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# orm/query.py
# Copyright (C) 2005-2016 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` class, the central
construct used by the ORM to construct database queries.
The :class:`.Query` class should not be confused with the
:class:`.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.
"""
from itertools import chain
from . import (
attributes, interfaces, object_mapper, persistence,
exc as orm_exc, loading
)
from .base import _entity_descriptor, _is_aliased_class, \
_is_mapped_class, _orm_columns, _generative, InspectionAttr
from .path_registry import PathRegistry
from .util import (
AliasedClass, ORMAdapter, join as orm_join, with_parent, aliased
)
from .. import sql, util, log, exc as sa_exc, inspect, inspection
from ..sql.expression import _interpret_as_from
from ..sql import (
util as sql_util,
expression, visitors
)
from ..sql.base import ColumnCollection
from . import properties
__all__ = ['Query', 'QueryContext', 'aliased']
_path_registry = PathRegistry.root
@inspection._self_inspects
@log.class_logger
class Query(object):
"""ORM-level SQL construction object.
:class:`.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` object, a copy of the former with additional
criteria and options associated with it.
:class:`.Query` objects are normally initially generated using the
:meth:`~.Session.query` method of :class:`.Session`. For a full
walkthrough of :class:`.Query` usage, see the
:ref:`ormtutorial_toplevel`.
"""
_enable_eagerloads = True
_enable_assertions = True
_with_labels = False
_criterion = None
_yield_per = None
_order_by = False
_group_by = False
_having = None
_distinct = False
_prefixes = None
_suffixes = None
_offset = None
_limit = None
_for_update_arg = None
_statement = None
_correlate = frozenset()
_populate_existing = False
_invoke_all_eagers = True
_version_check = False
_autoflush = True
_only_load_props = None
_refresh_state = None
_from_obj = ()
_join_entities = ()
_select_from_entity = None
_mapper_adapter_map = {}
_filter_aliases = None
_from_obj_alias = None
_joinpath = _joinpoint = util.immutabledict()
_execution_options = util.immutabledict()
_params = util.immutabledict()
_attributes = util.immutabledict()
_with_options = ()
_with_hints = ()
_enable_single_crit = True
_orm_only_adapt = True
_orm_only_from_obj_alias = True
_current_path = _path_registry
def __init__(self, entities, session=None):
self.session = session
self._polymorphic_adapters = {}
self._set_entities(entities)
def _set_entities(self, entities, entity_wrapper=None):
if entity_wrapper is None:
entity_wrapper = _QueryEntity
self._entities = []
self._primary_entity = None
for ent in util.to_list(entities):
entity_wrapper(self, ent)
self._set_entity_selectables(self._entities)
def _set_entity_selectables(self, entities):
self._mapper_adapter_map = d = self._mapper_adapter_map.copy()
for ent in entities:
for entity in ent.entities:
if entity not in d:
ext_info = inspect(entity)
if not ext_info.is_aliased_class and \
ext_info.mapper.with_polymorphic:
if ext_info.mapper.mapped_table not in \
self._polymorphic_adapters:
self._mapper_loads_polymorphically_with(
ext_info.mapper,
sql_util.ColumnAdapter(
ext_info.selectable,
ext_info.mapper._equivalent_columns
)
)
aliased_adapter = None
elif ext_info.is_aliased_class:
aliased_adapter = ext_info._adapter
else:
aliased_adapter = None
d[entity] = (
ext_info,
aliased_adapter
)
ent.setup_entity(*d[entity])
def _mapper_loads_polymorphically_with(self, mapper, adapter):
for m2 in mapper._with_polymorphic_mappers or [mapper]:
self._polymorphic_adapters[m2] = adapter
for m in m2.iterate_to_root():
self._polymorphic_adapters[m.local_table] = adapter
def _set_select_from(self, obj, set_base_alias):
fa = []
select_from_alias = None
for from_obj in obj:
info = inspect(from_obj)
if hasattr(info, 'mapper') and \
(info.is_mapper or info.is_aliased_class):
self._select_from_entity = from_obj
if set_base_alias:
raise sa_exc.ArgumentError(
"A selectable (FromClause) instance is "
"expected when the base alias is being set.")
fa.append(info.selectable)
elif not info.is_selectable:
raise sa_exc.ArgumentError(
"argument is not a mapped class, mapper, "
"aliased(), or FromClause instance.")
else:
if isinstance(from_obj, expression.SelectBase):
from_obj = from_obj.alias()
if set_base_alias:
select_from_alias = from_obj
fa.append(from_obj)
self._from_obj = tuple(fa)
if set_base_alias and \
len(self._from_obj) == 1 and \
isinstance(select_from_alias, expression.Alias):
equivs = self.__all_equivs()
self._from_obj_alias = sql_util.ColumnAdapter(
self._from_obj[0], equivs)
def _reset_polymorphic_adapter(self, mapper):
for m2 in mapper._with_polymorphic_mappers:
self._polymorphic_adapters.pop(m2, None)
for m in m2.iterate_to_root():
self._polymorphic_adapters.pop(m.local_table, None)
def _adapt_polymorphic_element(self, element):
if "parententity" in element._annotations:
search = element._annotations['parententity']
alias = self._polymorphic_adapters.get(search, None)
if alias:
return alias.adapt_clause(element)
if isinstance(element, expression.FromClause):
search = element
elif hasattr(element, 'table'):
search = element.table
else:
return None
alias = self._polymorphic_adapters.get(search, None)
if alias:
return alias.adapt_clause(element)
def _adapt_col_list(self, cols):
return [
self._adapt_clause(
expression._literal_as_label_reference(o),
True, True)
for o in cols
]
@_generative()
def _adapt_all_clauses(self):
self._orm_only_adapt = False
def _adapt_clause(self, clause, as_filter, orm_only):
"""Adapt incoming clauses to transformations which
have been applied within this query."""
