terms of the subquery::
q = session.query(User).filter(User.name.like('e%')).\
limit(5).from_self().\
join(User.addresses).filter(Address.email.like('q%')).\
order_by(User.name)
The ORDER BY against ``User.name`` is aliased to be in terms of the
inner subquery:
.. sourcecode:: sql
SELECT anon_1.user_id AS anon_1_user_id,
anon_1.user_name AS anon_1_user_name
FROM (SELECT "user".id AS user_id, "user".name AS user_name
FROM "user"
WHERE "user".name LIKE :name_1
LIMIT :param_1) AS anon_1
JOIN address ON anon_1.user_id = address.user_id
WHERE address.email LIKE :email_1 ORDER BY anon_1.user_name
The automatic aliasing feature only works in a **limited** way,
for simple filters and orderings. More ambitious constructions
such as referring to the entity in joins should prefer to use
explicit subquery objects, typically making use of the
:meth:`_query.Query.subquery`
method to produce an explicit subquery object.
Always test the structure of queries by viewing the SQL to ensure
a particular structure does what's expected!
**Changing the Entities**
:meth:`_query.Query.from_self`
also includes the ability to modify what
columns are being queried. In our example, we want ``User.id``
to be queried by the inner query, so that we can join to the
``Address`` entity on the outside, but we only wanted the outer
query to return the ``Address.email`` column::
q = session.query(User).filter(User.name.like('e%')).\
limit(5).from_self(Address.email).\
join(User.addresses).filter(Address.email.like('q%'))
yielding:
.. sourcecode:: sql
SELECT address.email AS address_email
FROM (SELECT "user".id AS user_id, "user".name AS user_name
FROM "user"
WHERE "user".name LIKE :name_1
LIMIT :param_1) AS anon_1
JOIN address ON anon_1.user_id = address.user_id
WHERE address.email LIKE :email_1
**Looking out for Inner / Outer Columns**
Keep in mind that when referring to columns that originate from
inside the subquery, we need to ensure they are present in the
columns clause of the subquery itself; this is an ordinary aspect of
SQL. For example, if we wanted to load from a joined entity inside
the subquery using :func:`.contains_eager`, we need to add those
columns. Below illustrates a join of ``Address`` to ``User``,
then a subquery, and then we'd like :func:`.contains_eager` to access
the ``User`` columns::
q = session.query(Address).join(Address.user).\
filter(User.name.like('e%'))
q = q.add_entity(User).from_self().\
options(contains_eager(Address.user))
We use :meth:`_query.Query.add_entity` above **before** we call
:meth:`_query.Query.from_self`
so that the ``User`` columns are present
in the inner subquery, so that they are available to the
:func:`.contains_eager` modifier we are using on the outside,
producing:
.. sourcecode:: sql
SELECT anon_1.address_id AS anon_1_address_id,
anon_1.address_email AS anon_1_address_email,
anon_1.address_user_id AS anon_1_address_user_id,
anon_1.user_id AS anon_1_user_id,
anon_1.user_name AS anon_1_user_name
FROM (
SELECT address.id AS address_id,
address.email AS address_email,
address.user_id AS address_user_id,
"user".id AS user_id,
"user".name AS user_name
FROM address JOIN "user" ON "user".id = address.user_id
WHERE "user".name LIKE :name_1) AS anon_1
If we didn't call ``add_entity(User)``, but still asked
:func:`.contains_eager` to load the ``User`` entity, it would be
forced to add the table on the outside without the correct
join criteria - note the ``anon1, "user"`` phrase at
the end:
.. sourcecode:: sql
-- incorrect query
SELECT anon_1.address_id AS anon_1_address_id,
anon_1.address_email AS anon_1_address_email,
anon_1.address_user_id AS anon_1_address_user_id,
"user".id AS user_id,
"user".name AS user_name
FROM (
SELECT address.id AS address_id,
address.email AS address_email,
address.user_id AS address_user_id
FROM address JOIN "user" ON "user".id = address.user_id
WHERE "user".name LIKE :name_1) AS anon_1, "user"
:param \*entities: optional list of entities which will replace
those being selected.
"""
return self._from_self(*entities)
def _from_self(self, *entities):
fromclause = (
self.set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)
.correlate(None)
.subquery()
._anonymous_fromclause()
)
q = self._from_selectable(fromclause)
if entities:
q._set_entities(entities)
return q
@_generative
def _set_enable_single_crit(self, val):
self._compile_options += {"_enable_single_crit": val}
@_generative
def _from_selectable(self, fromclause, set_entity_from=True):
for attr in (
"_where_criteria",
"_order_by_clauses",
"_group_by_clauses",
"_limit_clause",
"_offset_clause",
"_last_joined_entity",
"_legacy_setup_joins",
"_distinct",
"_distinct_on",
"_having_criteria",
"_prefixes",
"_suffixes",
):
self.__dict__.pop(attr, None)
self._set_select_from([fromclause], set_entity_from)
self._compile_options += {
"_enable_single_crit": False,
}
# this enables clause adaptation for non-ORM
# expressions.
# legacy. see test/orm/test_froms.py for various
# "oldstyle" tests that rely on this and the corresponding
# "newtyle" that do not.
self._compile_options += {"_orm_only_from_obj_alias": False}
@util.deprecated(
"1.4",
":meth:`_query.Query.values` "
"is deprecated and will be removed in a "
"future release. Please use :meth:`_query.Query.with_entities`",
)
def values(self, *columns):
"""Return an iterator yielding result tuples corresponding
to the given list of columns
"""
if not columns:
return iter(())
q = self._clone().enable_eagerloads(False)
q._set_entities(columns)
if not q.load_options._yield_per:
q.load_options += {"_yield_per": 10}
return iter(q)
_values = values
@util.deprecated(
"1.4",
":meth:`_query.Query.value` "
"is deprecated and will be removed in a "
"future release. Please use :meth:`_query.Query.with_entities` "
"in combination with :meth:`_query.Query.scalar`",
)
def value(self, column):
"""Return a scalar result corresponding to the given
column expression.
"""
try:
return next(self.values(column))[0]
except StopIteration:
return None
@_generative
def with_entities(self, *entities):
r"""Return a new :class:`_query.Query`
replacing the SELECT list with the
given entities.
e.g.::
# Users, filtered on some arbitrary criterion
# and then ordered by related email address
q = session.query(User).\
join(User.address).\
filter(User.name.like('%ed%')).\
order_by(Address.email)
# given *only* User.id==5, Address.email, and 'q', what
# would the *next* User in the result be ?
subq = q.with_entities(Address.email).\
order_by(None).\
filter(User.id==5).\
subquery()
q = q.join((subq, subq.c.email < Address.email)).\
limit(1)
"""
_MemoizedSelectEntities._generate_for_statement(self)
self._set_entities(entities)
@_generative
def add_columns(self, *column):
"""Add one or more column expressions to the list
of result columns to be returned."""
self._raw_columns = list(self._raw_columns)
self._raw_columns.extend(
coercions.expect(
roles.ColumnsClauseRole,
c,
apply_propagate_attrs=self,
post_inspect=True,
)
for c in column
)
@util.deprecated(
"1.4",
":meth:`_query.Query.add_column` "
"is deprecated and will be removed in a "
"future release. Please use :meth:`_query.Query.add_columns`",
)
def add_column(self, column):
"""Add a column expression to the list of result columns to be
returned.