adapters = []
# do we adapt all expression elements or only those
# tagged as 'ORM' constructs ?
if not self._orm_only_adapt:
orm_only = False
if as_filter and self._filter_aliases:
for fa in self._filter_aliases._visitor_iterator:
adapters.append(
(
orm_only, fa.replace
)
)
if self._from_obj_alias:
# for the "from obj" alias, apply extra rule to the
# 'ORM only' check, if this query were generated from a
# subquery of itself, i.e. _from_selectable(), apply adaption
# to all SQL constructs.
adapters.append(
(
orm_only if self._orm_only_from_obj_alias else False,
self._from_obj_alias.replace
)
)
if self._polymorphic_adapters:
adapters.append(
(
orm_only, self._adapt_polymorphic_element
)
)
if not adapters:
return clause
def replace(elem):
for _orm_only, adapter in adapters:
# if 'orm only', look for ORM annotations
# in the element before adapting.
if not _orm_only or \
'_orm_adapt' in elem._annotations or \
"parententity" in elem._annotations:
e = adapter(elem)
if e is not None:
return e
return visitors.replacement_traverse(
clause,
{},
replace
)
def _entity_zero(self):
return self._entities[0]
def _mapper_zero(self):
# TODO: self._select_from_entity is not a mapper
# so this method is misnamed
return self._select_from_entity \
if self._select_from_entity is not None \
else self._entity_zero().entity_zero
@property
def _mapper_entities(self):
for ent in self._entities:
if isinstance(ent, _MapperEntity):
yield ent
def _joinpoint_zero(self):
return self._joinpoint.get(
'_joinpoint_entity',
self._mapper_zero()
)
def _bind_mapper(self):
ezero = self._mapper_zero()
if ezero is not None:
insp = inspect(ezero)
if not insp.is_clause_element:
return insp.mapper
return None
def _only_mapper_zero(self, rationale=None):
if len(self._entities) > 1:
raise sa_exc.InvalidRequestError(
rationale or
"This operation requires a Query "
"against a single mapper."
)
return self._mapper_zero()
def _only_full_mapper_zero(self, methname):
if self._entities != [self._primary_entity]:
raise sa_exc.InvalidRequestError(
"%s() can only be used against "
"a single mapped class." % methname)
return self._primary_entity.entity_zero
def _only_entity_zero(self, rationale=None):
if len(self._entities) > 1:
raise sa_exc.InvalidRequestError(
rationale or
"This operation requires a Query "
"against a single mapper."
)
return self._entity_zero()
def __all_equivs(self):
equivs = {}
for ent in self._mapper_entities:
equivs.update(ent.mapper._equivalent_columns)
return equivs
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._criterion is not None or \
self._statement is not None or self._from_obj or \
self._limit is not None or self._offset is not None or \
self._group_by or (order_by and self._order_by) 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._statement = self._criterion = None
self._order_by = self._group_by = self._distinct = False
def _no_clauseelement_condition(self, meth):
if not self._enable_assertions:
return
if self._order_by:
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 is not None or self._offset is not None:
raise sa_exc.InvalidRequestError(
"Query.%s() being called on a Query which already has LIMIT "
"or OFFSET applied. To modify the row-limited results of a "
" Query, call from_self() first. "
"Otherwise, call %s() before limit() or offset() "
"are applied."
% (meth, meth)
)
def _get_options(self, populate_existing=None,
version_check=None,
only_load_props=None,
refresh_state=None):
if populate_existing:
self._populate_existing = populate_existing
if version_check:
self._version_check = version_check
if refresh_state:
self._refresh_state = refresh_state
if only_load_props:
self._only_load_props = set(only_load_props)
return self
def _clone(self):
cls = self.__class__
q = cls.__new__(cls)
q.__dict__ = self.__dict__.copy()
return q
@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.
"""
stmt = self._compile_context(labels=self._with_labels).\
statement
if self._params:
stmt = stmt.params(self._params)
# TODO: there's no tests covering effects of
# the annotation not being there
return stmt._annotate({'no_replacement_traverse': True})
def subquery(self, name=None, with_labels=False, reduce_columns=False):
"""return the full SELECT statement represented by
this :class:`.Query`, embedded within an :class:`.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:`.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` first to apply table-qualified labels
to all columns.
:param reduce_columns: if True, :meth:`.Select.reduce_columns` will
be called on the resulting :func:`.select` construct,
to remove same-named columns where one also refers to the other
via foreign key or WHERE clause equivalence.
.. versionchanged:: 0.8 the ``with_labels`` and ``reduce_columns``
keyword arguments were added.
"""
q = self.enable_eagerloads(False)
if with_labels:
q = q.with_labels()
q = q.statement
if reduce_columns:
q = q.reduce_columns()
return q.alias(name=name)
def cte(self, name=None, recursive=False):
"""Return the full SELECT statement represented by this
:class:`.Query` represented as a common table expression (CTE).
.. versionadded:: 0.7.6
Parameters and usage are the same as those of the
:meth:`.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:`.SelectBase.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`, converted
to a scalar subquery with a label of the given name.
Analogous to :meth:`sqlalchemy.sql.expression.SelectBase.label`.
.. versionadded:: 0.6.5
"""
return self.enable_eagerloads(False).statement.label(name)
def as_scalar(self):
"""Return the full SELECT statement represented by this
:class:`.Query`, converted to a scalar subquery.
Analogous to :meth:`sqlalchemy.sql.expression.SelectBase.as_scalar`.
.. versionadded:: 0.6.5
"""
return self.enable_eagerloads(False).statement.as_scalar()
@property
def selectable(self):
"""Return the :class:`.Select` object emitted by this :class:`.Query`.
Used for :func:`.inspect` compatibility, this is equivalent to::
query.enable_eagerloads(False).with_labels().statement
"""
return self.__clause_element__()
def __clause_element__(self):
return self.enable_eagerloads(False).with_labels().statement
@_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.yield_per`.
"""
self._enable_eagerloads = value
def _no_yield_per(self, message):
raise sa_exc.InvalidRequestError(
"The yield_per Query option is currently not "
"compatible with %s eager loading. Please "
"specify lazyload('*') or query.enable_eagerloads(False) in "
"order to "
"proceed with query.yield_per()." % message)
@_generative()
def with_labels(self):
"""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.with_labels` method *only* applies
the output of :attr:`.Query.statement`, and *not* to any of
the result-row invoking systems of :class:`.Query` itself, e.g.
:meth:`.Query.first`, :meth:`.Query.all`, etc. To execute
a query using :meth:`.Query.with_labels`, invoke the
:attr:`.Query.statement` using :meth:`.Session.execute`::
result = session.execute(query.with_labels().statement)
"""
self._with_labels = True
@_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 self._criterion
@_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._current_path = path
@_generative(_no_clauseelement_condition)
def with_polymorphic(self,
cls_or_mappers,
selectable=None,
polymorphic_on=None):
"""Load columns for inheriting classes.
:meth:`.Query.with_polymorphic` applies transformations
to the "main" mapped class represented by this :class:`.Query`.
The "main" mapped class here means the :class:`.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.