"""
return self.add_columns(column)
@_generative
def options(self, *args):
"""Return a new :class:`_query.Query` object,
applying the given list of
mapper options.
Most supplied options regard changing how column- and
relationship-mapped attributes are loaded.
.. seealso::
:ref:`deferred_options`
:ref:`relationship_loader_options`
"""
opts = tuple(util.flatten_iterator(args))
if self._compile_options._current_path:
for opt in opts:
if opt._is_legacy_option:
opt.process_query_conditionally(self)
else:
for opt in opts:
if opt._is_legacy_option:
opt.process_query(self)
self._with_options += opts
def with_transformation(self, fn):
"""Return a new :class:`_query.Query` object transformed by
the given function.
E.g.::
def filter_something(criterion):
def transform(q):
return q.filter(criterion)
return transform
q = q.with_transformation(filter_something(x==5))
This allows ad-hoc recipes to be created for :class:`_query.Query`
objects. See the example at :ref:`hybrid_transformers`.
"""
return fn(self)
def get_execution_options(self):
"""Get the non-SQL options which will take effect during execution.
.. versionadded:: 1.3
.. seealso::
:meth:`_query.Query.execution_options`
"""
return self._execution_options
@_generative
def execution_options(self, **kwargs):
"""Set non-SQL options which take effect during execution.
Options allowed here include all of those accepted by
:meth:`_engine.Connection.execution_options`, as well as a series
of ORM specific options:
``populate_existing=True`` - equivalent to using
:meth:`_orm.Query.populate_existing`
``autoflush=True|False`` - equivalent to using
:meth:`_orm.Query.autoflush`
``yield_per=<value>`` - equivalent to using
:meth:`_orm.Query.yield_per`
Note that the ``stream_results`` execution option is enabled
automatically if the :meth:`~sqlalchemy.orm.query.Query.yield_per()`
method or execution option is used.
The execution options may also be specified on a per execution basis
when using :term:`2.0 style` queries via the
:paramref:`_orm.Session.execution_options` parameter.
.. versionadded:: 1.4 - added ORM options to
:meth:`_orm.Query.execution_options`
.. seealso::
:ref:`engine_stream_results`
:meth:`_query.Query.get_execution_options`
"""
self._execution_options = self._execution_options.union(kwargs)
@_generative
def with_for_update(
self,
read=False,
nowait=False,
of=None,
skip_locked=False,
key_share=False,
):
"""return a new :class:`_query.Query`
with the specified options for the
``FOR UPDATE`` clause.
The behavior of this method is identical to that of
:meth:`_expression.GenerativeSelect.with_for_update`.
When called with no arguments,
the resulting ``SELECT`` statement will have a ``FOR UPDATE`` clause
appended. When additional arguments are specified, backend-specific
options such as ``FOR UPDATE NOWAIT`` or ``LOCK IN SHARE MODE``
can take effect.
E.g.::
q = sess.query(User).populate_existing().with_for_update(nowait=True, of=User)
The above query on a PostgreSQL backend will render like::
SELECT users.id AS users_id FROM users FOR UPDATE OF users NOWAIT
.. note:: It is generally a good idea to combine the use of the
:meth:`_orm.Query.populate_existing` method when using the
:meth:`_orm.Query.with_for_update` method. The purpose of
:meth:`_orm.Query.populate_existing` is to force all the data read
from the SELECT to be populated into the ORM objects returned,
even if these objects are already in the :term:`identity map`.
.. seealso::
:meth:`_expression.GenerativeSelect.with_for_update`
- Core level method with
full argument and behavioral description.
:meth:`_orm.Query.populate_existing` - overwrites attributes of
objects already loaded in the identity map.
""" # noqa: E501
self._for_update_arg = ForUpdateArg(
read=read,
nowait=nowait,
of=of,
skip_locked=skip_locked,
key_share=key_share,
)
@_generative
def params(self, *args, **kwargs):
r"""Add values for bind parameters which may have been
specified in filter().
Parameters may be specified using \**kwargs, or optionally a single
dictionary as the first positional argument. The reason for both is
that \**kwargs is convenient, however some parameter dictionaries
contain unicode keys in which case \**kwargs cannot be used.
"""
if len(args) == 1:
kwargs.update(args[0])
elif len(args) > 0:
raise sa_exc.ArgumentError(
"params() takes zero or one positional argument, "
"which is a dictionary."
)
self._params = self._params.union(kwargs)
def where(self, *criterion):
"""A synonym for :meth:`.Query.filter`.
.. versionadded:: 1.4
"""
return self.filter(*criterion)
@_generative
@_assertions(_no_statement_condition, _no_limit_offset)
def filter(self, *criterion):
r"""Apply the given filtering criterion to a copy
of this :class:`_query.Query`, using SQL expressions.
e.g.::
session.query(MyClass).filter(MyClass.name == 'some name')
Multiple criteria may be specified as comma separated; the effect
is that they will be joined together using the :func:`.and_`
function::
session.query(MyClass).\
filter(MyClass.name == 'some name', MyClass.id > 5)
The criterion is any SQL expression object applicable to the
WHERE clause of a select. String expressions are coerced
into SQL expression constructs via the :func:`_expression.text`
construct.
.. seealso::
:meth:`_query.Query.filter_by` - filter on keyword expressions.
"""
for criterion in list(criterion):
criterion = coercions.expect(
roles.WhereHavingRole, criterion, apply_propagate_attrs=self
)
# legacy vvvvvvvvvvvvvvvvvvvvvvvvvvv
if self._aliased_generation:
criterion = sql_util._deep_annotate(
criterion, {"aliased_generation": self._aliased_generation}
)
# legacy ^^^^^^^^^^^^^^^^^^^^^^^^^^^
self._where_criteria += (criterion,)
@util.memoized_property
def _last_joined_entity(self):
if self._legacy_setup_joins:
return _legacy_determine_last_joined_entity(
self._legacy_setup_joins, self._entity_from_pre_ent_zero()
)
else:
return None
def _filter_by_zero(self):
if self._legacy_setup_joins:
_last_joined_entity = self._last_joined_entity
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]
def filter_by(self, **kwargs):
r"""Apply the given filtering criterion to a copy
of this :class:`_query.Query`, using keyword expressions.
e.g.::
session.query(MyClass).filter_by(name = 'some name')
Multiple criteria may be specified as comma separated; the effect
is that they will be joined together using the :func:`.and_`
function::
session.query(MyClass).\
filter_by(name = 'some name', id = 5)
The keyword expressions are extracted from the primary
entity of the query, or the last entity that was the
target of a call to :meth:`_query.Query.join`.
.. seealso::
:meth:`_query.Query.filter` - filter on SQL expressions.
"""
from_entity = self._filter_by_zero()
if from_entity is None:
raise sa_exc.InvalidRequestError(
"Can't use filter_by when the first entity '%s' of a query "
"is not a mapped class. Please use the filter method instead, "
"or change the order of the entities in the query"
% self._query_entity_zero()
)
clauses = [
_entity_namespace_key(from_entity, key) == value
for key, value in kwargs.items()
]
return self.filter(*clauses)
@_generative
@_assertions(_no_statement_condition, _no_limit_offset)
def order_by(self, *clauses):
"""Apply one or more ORDER BY criterion to the query and return
the newly resulting :class:`_query.Query`.