See the documentation section :ref:`with_polymorphic` for
details on how this method is used.
.. versionchanged:: 0.8
A new and more flexible function
:func:`.orm.with_polymorphic` supersedes
:meth:`.Query.with_polymorphic`, as it can apply the equivalent
functionality to any set of columns or classes in the
:class:`.Query`, not just the "zero mapper". See that
function for a description of arguments.
"""
if not self._primary_entity:
raise sa_exc.InvalidRequestError(
"No primary mapper set up for this Query.")
entity = self._entities[0]._clone()
self._entities = [entity] + self._entities[1:]
entity.set_with_polymorphic(self,
cls_or_mappers,
selectable=selectable,
polymorphic_on=polymorphic_on)
@_generative()
def yield_per(self, count):
"""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).
The :meth:`.Query.yield_per` method **is not compatible with most
eager loading schemes, including subqueryload and joinedload with
collections**. For this reason, it may be helpful to disable
eager loads, either unconditionally with
:meth:`.Query.enable_eagerloads`::
q = sess.query(Object).yield_per(100).enable_eagerloads(False)
Or more selectively using :func:`.lazyload`; such as with
an asterisk to specify the default loader scheme::
q = sess.query(Object).yield_per(100).\\
options(lazyload('*'), joinedload(Object.some_related))
.. warning::
Use this method with caution; if the same instance is
present in more than one batch of rows, end-user changes
to attributes will be overwritten.
In particular, it's usually impossible to use this setting
with eagerly loaded collections (i.e. any lazy='joined' or
'subquery') since those collections will be cleared for a
new load when encountered in a subsequent result batch.
In the case of 'subquery' loading, the full result for all
rows is fetched which generally defeats the purpose of
:meth:`~sqlalchemy.orm.query.Query.yield_per`.
Also note that while
:meth:`~sqlalchemy.orm.query.Query.yield_per` will set the
``stream_results`` execution option to True, currently
this is only understood by
:mod:`~sqlalchemy.dialects.postgresql.psycopg2` dialect
which will stream results using server side cursors
instead of pre-buffer all rows for this query. Other
DBAPIs **pre-buffer all rows** before making them
available. The memory use of raw database rows is much less
than that of an ORM-mapped object, but should still be taken into
consideration when benchmarking.
.. seealso::
:meth:`.Query.enable_eagerloads`
"""
self._yield_per = count
self._execution_options = self._execution_options.union(
{"stream_results": True,
"max_row_buffer": count})
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))
:meth:`~.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.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.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` must be constructed in this way,
i.e. against a single mapped entity,
with no additional filtering criterion. Loading
options via :meth:`~.Query.options` may be applied
however, and will be used if the object is not
yet locally present.
A lazy-loading, many-to-one attribute configured
by :func:`.relationship`, using a simple
foreign-key-to-primary-key criterion, will also use an
operation equivalent to :meth:`~.Query.get` in order to retrieve
the target value from the local identity map
before querying the database. See :doc:`/orm/loading_relationships`
for further details on relationship loading.
:param ident: A scalar or tuple value representing
the primary key. For a composite primary key,
the order of identifiers corresponds in most cases
to that of the mapped :class:`.Table` object's
primary key columns. For a :func:`.mapper` that
was given the ``primary key`` argument during
construction, the order of identifiers corresponds
to the elements present in this collection.
:return: The object instance, or ``None``.
"""
return self._get_impl(ident, loading.load_on_ident)
def _get_impl(self, ident, fallback_fn):
# convert composite types to individual args
if hasattr(ident, '__composite_values__'):
ident = ident.__composite_values__()
ident = util.to_list(ident)
mapper = self._only_full_mapper_zero("get")
if len(ident) != len(mapper.primary_key):
raise sa_exc.InvalidRequestError(
"Incorrect number of values in identifier to formulate "
"primary key for query.get(); primary key columns are %s" %
','.join("'%s'" % c for c in mapper.primary_key))
key = mapper.identity_key_from_primary_key(ident)
if not self._populate_existing and \
not mapper.always_refresh and \
self._for_update_arg is None:
instance = loading.get_from_identity(
self.session, key, attributes.PASSIVE_OFF)
if instance is not None:
self._get_existing_condition()
# reject calls for id in identity map but class
# mismatch.
if not issubclass(instance.__class__, mapper.class_):
return None
return instance
return fallback_fn(self, key)
@_generative()
def correlate(self, *args):
"""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:`.Select.correlate` after coercion to expression constructs.
The correlation arguments take effect in such cases
as when :meth:`.Query.from_self` is used, or when
a subquery as returned by :meth:`.Query.subquery` is
embedded in another :func:`~.expression.select` construct.
"""
self._correlate = self._correlate.union(
_interpret_as_from(s)
if s is not None else None
for s in args)
@_generative()
def autoflush(self, setting):
"""Return a Query with a specific 'autoflush' setting.
Note that a Session with autoflush=False will
not autoflush, even if this flag is set to True at the
Query level. Therefore this flag is usually used only
to disable autoflush for a specific Query.
"""
self._autoflush = setting
@_generative()
def populate_existing(self):
"""Return a :class:`.Query` that will expire and refresh all instances
as they are loaded, or reused from the current :class:`.Session`.
:meth:`.populate_existing` does not improve behavior when
the ORM is used normally - the :class:`.Session` object's usual
behavior of maintaining a transaction and expiring all attributes
after rollback or commit handles object state automatically.
This method is not intended for general use.
"""
self._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._invoke_all_eagers`.
"""
self._invoke_all_eagers = value
def with_parent(self, instance, property=None):
"""Add filtering criterion that relates the given instance
to a child object or collection, using its attribute state
as well as an established :func:`.relationship()`
configuration.
The method uses the :func:`.with_parent` function to generate
the clause, the result of which is passed to :meth:`.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` object's target mapper.
"""
if property is None:
mapper_zero = inspect(self._mapper_zero()).mapper
mapper = object_mapper(instance)
for prop in mapper.iterate_properties:
if isinstance(prop, properties.RelationshipProperty) and \
prop.mapper is mapper_zero:
property = prop
break
else:
raise sa_exc.InvalidRequestError(
"Could not locate a property which relates instances "
"of class '%s' to instances of class '%s'" %
(
self._mapper_zero().class_.__name__,
instance.__class__.__name__)
)
return self.filter(with_parent(instance, property))
@_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:
entity = aliased(entity, alias)
self._entities = list(self._entities)
m = _MapperEntity(self, entity)
self._set_entity_selectables([m])
@_generative()
def with_session(self, session):
"""Return a :class:`.Query` that will use the given :class:`.Session`.