All existing ORDER BY settings can be suppressed by passing
``None``.
.. seealso::
These sections describe ORDER BY in terms of :term:`2.0 style`
invocation but apply to :class:`_orm.Query` as well:
:ref:`tutorial_order_by` - in the :ref:`unified_tutorial`
:ref:`tutorial_order_by_label` - in the :ref:`unified_tutorial`
"""
if len(clauses) == 1 and (clauses[0] is None or clauses[0] is False):
self._order_by_clauses = ()
else:
criterion = tuple(
coercions.expect(roles.OrderByRole, clause)
for clause in clauses
)
# legacy vvvvvvvvvvvvvvvvvvvvvvvvvvv
if self._aliased_generation:
criterion = tuple(
[
sql_util._deep_annotate(
o, {"aliased_generation": self._aliased_generation}
)
for o in criterion
]
)
# legacy ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
self._order_by_clauses += criterion
@_generative
@_assertions(_no_statement_condition, _no_limit_offset)
def group_by(self, *clauses):
"""Apply one or more GROUP BY criterion to the query and return
the newly resulting :class:`_query.Query`.
All existing GROUP BY settings can be suppressed by
passing ``None`` - this will suppress any GROUP BY configured
on mappers as well.
.. seealso::
These sections describe GROUP BY in terms of :term:`2.0 style`
invocation but apply to :class:`_orm.Query` as well:
:ref:`tutorial_group_by_w_aggregates` - in the
:ref:`unified_tutorial`
:ref:`tutorial_order_by_label` - in the :ref:`unified_tutorial`
"""
if len(clauses) == 1 and (clauses[0] is None or clauses[0] is False):
self._group_by_clauses = ()
else:
criterion = tuple(
coercions.expect(roles.GroupByRole, clause)
for clause in clauses
)
# legacy vvvvvvvvvvvvvvvvvvvvvvvvvvv
if self._aliased_generation:
criterion = tuple(
[
sql_util._deep_annotate(
o, {"aliased_generation": self._aliased_generation}
)
for o in criterion
]
)
# legacy ^^^^^^^^^^^^^^^^^^^^^^^^^^
self._group_by_clauses += criterion
@_generative
@_assertions(_no_statement_condition, _no_limit_offset)
def having(self, criterion):
r"""Apply a HAVING criterion to the query and return the
newly resulting :class:`_query.Query`.
:meth:`_query.Query.having` is used in conjunction with
:meth:`_query.Query.group_by`.
HAVING criterion makes it possible to use filters on aggregate
functions like COUNT, SUM, AVG, MAX, and MIN, eg.::
q = session.query(User.id).\
join(User.addresses).\
group_by(User.id).\
having(func.count(Address.id) > 2)
"""
self._having_criteria += (
coercions.expect(
roles.WhereHavingRole, criterion, apply_propagate_attrs=self
),
)
def _set_op(self, expr_fn, *q):
return self._from_selectable(expr_fn(*([self] + list(q))).subquery())
def union(self, *q):
"""Produce a UNION of this Query against one or more queries.
e.g.::
q1 = sess.query(SomeClass).filter(SomeClass.foo=='bar')
q2 = sess.query(SomeClass).filter(SomeClass.bar=='foo')
q3 = q1.union(q2)
The method accepts multiple Query objects so as to control
the level of nesting. A series of ``union()`` calls such as::
x.union(y).union(z).all()
will nest on each ``union()``, and produces::
SELECT * FROM (SELECT * FROM (SELECT * FROM X UNION
SELECT * FROM y) UNION SELECT * FROM Z)
Whereas::
x.union(y, z).all()
produces::
SELECT * FROM (SELECT * FROM X UNION SELECT * FROM y UNION
SELECT * FROM Z)
Note that many database backends do not allow ORDER BY to
be rendered on a query called within UNION, EXCEPT, etc.
To disable all ORDER BY clauses including those configured
on mappers, issue ``query.order_by(None)`` - the resulting
:class:`_query.Query` object will not render ORDER BY within
its SELECT statement.
"""
return self._set_op(expression.union, *q)
def union_all(self, *q):
"""Produce a UNION ALL of this Query against one or more queries.
Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See
that method for usage examples.
"""
return self._set_op(expression.union_all, *q)
def intersect(self, *q):
"""Produce an INTERSECT of this Query against one or more queries.
Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See
that method for usage examples.
"""
return self._set_op(expression.intersect, *q)
def intersect_all(self, *q):
"""Produce an INTERSECT ALL of this Query against one or more queries.
Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See
that method for usage examples.
"""
return self._set_op(expression.intersect_all, *q)
def except_(self, *q):
"""Produce an EXCEPT of this Query against one or more queries.
Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See
that method for usage examples.
"""
return self._set_op(expression.except_, *q)
def except_all(self, *q):
"""Produce an EXCEPT ALL of this Query against one or more queries.
Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See
that method for usage examples.
"""
return self._set_op(expression.except_all, *q)
def _next_aliased_generation(self):
if "_aliased_generation_counter" not in self.__dict__:
self._aliased_generation_counter = 0
self._aliased_generation_counter += 1
return self._aliased_generation_counter
@_generative
@_assertions(_no_statement_condition, _no_limit_offset)
def join(self, target, *props, **kwargs):
r"""Create a SQL JOIN against this :class:`_query.Query`
object's criterion
and apply generatively, returning the newly resulting
:class:`_query.Query`.
**Simple Relationship Joins**
Consider a mapping between two classes ``User`` and ``Address``,
with a relationship ``User.addresses`` representing a collection
of ``Address`` objects associated with each ``User``. The most
common usage of :meth:`_query.Query.join`
is to create a JOIN along this
relationship, using the ``User.addresses`` attribute as an indicator
for how this should occur::
q = session.query(User).join(User.addresses)
Where above, the call to :meth:`_query.Query.join` along
``User.addresses`` will result in SQL approximately equivalent to::
SELECT user.id, user.name
FROM user JOIN address ON user.id = address.user_id
In the above example we refer to ``User.addresses`` as passed to
:meth:`_query.Query.join` as the "on clause", that is, it indicates
how the "ON" portion of the JOIN should be constructed.
To construct a chain of joins, multiple :meth:`_query.Query.join`
calls may be used. The relationship-bound attribute implies both
the left and right side of the join at once::
q = session.query(User).\
join(User.orders).\
join(Order.items).\
join(Item.keywords)
.. note:: as seen in the above example, **the order in which each
call to the join() method occurs is important**. Query would not,
for example, know how to join correctly if we were to specify
``User``, then ``Item``, then ``Order``, in our chain of joins; in
such a case, depending on the arguments passed, it may raise an
error that it doesn't know how to join, or it may produce invalid
SQL in which case the database will raise an error. In correct
practice, the
:meth:`_query.Query.join` method is invoked in such a way that lines
up with how we would want the JOIN clauses in SQL to be
rendered, and each call should represent a clear link from what
precedes it.
**Joins to a Target Entity or Selectable**
A second form of :meth:`_query.Query.join` allows any mapped entity or
core selectable construct as a target. In this usage,
:meth:`_query.Query.join` will attempt to create a JOIN along the
natural foreign key relationship between two entities::
q = session.query(User).join(Address)
In the above calling form, :meth:`_query.Query.join` is called upon to
create the "on clause" automatically for us. This calling form will
ultimately raise an error if either there are no foreign keys between
the two entities, or if there are multiple foreign key linkages between
the target entity and the entity or entities already present on the
left side such that creating a join requires more information. Note
that when indicating a join to a target without any ON clause, ORM
configured relationships are not taken into account.