"""
self.session = session
def from_self(self, *entities):
"""return a Query that selects from this Query's
SELECT statement.
:meth:`.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.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.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.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 wil 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.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.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.add_entity` above **before** we call
:meth:`.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.
"""
fromclause = self.with_labels().enable_eagerloads(False).\
statement.correlate(None)
q = self._from_selectable(fromclause)
q._enable_single_crit = False
q._select_from_entity = self._mapper_zero()
if entities:
q._set_entities(entities)
return q
@_generative()
def _set_enable_single_crit(self, val):
self._enable_single_crit = val
@_generative()
def _from_selectable(self, fromclause):
for attr in (
'_statement', '_criterion',
'_order_by', '_group_by',
'_limit', '_offset',
'_joinpath', '_joinpoint',
'_distinct', '_having',
'_prefixes', '_suffixes'
):
self.__dict__.pop(attr, None)
self._set_select_from([fromclause], True)
# this enables clause adaptation for non-ORM
# expressions.
self._orm_only_from_obj_alias = False
old_entities = self._entities
self._entities = []
for e in old_entities:
e.adapt_to_selectable(self, self._from_obj[0])
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()
q._set_entities(columns, entity_wrapper=_ColumnEntity)
if not q._yield_per:
q._yield_per = 10
return iter(q)
_values = values
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):
"""Return a new :class:`.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)
.. versionadded:: 0.6.5
"""
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._entities = list(self._entities)
l = len(self._entities)
for c in column:
_ColumnEntity(self, c)
# _ColumnEntity may add many entities if the
# given arg is a FROM clause
self._set_entity_selectables(self._entities[l:])
@util.pending_deprecation("0.7",
":meth:`.add_column` is superseded "
"by :meth:`.add_columns`",
False)
def add_column(self, column):
"""Add a column expression to the list of result columns to be
returned.
Pending deprecation: :meth:`.add_column` will be superseded by
:meth:`.add_columns`.
"""
return self.add_columns(column)
def options(self, *args):
"""Return a new Query object, applying the given list of
mapper options.
Most supplied options regard changing how column- and
relationship-mapped attributes are loaded. See the sections
:ref:`deferred` and :doc:`/orm/loading_relationships` for reference
documentation.
"""
return self._options(False, *args)
def _conditional_options(self, *args):
return self._options(True, *args)
@_generative()
def _options(self, conditional, *args):
# most MapperOptions write to the '_attributes' dictionary,
# so copy that as well
self._attributes = self._attributes.copy()
opts = tuple(util.flatten_iterator(args))
self._with_options = self._with_options + opts
if conditional:
for opt in opts:
opt.process_query_conditionally(self)
else:
for opt in opts:
opt.process_query(self)
def with_transformation(self, fn):
"""Return a new :class:`.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`
objects. See the example at :ref:`hybrid_transformers`.
.. versionadded:: 0.7.4
"""
return fn(self)
@_generative()
def with_hint(self, selectable, text, dialect_name='*'):
"""Add an indexing or other executional context
hint for the given entity or selectable to
this :class:`.Query`.
Functionality is passed straight through to
:meth:`~sqlalchemy.sql.expression.Select.with_hint`,
with the addition that ``selectable`` can be a
:class:`.Table`, :class:`.Alias`, or ORM entity / mapped class
/etc.
.. seealso::
:meth:`.Query.with_statement_hint`
"""
if selectable is not None:
selectable = inspect(selectable).selectable
self._with_hints += ((selectable, text, dialect_name),)
def with_statement_hint(self, text, dialect_name='*'):
"""add a statement hint to this :class:`.Select`.
This method is similar to :meth:`.Select.with_hint` except that
it does not require an individual table, and instead applies to the
statement as a whole.
This feature calls down into :meth:`.Select.with_statement_hint`.
.. versionadded:: 1.0.0
.. seealso::
:meth:`.Query.with_hint`
"""
return self.with_hint(None, text, dialect_name)
@_generative()
def execution_options(self, **kwargs):
""" Set non-SQL options which take effect during execution.
The options are the same as those accepted by
:meth:`.Connection.execution_options`.
Note that the ``stream_results`` execution option is enabled
automatically if the :meth:`~sqlalchemy.orm.query.Query.yield_per()`
method is used.
"""
self._execution_options = self._execution_options.union(kwargs)
@_generative()
def with_lockmode(self, mode):
"""Return a new :class:`.Query` object with the specified "locking mode",
which essentially refers to the ``FOR UPDATE`` clause.
.. deprecated:: 0.9.0 superseded by :meth:`.Query.with_for_update`.
:param mode: a string representing the desired locking mode.
Valid values are:
* ``None`` - translates to no lockmode
* ``'update'`` - translates to ``FOR UPDATE``
(standard SQL, supported by most dialects)
* ``'update_nowait'`` - translates to ``FOR UPDATE NOWAIT``
(supported by Oracle, PostgreSQL 8.1 upwards)
* ``'read'`` - translates to ``LOCK IN SHARE MODE`` (for MySQL),
and ``FOR SHARE`` (for PostgreSQL)
.. seealso::
:meth:`.Query.with_for_update` - improved API for
specifying the ``FOR UPDATE`` clause.
"""
self._for_update_arg = LockmodeArg.parse_legacy_query(mode)
@_generative()
def with_for_update(self, read=False, nowait=False, of=None):
"""return a new :class:`.Query` with the specified options for the
``FOR UPDATE`` clause.
The behavior of this method is identical to that of
:meth:`.SelectBase.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).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
.. versionadded:: 0.9.0 :meth:`.Query.with_for_update` supersedes
the :meth:`.Query.with_lockmode` method.
.. seealso::
:meth:`.GenerativeSelect.with_for_update` - Core level method with
full argument and behavioral description.
"""
self._for_update_arg = LockmodeArg(read=read, nowait=nowait, of=of)
@_generative()
def params(self, *args, **kwargs):
"""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.copy()
self._params.update(kwargs)
@_generative(_no_statement_condition, _no_limit_offset)
def filter(self, *criterion):
"""apply the given filtering criterion to a copy
of this :class:`.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:`.text` construct.
.. seealso::
:meth:`.Query.filter_by` - filter on keyword expressions.