**Joins to a Target with an ON Clause**
The third calling form allows both the target entity as well
as the ON clause to be passed explicitly. A example that includes
a SQL expression as the ON clause is as follows::
q = session.query(User).join(Address, User.id==Address.user_id)
The above form may also use a relationship-bound attribute as the
ON clause as well::
q = session.query(User).join(Address, User.addresses)
The above syntax can be useful for the case where we wish
to join to an alias of a particular target entity. If we wanted
to join to ``Address`` twice, it could be achieved using two
aliases set up using the :func:`~sqlalchemy.orm.aliased` function::
a1 = aliased(Address)
a2 = aliased(Address)
q = session.query(User).\
join(a1, User.addresses).\
join(a2, User.addresses).\
filter(a1.email_address=='ed@foo.com').\
filter(a2.email_address=='ed@bar.com')
The relationship-bound calling form can also specify a target entity
using the :meth:`_orm.PropComparator.of_type` method; a query
equivalent to the one above would be::
a1 = aliased(Address)
a2 = aliased(Address)
q = session.query(User).\
join(User.addresses.of_type(a1)).\
join(User.addresses.of_type(a2)).\
filter(a1.email_address == 'ed@foo.com').\
filter(a2.email_address == 'ed@bar.com')
**Augmenting Built-in ON Clauses**
As a substitute for providing a full custom ON condition for an
existing relationship, the :meth:`_orm.PropComparator.and_` function
may be applied to a relationship attribute to augment additional
criteria into the ON clause; the additional criteria will be combined
with the default criteria using AND::
q = session.query(User).join(
User.addresses.and_(Address.email_address != 'foo@bar.com')
)
.. versionadded:: 1.4
**Joining to Tables and Subqueries**
The target of a join may also be any table or SELECT statement,
which may be related to a target entity or not. Use the
appropriate ``.subquery()`` method in order to make a subquery
out of a query::
subq = session.query(Address).\
filter(Address.email_address == 'ed@foo.com').\
subquery()
q = session.query(User).join(
subq, User.id == subq.c.user_id
)
Joining to a subquery in terms of a specific relationship and/or
target entity may be achieved by linking the subquery to the
entity using :func:`_orm.aliased`::
subq = session.query(Address).\
filter(Address.email_address == 'ed@foo.com').\
subquery()
address_subq = aliased(Address, subq)
q = session.query(User).join(
User.addresses.of_type(address_subq)
)
**Controlling what to Join From**
In cases where the left side of the current state of
:class:`_query.Query` is not in line with what we want to join from,
the :meth:`_query.Query.select_from` method may be used::
q = session.query(Address).select_from(User).\
join(User.addresses).\
filter(User.name == 'ed')
Which will produce SQL similar to::
SELECT address.* FROM user
JOIN address ON user.id=address.user_id
WHERE user.name = :name_1
**Legacy Features of Query.join()**
.. deprecated:: 1.4 The following features are deprecated and will
be removed in SQLAlchemy 2.0.
The :meth:`_query.Query.join` method currently supports several
usage patterns and arguments that are considered to be legacy
as of SQLAlchemy 1.3. A deprecation path will follow
in the 1.4 series for the following features:
* Joining on relationship names rather than attributes::
session.query(User).join("addresses")
**Why it's legacy**: the string name does not provide enough context
for :meth:`_query.Query.join` to always know what is desired,
notably in that there is no indication of what the left side
of the join should be. This gives rise to flags like
``from_joinpoint`` as well as the ability to place several
join clauses in a single :meth:`_query.Query.join` call
which don't solve the problem fully while also
adding new calling styles that are unnecessary and expensive to
accommodate internally.
**Modern calling pattern**: Use the actual relationship,
e.g. ``User.addresses`` in the above case::
session.query(User).join(User.addresses)
* Automatic aliasing with the ``aliased=True`` flag::
session.query(Node).join(Node.children, aliased=True).\
filter(Node.name == 'some name')
**Why it's legacy**: the automatic aliasing feature of
:class:`_query.Query` is intensely complicated, both in its internal
implementation as well as in its observed behavior, and is almost
never used. It is difficult to know upon inspection where and when
its aliasing of a target entity, ``Node`` in the above case, will be
applied and when it won't, and additionally the feature has to use
very elaborate heuristics to achieve this implicit behavior.
**Modern calling pattern**: Use the :func:`_orm.aliased` construct
explicitly::
from sqlalchemy.orm import aliased
n1 = aliased(Node)
session.query(Node).join(Node.children.of_type(n1)).\
filter(n1.name == 'some name')
* Multiple joins in one call::
session.query(User).join("orders", "items")
session.query(User).join(User.orders, Order.items)
session.query(User).join(
(Order, User.orders),
(Item, Item.order_id == Order.id)
)
session.query(User).join(Order, Item)
# ... and several more forms actually
**Why it's legacy**: being able to chain multiple ON clauses in one
call to :meth:`_query.Query.join` is yet another attempt to solve
the problem of being able to specify what entity to join from,
and is the source of a large variety of potential calling patterns
that are internally expensive and complicated to parse and
accommodate.
**Modern calling pattern**: Use relationship-bound attributes
or SQL-oriented ON clauses within separate calls, so that
each call to :meth:`_query.Query.join` knows what the left
side should be::
session.query(User).join(User.orders).join(
Item, Item.order_id == Order.id)
:param \*props: Incoming arguments for :meth:`_query.Query.join`,
the props collection in modern use should be considered to be a one
or two argument form, either as a single "target" entity or ORM
attribute-bound relationship, or as a target entity plus an "on
clause" which may be a SQL expression or ORM attribute-bound
relationship.
:param isouter=False: If True, the join used will be a left outer join,
just as if the :meth:`_query.Query.outerjoin` method were called.
:param full=False: render FULL OUTER JOIN; implies ``isouter``.
.. versionadded:: 1.1
:param from_joinpoint=False: When using ``aliased=True``, a setting
of True here will cause the join to be from the most recent
joined target, rather than starting back from the original
FROM clauses of the query.
.. note:: This flag is considered legacy.
:param aliased=False: If True, indicate that the JOIN target should be
anonymously aliased. Subsequent calls to :meth:`_query.Query.filter`
and similar will adapt the incoming criterion to the target
alias, until :meth:`_query.Query.reset_joinpoint` is called.
.. note:: This flag is considered legacy.
.. seealso::
:ref:`ormtutorial_joins` in the ORM tutorial.
:ref:`inheritance_toplevel` for details on how
:meth:`_query.Query.join` is used for inheritance relationships.
:func:`_orm.join` - a standalone ORM-level join function,
used internally by :meth:`_query.Query.join`, which in previous
SQLAlchemy versions was the primary ORM-level joining interface.
"""
aliased, from_joinpoint, isouter, full = (
kwargs.pop("aliased", False),
kwargs.pop("from_joinpoint", False),
kwargs.pop("isouter", False),
kwargs.pop("full", False),
)
if aliased or from_joinpoint:
util.warn_deprecated_20(
"The ``aliased`` and ``from_joinpoint`` keyword arguments "
"to Query.join() are deprecated and will be removed "
"in SQLAlchemy 2.0."
)
if kwargs:
raise TypeError(
"unknown arguments: %s" % ", ".join(sorted(kwargs))
)
# legacy vvvvvvvvvvvvvvvvvvvvvvvvvvv
if not from_joinpoint:
self._last_joined_entity = None
self._aliased_generation = None
# legacy ^^^^^^^^^^^^^^^^^^^^^^^^^^^
if props:
onclause, legacy = props[0], props[1:]
else:
onclause = legacy = None
if not legacy and onclause is None and not isinstance(target, tuple):
# non legacy argument form
_props = [(target,)]
elif (
not legacy
and isinstance(
target,
(
expression.Selectable,
type,
AliasedClass,
types.FunctionType,
),
)
and isinstance(
onclause,
(
elements.ColumnElement,
str,
interfaces.PropComparator,
types.FunctionType,
),
)
):
# non legacy argument form
_props = [(target, onclause)]
else:
# legacy forms. more time consuming :)
_props = []
_single = []
for prop in (target,) + props:
if isinstance(prop, tuple):
util.warn_deprecated_20(
"Query.join() will no longer accept tuples as "
"arguments in SQLAlchemy 2.0."
)
if _single:
_props.extend((_s,) for _s in _single)
_single = []
# this checks for an extremely ancient calling form of
# reversed tuples.
if isinstance(prop[0], (str, interfaces.PropComparator)):
prop = (prop[1], prop[0])
_props.append(prop)
else:
_single.append(prop)
if _single:
_props.extend((_s,) for _s in _single)
# legacy vvvvvvvvvvvvvvvvvvvvvvvvvvv
if aliased:
self._aliased_generation = self._next_aliased_generation()
if self._aliased_generation:
_props = [
(
prop[0],
sql_util._deep_annotate(
prop[1],
{"aliased_generation": self._aliased_generation},
)
if isinstance(prop[1], expression.ClauseElement)
else prop[1],
)
if len(prop) == 2
else prop
for prop in _props
]
# legacy ^^^^^^^^^^^^^^^^^^^^^^^^^^^
joins_to_add = tuple(
(
coercions.expect(
roles.JoinTargetRole,
prop[0],
legacy=True,
apply_propagate_attrs=self,
),
(
coercions.expect(roles.OnClauseRole, prop[1], legacy=True)
# if not isinstance(prop[1], str)
# else prop[1]
)
if len(prop) == 2
else None,
None,
{
"isouter": isouter,
"aliased": aliased,
"from_joinpoint": True if i > 0 else from_joinpoint,
"full": full,
"aliased_generation": self._aliased_generation,
},
)
for i, prop in enumerate(_props)
)
if len(joins_to_add) > 1:
util.warn_deprecated_20(
"Passing a chain of multiple join conditions to Query.join() "
"is deprecated and will be removed in SQLAlchemy 2.0. "
"Please use individual join() calls per relationship."
)
self._legacy_setup_joins += joins_to_add
self.__dict__.pop("_last_joined_entity", None)
def outerjoin(self, target, *props, **kwargs):
"""Create a left outer join against this ``Query`` object's criterion
and apply generatively, returning the newly resulting ``Query``.
Usage is the same as the ``join()`` method.
"""
kwargs["isouter"] = True
return self.join(target, *props, **kwargs)
@_generative
@_assertions(_no_statement_condition)
def reset_joinpoint(self):
"""Return a new :class:`.Query`, where the "join point" has
been reset back to the base FROM entities of the query.
This method is usually used in conjunction with the
``aliased=True`` feature of the :meth:`~.Query.join`
method. See the example in :meth:`~.Query.join` for how
this is used.
"""
self._last_joined_entity = None
self._aliased_generation = None
@_generative
@_assertions(_no_clauseelement_condition)
def select_from(self, *from_obj):
r"""Set the FROM clause of this :class:`.Query` explicitly.
:meth:`.Query.select_from` is often used in conjunction with
:meth:`.Query.join` in order to control which entity is selected
from on the "left" side of the join.
The entity or selectable object here effectively replaces the
"left edge" of any calls to :meth:`~.Query.join`, when no
joinpoint is otherwise established - usually, the default "join
point" is the leftmost entity in the :class:`~.Query` object's
list of entities to be selected.
A typical example::
q = session.query(Address).select_from(User).\
join(User.addresses).\
filter(User.name == 'ed')
Which produces SQL equivalent to::
SELECT address.* FROM user
JOIN address ON user.id=address.user_id
WHERE user.name = :name_1
:param \*from_obj: collection of one or more entities to apply
to the FROM clause. Entities can be mapped classes,
:class:`.AliasedClass` objects, :class:`.Mapper` objects
as well as core :class:`.FromClause` elements like subqueries.
.. versionchanged:: 0.9
This method no longer applies the given FROM object
to be the selectable from which matching entities
select from; the :meth:`.select_entity_from` method
now accomplishes this. See that method for a description
of this behavior.
.. seealso::
:meth:`~.Query.join`
:meth:`.Query.select_entity_from`
"""
self._set_select_from(from_obj, False)
@util.deprecated_20(
":meth:`_orm.Query.select_entity_from`",
alternative="Use the :func:`_orm.aliased` construct instead",
)
@_generative
@_assertions(_no_clauseelement_condition)
def select_entity_from(self, from_obj):
r"""Set the FROM clause of this :class:`_query.Query` to a
core selectable, applying it as a replacement FROM clause
for corresponding mapped entities.
The :meth:`_query.Query.select_entity_from`
method supplies an alternative
approach to the use case of applying an :func:`.aliased` construct
explicitly throughout a query. Instead of referring to the
:func:`.aliased` construct explicitly,
:meth:`_query.Query.select_entity_from` automatically *adapts* all
occurrences of the entity to the target selectable.
Given a case for :func:`.aliased` such as selecting ``User``
objects from a SELECT statement::
select_stmt = select(User).where(User.id == 7)
user_alias = aliased(User, select_stmt)
q = session.query(user_alias).\
filter(user_alias.name == 'ed')
Above, we apply the ``user_alias`` object explicitly throughout the
query. When it's not feasible for ``user_alias`` to be referenced
explicitly in many places, :meth:`_query.Query.select_entity_from`
may be
used at the start of the query to adapt the existing ``User`` entity::
q = session.query(User).\
select_entity_from(select_stmt.subquery()).\
filter(User.name == 'ed')
Above, the generated SQL will show that the ``User`` entity is
adapted to our statement, even in the case of the WHERE clause:
.. sourcecode:: sql
SELECT anon_1.id AS anon_1_id, anon_1.name AS anon_1_name
FROM (SELECT "user".id AS id, "user".name AS name
FROM "user"
WHERE "user".id = :id_1) AS anon_1
WHERE anon_1.name = :name_1
The :meth:`_query.Query.select_entity_from` method is similar to the
:meth:`_query.Query.select_from` method,
in that it sets the FROM clause
of the query. The difference is that it additionally applies
adaptation to the other parts of the query that refer to the
primary entity. If above we had used :meth:`_query.Query.select_from`
instead, the SQL generated would have been:
.. sourcecode:: sql
-- uses plain select_from(), not select_entity_from()
SELECT "user".id AS user_id, "user".name AS user_name
FROM "user", (SELECT "user".id AS id, "user".name AS name
FROM "user"
WHERE "user".id = :id_1) AS anon_1
WHERE "user".name = :name_1
To supply textual SQL to the :meth:`_query.Query.select_entity_from`
method,
we can make use of the :func:`_expression.text` construct. However,
the
:func:`_expression.text`
construct needs to be aligned with the columns of our
entity, which is achieved by making use of the
:meth:`_expression.TextClause.columns` method::
text_stmt = text("select id, name from user").columns(
User.id, User.name).subquery()
q = session.query(User).select_entity_from(text_stmt)
:meth:`_query.Query.select_entity_from` itself accepts an
:func:`.aliased`
object, so that the special options of :func:`.aliased` such as
:paramref:`.aliased.adapt_on_names` may be used within the
scope of the :meth:`_query.Query.select_entity_from`
method's adaptation
services. Suppose
a view ``user_view`` also returns rows from ``user``. If
we reflect this view into a :class:`_schema.Table`, this view has no
relationship to the :class:`_schema.Table` to which we are mapped,
however
we can use name matching to select from it::
user_view = Table('user_view', metadata,
autoload_with=engine)
user_view_alias = aliased(
User, user_view, adapt_on_names=True)
q = session.query(User).\
select_entity_from(user_view_alias).\
order_by(User.name)
.. versionchanged:: 1.1.7 The :meth:`_query.Query.select_entity_from`
method now accepts an :func:`.aliased` object as an alternative
to a :class:`_expression.FromClause` object.