"""
for criterion in list(criterion):
criterion = expression._expression_literal_as_text(criterion)
criterion = self._adapt_clause(criterion, True, True)
if self._criterion is not None:
self._criterion = self._criterion & criterion
else:
self._criterion = criterion
def filter_by(self, **kwargs):
"""apply the given filtering criterion to a copy
of this :class:`.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.join`.
.. seealso::
:meth:`.Query.filter` - filter on SQL expressions.
"""
clauses = [_entity_descriptor(self._joinpoint_zero(), key) == value
for key, value in kwargs.items()]
return self.filter(sql.and_(*clauses))
@_generative(_no_statement_condition, _no_limit_offset)
def order_by(self, *criterion):
"""apply one or more ORDER BY criterion to the query and return
the newly resulting ``Query``
All existing ORDER BY settings can be suppressed by
passing ``None`` - this will suppress any ORDER BY configured
on mappers as well.
Alternatively, an existing ORDER BY setting on the Query
object can be entirely cancelled by passing ``False``
as the value - use this before calling methods where
an ORDER BY is invalid.
"""
if len(criterion) == 1:
if criterion[0] is False:
if '_order_by' in self.__dict__:
del self._order_by
return
if criterion[0] is None:
self._order_by = None
return
criterion = self._adapt_col_list(criterion)
if self._order_by is False or self._order_by is None:
self._order_by = criterion
else:
self._order_by = self._order_by + criterion
@_generative(_no_statement_condition, _no_limit_offset)
def group_by(self, *criterion):
"""apply one or more GROUP BY criterion to the query and return
the newly resulting :class:`.Query`"""
criterion = list(chain(*[_orm_columns(c) for c in criterion]))
criterion = self._adapt_col_list(criterion)
if self._group_by is False:
self._group_by = criterion
else:
self._group_by = self._group_by + criterion
@_generative(_no_statement_condition, _no_limit_offset)
def having(self, criterion):
"""apply a HAVING criterion to the query and return the
newly resulting :class:`.Query`.
:meth:`~.Query.having` is used in conjunction with
:meth:`~.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)
"""
criterion = expression._expression_literal_as_text(criterion)
if criterion is not None and \
not isinstance(criterion, sql.ClauseElement):
raise sa_exc.ArgumentError(
"having() argument must be of type "
"sqlalchemy.sql.ClauseElement or string")
criterion = self._adapt_clause(criterion, True, True)
if self._having is not None:
self._having = self._having & criterion
else:
self._having = criterion
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` object will not render ORDER BY within
its SELECT statement.
"""
return self._from_selectable(
expression.union(*([self] + list(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._from_selectable(
expression.union_all(*([self] + list(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._from_selectable(
expression.intersect(*([self] + list(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._from_selectable(
expression.intersect_all(*([self] + list(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._from_selectable(
expression.except_(*([self] + list(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._from_selectable(
expression.except_all(*([self] + list(q)))
)
def join(self, *props, **kwargs):
"""Create a SQL JOIN against this :class:`.Query` object's criterion
and apply generatively, returning the newly resulting :class:`.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.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.join` along ``User.addresses``
will result in SQL equivalent to::
SELECT user.* FROM user JOIN address ON user.id = address.user_id
In the above example we refer to ``User.addresses`` as passed to
:meth:`~.Query.join` as the *on clause*, that is, it indicates
how the "ON" portion of the JOIN should be constructed. For a
single-entity query such as the one above (i.e. we start by selecting
only from ``User`` and nothing else), the relationship can also be
specified by its string name::
q = session.query(User).join("addresses")
:meth:`~.Query.join` can also accommodate multiple
"on clause" arguments to produce a chain of joins, such as below
where a join across four related entities is constructed::
q = session.query(User).join("orders", "items", "keywords")
The above would be shorthand for three separate calls to
:meth:`~.Query.join`, each using an explicit attribute to indicate
the source entity::
q = session.query(User).\\
join(User.orders).\\
join(Order.items).\\
join(Item.keywords)
**Joins to a Target Entity or Selectable**
A second form of :meth:`~.Query.join` allows any mapped entity
or core selectable construct as a target. In this usage,
:meth:`~.Query.join` will attempt
to create a JOIN along the natural foreign key relationship between
two entities::
q = session.query(User).join(Address)
The above calling form of :meth:`~.Query.join` will raise an error if
either there are no foreign keys between the two entities, or if
there are multiple foreign key linkages between them. In the
above calling form, :meth:`~.Query.join` is called upon to
create the "on clause" automatically for us. The target can
be any mapped entity or selectable, such as a :class:`.Table`::
q = session.query(User).join(addresses_table)
**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. Suppose for
example we wanted to join to ``Address`` twice, using
an alias the second time. We use :func:`~sqlalchemy.orm.aliased`
to create a distinct alias of ``Address``, and join
to it using the ``target, onclause`` form, so that the
alias can be specified explicitly as the target along with
the relationship to instruct how the ON clause should proceed::
a_alias = aliased(Address)
q = session.query(User).\\
join(User.addresses).\\
join(a_alias, User.addresses).\\
filter(Address.email_address=='ed@foo.com').\\
filter(a_alias.email_address=='ed@bar.com')
Where above, the generated SQL would be similar to::
SELECT user.* FROM user
JOIN address ON user.id = address.user_id
JOIN address AS address_1 ON user.id=address_1.user_id
WHERE address.email_address = :email_address_1
AND address_1.email_address = :email_address_2
The two-argument calling form of :meth:`~.Query.join`
also allows us to construct arbitrary joins with SQL-oriented
"on clause" expressions, not relying upon configured relationships
at all. Any SQL expression can be passed as the ON clause
when using the two-argument form, which should refer to the target
entity in some way as well as an applicable source entity::
q = session.query(User).join(Address, User.id==Address.user_id)
.. versionchanged:: 0.7
In SQLAlchemy 0.6 and earlier, the two argument form of
:meth:`~.Query.join` requires the usage of a tuple:
``query(User).join((Address, User.id==Address.user_id))``\ .
This calling form is accepted in 0.7 and further, though
is not necessary unless multiple join conditions are passed to
a single :meth:`~.Query.join` call, which itself is also not
generally necessary as it is now equivalent to multiple
calls (this wasn't always the case).