:param from_obj: a :class:`_expression.FromClause`
object that will replace
the FROM clause of this :class:`_query.Query`.
It also may be an instance
of :func:`.aliased`.
.. seealso::
:meth:`_query.Query.select_from`
"""
self._set_select_from([from_obj], True)
self._compile_options += {"_enable_single_crit": False}
def __getitem__(self, item):
return orm_util._getitem(
self,
item,
allow_negative=not self.session or not self.session.future,
)
@_generative
@_assertions(_no_statement_condition)
def slice(self, start, stop):
"""Computes the "slice" of the :class:`_query.Query` represented by
the given indices and returns the resulting :class:`_query.Query`.
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, ::
session.query(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)
.. seealso::
:meth:`_query.Query.limit`
:meth:`_query.Query.offset`
"""
self._limit_clause, self._offset_clause = sql_util._make_slice(
self._limit_clause, self._offset_clause, start, stop
)
@_generative
@_assertions(_no_statement_condition)
def limit(self, limit):
"""Apply a ``LIMIT`` to the query and return the newly resulting
``Query``.
"""
self._limit_clause = sql_util._offset_or_limit_clause(limit)
@_generative
@_assertions(_no_statement_condition)
def offset(self, offset):
"""Apply an ``OFFSET`` to the query and return the newly resulting
``Query``.
"""
self._offset_clause = sql_util._offset_or_limit_clause(offset)
@_generative
@_assertions(_no_statement_condition)
def distinct(self, *expr):
r"""Apply a ``DISTINCT`` to the query and return the newly resulting
``Query``.
.. note::
The ORM-level :meth:`.distinct` call includes logic that will
automatically add columns from the ORDER BY of the query to the
columns clause of the SELECT statement, to satisfy the common need
of the database backend that ORDER BY columns be part of the SELECT
list when DISTINCT is used. These columns *are not* added to the
list of columns actually fetched by the :class:`_query.Query`,
however,
so would not affect results. The columns are passed through when
using the :attr:`_query.Query.statement` accessor, however.
.. deprecated:: 2.0 This logic is deprecated and will be removed
in SQLAlchemy 2.0. See :ref:`migration_20_query_distinct`
for a description of this use case in 2.0.
:param \*expr: optional column expressions. When present,
the PostgreSQL dialect will render a ``DISTINCT ON (<expressions>)``
construct.
.. 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) for e in expr
)
else:
self._distinct = True
def all(self):
"""Return the results represented by this :class:`_query.Query`
as a list.
This results in an execution of the underlying SQL statement.
.. warning:: The :class:`_query.Query` object,
when asked to return either
a sequence or iterator that consists of full ORM-mapped entities,
will **deduplicate entries based on primary key**. See the FAQ for
more details.
.. seealso::
:ref:`faq_query_deduplicating`
"""
return self._iter().all()
@_generative
@_assertions(_no_clauseelement_condition)
def from_statement(self, statement):
"""Execute the given SELECT statement and return results.
This method bypasses all internal statement compilation, and the
statement is executed without modification.
The statement is typically either a :func:`_expression.text`
or :func:`_expression.select` construct, and should return the set
of columns
appropriate to the entity class represented by this
:class:`_query.Query`.
.. seealso::
:ref:`orm_tutorial_literal_sql` - usage examples in the
ORM tutorial
"""
statement = coercions.expect(
roles.SelectStatementRole, statement, apply_propagate_attrs=self
)
self._statement = statement
def first(self):
"""Return the first result of this ``Query`` or
None if the result doesn't contain any row.
first() applies a limit of one within the generated SQL, so that
only one primary entity row is generated on the server side
(note this may consist of multiple result rows if join-loaded
collections are present).
Calling :meth:`_query.Query.first`
results in an execution of the underlying
query.
.. seealso::
:meth:`_query.Query.one`
:meth:`_query.Query.one_or_none`
"""
# replicates limit(1) behavior
if self._statement is not None:
return self._iter().first()
else:
return self.limit(1)._iter().first()
def one_or_none(self):
"""Return at most one result or raise an exception.
Returns ``None`` if the query selects
no rows. Raises ``sqlalchemy.orm.exc.MultipleResultsFound``
if multiple object identities are returned, or if multiple
rows are returned for a query that returns only scalar values
as opposed to full identity-mapped entities.
Calling :meth:`_query.Query.one_or_none`
results in an execution of the
underlying query.
.. versionadded:: 1.0.9
Added :meth:`_query.Query.one_or_none`
.. seealso::
:meth:`_query.Query.first`
:meth:`_query.Query.one`
"""
return self._iter().one_or_none()
def one(self):
"""Return exactly one result or raise an exception.
Raises ``sqlalchemy.orm.exc.NoResultFound`` if the query selects
no rows. Raises ``sqlalchemy.orm.exc.MultipleResultsFound``
if multiple object identities are returned, or if multiple
rows are returned for a query that returns only scalar values
as opposed to full identity-mapped entities.
Calling :meth:`.one` results in an execution of the underlying query.
.. seealso::
:meth:`_query.Query.first`
:meth:`_query.Query.one_or_none`
"""
return self._iter().one()
def scalar(self):
"""Return the first element of the first result or None
if no rows present. If multiple rows are returned,
raises MultipleResultsFound.
>>> session.query(Item).scalar()
<Item>
>>> session.query(Item.id).scalar()
1
>>> session.query(Item.id).filter(Item.id < 0).scalar()
None
>>> session.query(Item.id, Item.name).scalar()
1
>>> session.query(func.count(Parent.id)).scalar()
20
This results in an execution of the underlying query.
"""
# TODO: not sure why we can't use result.scalar() here
try:
ret = self.one()
if not isinstance(ret, collections_abc.Sequence):
return ret
return ret[0]
except orm_exc.NoResultFound:
return None
def __iter__(self):
return self._iter().__iter__()
def _iter(self):
# new style execution.
params = self._params
statement = self._statement_20()
result = self.session.execute(
statement,
params,
execution_options={"_sa_orm_load_options": self.load_options},
)
# legacy: automatically set scalars, unique
if result._attributes.get("is_single_entity", False):
result = result.scalars()
if (
result._attributes.get("filtered", False)
and not self.load_options._yield_per
):
result = result.unique()
return result
def __str__(self):
statement = self._statement_20()
try:
bind = (
self._get_bind_args(statement, self.session.get_bind)
if self.session
else None
)
except sa_exc.UnboundExecutionError:
bind = None
return str(statement.compile(bind))
def _get_bind_args(self, statement, fn, **kw):
return fn(clause=statement, **kw)
@property
def column_descriptions(self):
"""Return metadata about the columns which would be
returned by this :class:`_query.Query`.
Format is a list of dictionaries::
user_alias = aliased(User, name='user2')
q = sess.query(User, User.id, user_alias)
# this expression:
q.column_descriptions
# would return:
[
{
'name':'User',
'type':User,
'aliased':False,
'expr':User,
'entity': User
},
{
'name':'id',
'type':Integer(),
'aliased':False,
'expr':User.id,
'entity': User
},
{
'name':'user2',
'type':User,
'aliased':True,
'expr':user_alias,
'entity': user_alias
}
]
"""
return _column_descriptions(self, legacy=True)
def instances(self, result_proxy, context=None):
"""Return an ORM result given a :class:`_engine.CursorResult` and
:class:`.QueryContext`.
"""
if context is None:
util.warn_deprecated(
"Using the Query.instances() method without a context "
"is deprecated and will be disallowed in a future release. "
"Please make use of :meth:`_query.Query.from_statement` "
"for linking ORM results to arbitrary select constructs.",
version="1.4",
)
compile_state = self._compile_state(for_statement=False)
context = QueryContext(
compile_state,
compile_state.statement,
self._params,
self.session,
self.load_options,
)
result = loading.instances(result_proxy, context)
# legacy: automatically set scalars, unique
if result._attributes.get("is_single_entity", False):
result = result.scalars()
if result._attributes.get("filtered", False):
result = result.unique()
return result
def merge_result(self, iterator, load=True):
"""Merge a result into this :class:`_query.Query` object's Session.
Given an iterator returned by a :class:`_query.Query`
of the same structure
as this one, return an identical iterator of results, with all mapped
instances merged into the session using :meth:`.Session.merge`. This
is an optimized method which will merge all mapped instances,
preserving the structure of the result rows and unmapped columns with
less method overhead than that of calling :meth:`.Session.merge`
explicitly for each value.
The structure of the results is determined based on the column list of
this :class:`_query.Query` - if these do not correspond,
unchecked errors
will occur.
The 'load' argument is the same as that of :meth:`.Session.merge`.
For an example of how :meth:`_query.Query.merge_result` is used, see
the source code for the example :ref:`examples_caching`, where
:meth:`_query.Query.merge_result` is used to efficiently restore state
from a cache back into a target :class:`.Session`.
"""
return loading.merge_result(self, iterator, load)
def exists(self):
"""A convenience method that turns a query into an EXISTS subquery
of the form EXISTS (SELECT 1 FROM ... WHERE ...).
e.g.::
q = session.query(User).filter(User.name == 'fred')
session.query(q.exists())
Producing SQL similar to::
SELECT EXISTS (
SELECT 1 FROM users WHERE users.name = :name_1
) AS anon_1
The EXISTS construct is usually used in the WHERE clause::
session.query(User.id).filter(q.exists()).scalar()
Note that some databases such as SQL Server don't allow an
EXISTS expression to be present in the columns clause of a
SELECT. To select a simple boolean value based on the exists
as a WHERE, use :func:`.literal`::
from sqlalchemy import literal
session.query(literal(True)).filter(q.exists()).scalar()
"""
# .add_columns() for the case that we are a query().select_from(X),
# so that ".statement" can be produced (#2995) but also without
# omitting the FROM clause from a query(X) (#2818);
# .with_only_columns() after we have a core select() so that
# we get just "SELECT 1" without any entities.
inner = (
self.enable_eagerloads(False)
.add_columns(sql.literal_column("1"))
.set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)
.statement.with_only_columns(1)
)
ezero = self._entity_from_pre_ent_zero()
if ezero is not None:
inner = inner.select_from(ezero)
return sql.exists(inner)
def count(self):
r"""Return a count of rows this the SQL formed by this :class:`Query`
would return.
This generates the SQL for this Query as follows::
SELECT count(1) AS count_1 FROM (
SELECT <rest of query follows...>
) AS anon_1
The above SQL returns a single row, which is the aggregate value
of the count function; the :meth:`_query.Query.count`
method then returns
that single integer value.
.. warning::
It is important to note that the value returned by
count() is **not the same as the number of ORM objects that this
Query would return from a method such as the .all() method**.
The :class:`_query.Query` object,
when asked to return full entities,
will **deduplicate entries based on primary key**, meaning if the
same primary key value would appear in the results more than once,
only one object of that primary key would be present. This does
not apply to a query that is against individual columns.
.. seealso::
:ref:`faq_query_deduplicating`
:ref:`orm_tutorial_query_returning`
For fine grained control over specific columns to count, to skip the
usage of a subquery or otherwise control of the FROM clause, or to use
other aggregate functions, use :attr:`~sqlalchemy.sql.expression.func`
expressions in conjunction with :meth:`~.Session.query`, i.e.::
from sqlalchemy import func
# count User records, without
# using a subquery.
session.query(func.count(User.id))
# return count of user "id" grouped
# by "name"
session.query(func.count(User.id)).\
group_by(User.name)
from sqlalchemy import distinct
# count distinct "name" values
session.query(func.count(distinct(User.name)))
"""
col = sql.func.count(sql.literal_column("*"))
return self._from_self(col).enable_eagerloads(False).scalar()
def delete(self, synchronize_session="evaluate"):
r"""Perform a DELETE with an arbitrary WHERE clause.
Deletes rows matched by this query from the database.
E.g.::
sess.query(User).filter(User.age == 25).\
delete(synchronize_session=False)
sess.query(User).filter(User.age == 25).\
delete(synchronize_session='evaluate')
.. warning::
See the section :ref:`orm_expression_update_delete` for important
caveats and warnings, including limitations when using bulk UPDATE
and DELETE with mapper inheritance configurations.
:param synchronize_session: chooses the strategy to update the
attributes on objects in the session. See the section
:ref:`orm_expression_update_delete` for a discussion of these
strategies.
:return: the count of rows matched as returned by the database's
"row count" feature.
.. seealso::
:ref:`orm_expression_update_delete`
"""
bulk_del = BulkDelete(self)
if self.dispatch.before_compile_delete:
for fn in self.dispatch.before_compile_delete:
new_query = fn(bulk_del.query, bulk_del)
if new_query is not None:
bulk_del.query = new_query
self = bulk_del.query
delete_ = sql.delete(*self._raw_columns)
delete_._where_criteria = self._where_criteria
result = self.session.execute(
delete_,
self._params,
execution_options={"synchronize_session": synchronize_session},
)
bulk_del.result = result
self.session.dispatch.after_bulk_delete(bulk_del)
result.close()
return result.rowcount
def update(self, values, synchronize_session="evaluate", update_args=None):
r"""Perform an UPDATE with an arbitrary WHERE clause.