**Advanced Join Targeting and Adaption**
There is a lot of flexibility in what the "target" can be when using
:meth:`~.Query.join`. As noted previously, it also accepts
:class:`.Table` constructs and other selectables such as
:func:`.alias` and :func:`.select` constructs, with either the one
or two-argument forms::
addresses_q = select([Address.user_id]).\\
where(Address.email_address.endswith("@bar.com")).\\
alias()
q = session.query(User).\\
join(addresses_q, addresses_q.c.user_id==User.id)
:meth:`~.Query.join` also features the ability to *adapt* a
:meth:`~sqlalchemy.orm.relationship` -driven ON clause to the target
selectable. Below we construct a JOIN from ``User`` to a subquery
against ``Address``, allowing the relationship denoted by
``User.addresses`` to *adapt* itself to the altered target::
address_subq = session.query(Address).\\
filter(Address.email_address == 'ed@foo.com').\\
subquery()
q = session.query(User).join(address_subq, User.addresses)
Producing SQL similar to::
SELECT user.* FROM user
JOIN (
SELECT address.id AS id,
address.user_id AS user_id,
address.email_address AS email_address
FROM address
WHERE address.email_address = :email_address_1
) AS anon_1 ON user.id = anon_1.user_id
The above form allows one to fall back onto an explicit ON
clause at any time::
q = session.query(User).\\
join(address_subq, User.id==address_subq.c.user_id)
**Controlling what to Join From**
While :meth:`~.Query.join` exclusively deals with the "right"
side of the JOIN, we can also control the "left" side, in those
cases where it's needed, using :meth:`~.Query.select_from`.
Below we construct a query against ``Address`` but can still
make usage of ``User.addresses`` as our ON clause by instructing
the :class:`.Query` to select first from the ``User``
entity::
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
**Constructing Aliases Anonymously**
:meth:`~.Query.join` can construct anonymous aliases
using the ``aliased=True`` flag. This feature is useful
when a query is being joined algorithmically, such as
when querying self-referentially to an arbitrary depth::
q = session.query(Node).\\
join("children", "children", aliased=True)
When ``aliased=True`` is used, the actual "alias" construct
is not explicitly available. To work with it, methods such as
:meth:`.Query.filter` will adapt the incoming entity to
the last join point::
q = session.query(Node).\\
join("children", "children", aliased=True).\\
filter(Node.name == 'grandchild 1')
When using automatic aliasing, the ``from_joinpoint=True``
argument can allow a multi-node join to be broken into
multiple calls to :meth:`~.Query.join`, so that
each path along the way can be further filtered::
q = session.query(Node).\\
join("children", aliased=True).\\
filter(Node.name='child 1').\\
join("children", aliased=True, from_joinpoint=True).\\
filter(Node.name == 'grandchild 1')
The filtering aliases above can then be reset back to the
original ``Node`` entity using :meth:`~.Query.reset_joinpoint`::
q = session.query(Node).\\
join("children", "children", aliased=True).\\
filter(Node.name == 'grandchild 1').\\
reset_joinpoint().\\
filter(Node.name == 'parent 1)
For an example of ``aliased=True``, see the distribution
example :ref:`examples_xmlpersistence` which illustrates
an XPath-like query system using algorithmic joins.
:param \*props: A collection of one or more join conditions,
each consisting of a relationship-bound attribute or string
relationship name representing an "on clause", or a single
target entity, or a tuple in the form of ``(target, onclause)``.
A special two-argument calling form of the form ``target, onclause``
is also accepted.
:param aliased=False: If True, indicate that the JOIN target should be
anonymously aliased. Subsequent calls to :meth:`~.Query.filter`
and similar will adapt the incoming criterion to the target
alias, until :meth:`~.Query.reset_joinpoint` is called.
:param isouter=False: If True, the join used will be a left outer join,
just as if the :meth:`.Query.outerjoin` method were called. This
flag is here to maintain consistency with the same flag as accepted
by :meth:`.FromClause.join` and other Core constructs.
.. versionadded:: 1.0.0
: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.
.. seealso::
:ref:`ormtutorial_joins` in the ORM tutorial.
:ref:`inheritance_toplevel` for details on how
:meth:`~.Query.join` is used for inheritance relationships.
:func:`.orm.join` - a standalone ORM-level join function,
used internally by :meth:`.Query.join`, which in previous
SQLAlchemy versions was the primary ORM-level joining interface.
"""
aliased, from_joinpoint, isouter = kwargs.pop('aliased', False),\
kwargs.pop('from_joinpoint', False),\
kwargs.pop('isouter', False)
if kwargs:
raise TypeError("unknown arguments: %s" %
', '.join(sorted(kwargs)))
return self._join(props,
outerjoin=isouter, create_aliases=aliased,
from_joinpoint=from_joinpoint)
def outerjoin(self, *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.
"""
aliased, from_joinpoint = kwargs.pop('aliased', False), \
kwargs.pop('from_joinpoint', False)
if kwargs:
raise TypeError("unknown arguments: %s" %
', '.join(sorted(kwargs)))
return self._join(props,
outerjoin=True, create_aliases=aliased,
from_joinpoint=from_joinpoint)
def _update_joinpoint(self, jp):
self._joinpoint = jp
# copy backwards to the root of the _joinpath
# dict, so that no existing dict in the path is mutated
while 'prev' in jp:
f, prev = jp['prev']
prev = prev.copy()
prev[f] = jp
jp['prev'] = (f, prev)
jp = prev
self._joinpath = jp
@_generative(_no_statement_condition, _no_limit_offset)
def _join(self, keys, outerjoin, create_aliases, from_joinpoint):
"""consumes arguments from join() or outerjoin(), places them into a
consistent format with which to form the actual JOIN constructs.
"""
if not from_joinpoint:
self._reset_joinpoint()
if len(keys) == 2 and \
isinstance(keys[0], (expression.FromClause,
type, AliasedClass)) and \
isinstance(keys[1], (str, expression.ClauseElement,
interfaces.PropComparator)):
# detect 2-arg form of join and
# convert to a tuple.
keys = (keys,)
keylist = util.to_list(keys)
for idx, arg1 in enumerate(keylist):
if isinstance(arg1, tuple):
# "tuple" form of join, multiple
# tuples are accepted as well. The simpler
# "2-arg" form is preferred. May deprecate
# the "tuple" usage.
arg1, arg2 = arg1
else:
arg2 = None
# determine onclause/right_entity. there
# is a little bit of legacy behavior still at work here
# which means they might be in either order. may possibly
# lock this down to (right_entity, onclause) in 0.6.
if isinstance(
arg1, (interfaces.PropComparator, util.string_types)):
right_entity, onclause = arg2, arg1
else:
right_entity, onclause = arg1, arg2
left_entity = prop = None
if isinstance(onclause, interfaces.PropComparator):
of_type = getattr(onclause, '_of_type', None)
else:
of_type = None
if isinstance(onclause, util.string_types):
left_entity = self._joinpoint_zero()
descriptor = _entity_descriptor(left_entity, onclause)
onclause = descriptor
# check for q.join(Class.propname, from_joinpoint=True)
# and Class is that of the current joinpoint
elif from_joinpoint and \
isinstance(onclause, interfaces.PropComparator):
left_entity = onclause._parententity
info = inspect(self._joinpoint_zero())
left_mapper, left_selectable, left_is_aliased = \
getattr(info, 'mapper', None), \
info.selectable, \
getattr(info, 'is_aliased_class', None)
if left_mapper is left_entity:
left_entity = self._joinpoint_zero()
descriptor = _entity_descriptor(left_entity,
onclause.key)
onclause = descriptor
if isinstance(onclause, interfaces.PropComparator):
if right_entity is None:
if of_type:
right_entity = of_type
else:
right_entity = onclause.property.mapper
left_entity = onclause._parententity
prop = onclause.property
if not isinstance(onclause, attributes.QueryableAttribute):
onclause = prop
if not create_aliases:
# check for this path already present.
# don't render in that case.
edge = (left_entity, right_entity, prop.key)
if edge in self._joinpoint:
# The child's prev reference might be stale --
# it could point to a parent older than the
# current joinpoint. If this is the case,
# then we need to update it and then fix the
# tree's spine with _update_joinpoint. Copy
# and then mutate the child, which might be
# shared by a different query object.
jp = self._joinpoint[edge].copy()
jp['prev'] = (edge, self._joinpoint)
self._update_joinpoint(jp)
if idx == len(keylist) - 1:
util.warn(
"Pathed join target %s has already "
"been joined to; skipping" % prop)
continue
elif onclause is not None and right_entity is None:
# TODO: no coverage here
raise NotImplementedError("query.join(a==b) not supported.")
self._join_left_to_right(
left_entity,
right_entity, onclause,
outerjoin, create_aliases, prop)
def _join_left_to_right(self, left, right,
onclause, outerjoin, create_aliases, prop):
"""append a JOIN to the query's from clause."""
self._polymorphic_adapters = self._polymorphic_adapters.copy()
if left is None:
if self._from_obj:
left = self._from_obj[0]
elif self._entities:
left = self._entities[0].entity_zero_or_selectable
if left is None:
raise sa_exc.InvalidRequestError(
"Don't know how to join from %s; please use "
"select_from() to establish the left "
"entity/selectable of this join" % self._entities[0])
if left is right and \
not create_aliases:
raise sa_exc.InvalidRequestError(
"Can't construct a join from %s to %s, they "
"are the same entity" %
(left, right))
l_info = inspect(left)
r_info = inspect(right)
overlap = False
if not create_aliases:
right_mapper = getattr(r_info, "mapper", None)
# if the target is a joined inheritance mapping,
# be more liberal about auto-aliasing.
if right_mapper and (
right_mapper.with_polymorphic or
isinstance(right_mapper.mapped_table, expression.Join)
):
for from_obj in self._from_obj or [l_info.selectable]:
if sql_util.selectables_overlap(
l_info.selectable, from_obj) and \
sql_util.selectables_overlap(
from_obj, r_info.selectable):
overlap = True
break
if (overlap or not create_aliases) and \
l_info.selectable is r_info.selectable:
raise sa_exc.InvalidRequestError(
"Can't join table/selectable '%s' to itself" %
l_info.selectable)
right, onclause = self._prepare_right_side(
r_info, right, onclause,
create_aliases,
prop, overlap)
# if joining on a MapperProperty path,
# track the path to prevent redundant joins
if not create_aliases and prop:
self._update_joinpoint({
'_joinpoint_entity': right,
'prev': ((left, right, prop.key), self._joinpoint)
})
else:
self._joinpoint = {'_joinpoint_entity': right}
self._join_to_left(l_info, left, right, onclause, outerjoin)
def _prepare_right_side(self, r_info, right, onclause, create_aliases,
prop, overlap):
info = r_info
right_mapper, right_selectable, right_is_aliased = \
getattr(info, 'mapper', None), \
info.selectable, \
getattr(info, 'is_aliased_class', False)
if right_mapper:
self._join_entities += (info, )
if right_mapper and prop and \
not right_mapper.common_parent(prop.mapper):
raise sa_exc.InvalidRequestError(
"Join target %s does not correspond to "
"the right side of join condition %s" % (right, onclause)
)
if not right_mapper and prop:
right_mapper = prop.mapper
need_adapter = False
if right_mapper and right is right_selectable:
if not right_selectable.is_derived_from(
right_mapper.mapped_table):
raise sa_exc.InvalidRequestError(
"Selectable '%s' is not derived from '%s'" %
(right_selectable.description,
right_mapper.mapped_table.description))
if isinstance(right_selectable, expression.SelectBase):
# TODO: this isn't even covered now!
right_selectable = right_selectable.alias()
need_adapter = True
right = aliased(right_mapper, right_selectable)
aliased_entity = right_mapper and \
not right_is_aliased and \
(
right_mapper.with_polymorphic and isinstance(
right_mapper._with_polymorphic_selectable,
expression.Alias)
or
overlap # test for overlap:
# orm/inheritance/relationships.py
# SelfReferentialM2MTest
)
if not need_adapter and (create_aliases or aliased_entity):
right = aliased(right, flat=True)
need_adapter = True
# if an alias() of the right side was generated here,
# apply an adapter to all subsequent filter() calls
# until reset_joinpoint() is called.
if need_adapter:
self._filter_aliases = ORMAdapter(
right,
equivalents=right_mapper and
right_mapper._equivalent_columns or {},
chain_to=self._filter_aliases)
# if the onclause is a ClauseElement, adapt it with any
# adapters that are in place right now
if isinstance(onclause, expression.ClauseElement):
onclause = self._adapt_clause(onclause, True, True)