Updates rows matched by this query in the database.
E.g.::
sess.query(User).filter(User.age == 25).\
update({User.age: User.age - 10}, synchronize_session=False)
sess.query(User).filter(User.age == 25).\
update({"age": User.age - 10}, synchronize_session='evaluate')
.. warning::
See the section :ref:`orm_expression_update_delete` for important
caveats and warnings, including limitations when using arbitrary
UPDATE and DELETE with mapper inheritance configurations.
:param values: a dictionary with attributes names, or alternatively
mapped attributes or SQL expressions, as keys, and literal
values or sql expressions as values. If :ref:`parameter-ordered
mode <updates_order_parameters>` is desired, the values can be
passed as a list of 2-tuples;
this requires that the
:paramref:`~sqlalchemy.sql.expression.update.preserve_parameter_order`
flag is passed to the :paramref:`.Query.update.update_args` dictionary
as well.
:param synchronize_session: chooses the strategy to update the
attributes on objects in the session. See the section
:ref:`orm_expression_update_delete` for a discussion of these
strategies.
:param update_args: Optional dictionary, if present will be passed
to the underlying :func:`_expression.update`
construct as the ``**kw`` for
the object. May be used to pass dialect-specific arguments such
as ``mysql_limit``, as well as other special arguments such as
:paramref:`~sqlalchemy.sql.expression.update.preserve_parameter_order`.
:return: the count of rows matched as returned by the database's
"row count" feature.
.. seealso::
:ref:`orm_expression_update_delete`
"""
update_args = update_args or {}
bulk_ud = BulkUpdate(self, values, update_args)
if self.dispatch.before_compile_update:
for fn in self.dispatch.before_compile_update:
new_query = fn(bulk_ud.query, bulk_ud)
if new_query is not None:
bulk_ud.query = new_query
self = bulk_ud.query
upd = sql.update(*self._raw_columns)
ppo = update_args.pop("preserve_parameter_order", False)
if ppo:
upd = upd.ordered_values(*values)
else:
upd = upd.values(values)
if update_args:
upd = upd.with_dialect_options(**update_args)
upd._where_criteria = self._where_criteria
result = self.session.execute(
upd,
self._params,
execution_options={"synchronize_session": synchronize_session},
)
bulk_ud.result = result
self.session.dispatch.after_bulk_update(bulk_ud)
result.close()
return result.rowcount
def _compile_state(self, for_statement=False, **kw):
"""Create an out-of-compiler ORMCompileState object.
The ORMCompileState object is normally created directly as a result
of the SQLCompiler.process() method being handed a Select()
or FromStatement() object that uses the "orm" plugin. This method
provides a means of creating this ORMCompileState object directly
without using the compiler.
This method is used only for deprecated cases, which include
the .from_self() method for a Query that has multiple levels
of .from_self() in use, as well as the instances() method. It is
also used within the test suite to generate ORMCompileState objects
for test purposes.
"""
stmt = self._statement_20(for_statement=for_statement, **kw)
assert for_statement == stmt._compile_options._for_statement
# this chooses between ORMFromStatementCompileState and
# ORMSelectCompileState. We could also base this on
# query._statement is not None as we have the ORM Query here
# however this is the more general path.
compile_state_cls = ORMCompileState._get_plugin_class_for_plugin(
stmt, "orm"
)
return compile_state_cls.create_for_statement(stmt, None)
def _compile_context(self, for_statement=False):
compile_state = self._compile_state(for_statement=for_statement)
context = QueryContext(
compile_state,
compile_state.statement,
self._params,
self.session,
self.load_options,
)
return context
class FromStatement(GroupedElement, SelectBase, Executable):
"""Core construct that represents a load of ORM objects from a finished
select or text construct.
"""
__visit_name__ = "orm_from_statement"
_compile_options = ORMFromStatementCompileState.default_compile_options
_compile_state_factory = ORMFromStatementCompileState.create_for_statement
_for_update_arg = None
_traverse_internals = [
("_raw_columns", InternalTraversal.dp_clauseelement_list),
("element", InternalTraversal.dp_clauseelement),
] + Executable._executable_traverse_internals
_cache_key_traversal = _traverse_internals + [
("_compile_options", InternalTraversal.dp_has_cache_key)
]
def __init__(self, entities, element):
self._raw_columns = [
coercions.expect(
roles.ColumnsClauseRole,
ent,
apply_propagate_attrs=self,
post_inspect=True,
)
for ent in util.to_list(entities)
]
self.element = element
def get_label_style(self):
return self._label_style
def set_label_style(self, label_style):
return SelectStatementGrouping(
self.element.set_label_style(label_style)
)
@property
def _label_style(self):
return self.element._label_style
def _compiler_dispatch(self, compiler, **kw):
"""provide a fixed _compiler_dispatch method.
This is roughly similar to using the sqlalchemy.ext.compiler
``@compiles`` extension.
"""
compile_state = self._compile_state_factory(self, compiler, **kw)
toplevel = not compiler.stack
if toplevel:
compiler.compile_state = compile_state
return compiler.process(compile_state.statement, **kw)
def _ensure_disambiguated_names(self):
return self
def get_children(self, **kw):
for elem in itertools.chain.from_iterable(
element._from_objects for element in self._raw_columns
):
yield elem
for elem in super(FromStatement, self).get_children(**kw):
yield elem
@property
def _returning(self):
return self.element._returning if self.element.is_dml else None
@property
def _inline(self):
return self.element._inline if self.element.is_dml else None
class AliasOption(interfaces.LoaderOption):
@util.deprecated(
"1.4",
"The :class:`.AliasOption` is not necessary "
"for entities to be matched up to a query that is established "
"via :meth:`.Query.from_statement` and now does nothing.",
)
def __init__(self, alias):
r"""Return a :class:`.MapperOption` that will indicate to the
:class:`_query.Query`
that the main table has been aliased.
"""
def process_compile_state(self, compile_state):
pass
class BulkUD(object):
"""State used for the orm.Query version of update() / delete().
This object is now specific to Query only.
"""
def __init__(self, query):
self.query = query.enable_eagerloads(False)
self._validate_query_state()
self.mapper = self.query._entity_from_pre_ent_zero()
def _validate_query_state(self):
for attr, methname, notset, op in (
("_limit_clause", "limit()", None, operator.is_),
("_offset_clause", "offset()", None, operator.is_),
("_order_by_clauses", "order_by()", (), operator.eq),
("_group_by_clauses", "group_by()", (), operator.eq),
("_distinct", "distinct()", False, operator.is_),
(
"_from_obj",
"join(), outerjoin(), select_from(), or from_self()",
(),
operator.eq,
),
(
"_legacy_setup_joins",
"join(), outerjoin(), select_from(), or from_self()",
(),
operator.eq,
),
):
if not op(getattr(self.query, attr), notset):
raise sa_exc.InvalidRequestError(
"Can't call Query.update() or Query.delete() "
"when %s has been called" % (methname,)
)
@property
def session(self):
return self.query.session
class BulkUpdate(BulkUD):
"""BulkUD which handles UPDATEs."""
def __init__(self, query, values, update_kwargs):
super(BulkUpdate, self).__init__(query)
self.values = values
self.update_kwargs = update_kwargs
class BulkDelete(BulkUD):
"""BulkUD which handles DELETEs."""
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