# if an alias() on the right side was generated,
# which is intended to wrap a the right side in a subquery,
# ensure that columns retrieved from this target in the result
# set are also adapted.
if aliased_entity and not create_aliases:
self._mapper_loads_polymorphically_with(
right_mapper,
ORMAdapter(
right,
equivalents=right_mapper._equivalent_columns
)
)
return right, onclause
def _join_to_left(self, l_info, left, right, onclause, outerjoin):
info = l_info
left_mapper = getattr(info, 'mapper', None)
left_selectable = info.selectable
if self._from_obj:
replace_clause_index, clause = sql_util.find_join_source(
self._from_obj,
left_selectable)
if clause is not None:
try:
clause = orm_join(clause,
right,
onclause, isouter=outerjoin)
except sa_exc.ArgumentError as ae:
raise sa_exc.InvalidRequestError(
"Could not find a FROM clause to join from. "
"Tried joining to %s, but got: %s" % (right, ae))
self._from_obj = \
self._from_obj[:replace_clause_index] + \
(clause, ) + \
self._from_obj[replace_clause_index + 1:]
return
if left_mapper:
for ent in self._entities:
if ent.corresponds_to(left):
clause = ent.selectable
break
else:
clause = left
else:
clause = left_selectable
assert clause is not None
try:
clause = orm_join(clause, right, onclause, isouter=outerjoin)
except sa_exc.ArgumentError as ae:
raise sa_exc.InvalidRequestError(
"Could not find a FROM clause to join from. "
"Tried joining to %s, but got: %s" % (right, ae))
self._from_obj = self._from_obj + (clause,)
def _reset_joinpoint(self):
self._joinpoint = self._joinpath
self._filter_aliases = None
@_generative(_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._reset_joinpoint()
@_generative(_no_clauseelement_condition)
def select_from(self, *from_obj):
"""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)
@_generative(_no_clauseelement_condition)
def select_entity_from(self, from_obj):
"""Set the FROM clause of this :class:`.Query` to a
core selectable, applying it as a replacement FROM clause
for corresponding mapped entities.
This method is similar to the :meth:`.Query.select_from`
method, in that it sets the FROM clause of the query. However,
where :meth:`.Query.select_from` only affects what is placed
in the FROM, this method also applies the given selectable
to replace the FROM which the selected entities would normally
select from.
The given ``from_obj`` must be an instance of a :class:`.FromClause`,
e.g. a :func:`.select` or :class:`.Alias` construct.
An example would be a :class:`.Query` that selects ``User`` entities,
but uses :meth:`.Query.select_entity_from` to have the entities
selected from a :func:`.select` construct instead of the
base ``user`` table::
select_stmt = select([User]).where(User.id == 7)
q = session.query(User).\\
select_entity_from(select_stmt).\\
filter(User.name == 'ed')
The query generated will select ``User`` entities directly
from the given :func:`.select` construct, and will be::
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
Notice above that even the WHERE criterion was "adapted" such that
the ``anon_1`` subquery effectively replaces all references to the
``user`` table, except for the one that it refers to internally.
Compare this to :meth:`.Query.select_from`, which as of
version 0.9, does not affect existing entities. The
statement below::
q = session.query(User).\\
select_from(select_stmt).\\
filter(User.name == 'ed')
Produces SQL where both the ``user`` table as well as the
``select_stmt`` construct are present as separate elements
in the FROM clause. No "adaptation" of the ``user`` table
is applied::
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
:meth:`.Query.select_entity_from` maintains an older
behavior of :meth:`.Query.select_from`. In modern usage,
similar results can also be achieved using :func:`.aliased`::
select_stmt = select([User]).where(User.id == 7)
user_from_select = aliased(User, select_stmt.alias())
q = session.query(user_from_select)
:param from_obj: a :class:`.FromClause` object that will replace
the FROM clause of this :class:`.Query`.
.. seealso::
:meth:`.Query.select_from`
.. versionadded:: 0.8
:meth:`.Query.select_entity_from` was added to specify
the specific behavior of entity replacement, however
the :meth:`.Query.select_from` maintains this behavior
as well until 0.9.
"""
self._set_select_from([from_obj], True)
def __getitem__(self, item):
if isinstance(item, slice):
start, stop, step = util.decode_slice(item)
if isinstance(stop, int) and \
isinstance(start, int) and \
stop - start <= 0:
return []
# perhaps we should execute a count() here so that we
# can still use LIMIT/OFFSET ?
elif (isinstance(start, int) and start < 0) \
or (isinstance(stop, int) and stop < 0):
return list(self)[item]
res = self.slice(start, stop)
if step is not None:
return list(res)[None:None:item.step]
else:
return list(res)
else:
if item == -1:
return list(self)[-1]
else:
return list(self[item:item + 1])[0]
@_generative(_no_statement_condition)
def slice(self, start, stop):
"""Computes the "slice" of the :class:`.Query` represented by
the given indices and returns the resulting :class:`.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.limit`
:meth:`.Query.offset`
"""
if start is not None and stop is not None:
self._offset = (self._offset or 0) + start
self._limit = stop - start
elif start is None and stop is not None:
self._limit = stop
elif start is not None and stop is None:
self._offset = (self._offset or 0) + start
if self._offset == 0:
self._offset = None
@_generative(_no_statement_condition)
def limit(self, limit):
"""Apply a ``LIMIT`` to the query and return the newly resulting
``Query``.
"""
self._limit = limit
@_generative(_no_statement_condition)
def offset(self, offset):
"""Apply an ``OFFSET`` to the query and return the newly resulting
``Query``.
"""
self._offset = offset
@_generative(_no_statement_condition)
def distinct(self, *criterion):
"""Apply a ``DISTINCT`` to the query and return the newly resulting
``Query``.
.. note::
The :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`, however, so would not affect results.
The columns are passed through when using the
:attr:`.Query.statement` accessor, however.
:param \*expr: optional column expressions. When present,
the Postgresql dialect will render a ``DISTINCT ON (<expressions>>)``
construct.
"""
if not criterion:
self._distinct = True
else:
criterion = self._adapt_col_list(criterion)
if isinstance(self._distinct, list):
self._distinct += criterion
else:
self._distinct = criterion
@_generative()
def prefix_with(self, *prefixes):
"""Apply the prefixes to the query and return the newly resulting
``Query``.
:param \*prefixes: optional prefixes, typically strings,
not using any commas. In particular is useful for MySQL keywords.
e.g.::
query = sess.query(User.name).\\
prefix_with('HIGH_PRIORITY').\\
prefix_with('SQL_SMALL_RESULT', 'ALL')
Would render::
SELECT HIGH_PRIORITY SQL_SMALL_RESULT ALL users.name AS users_name
FROM users
.. versionadded:: 0.7.7
.. seealso::
:meth:`.HasPrefixes.prefix_with`
"""
if self._prefixes:
self._prefixes += prefixes
else:
self._prefixes = prefixes
@_generative()
def suffix_with(self, *suffixes):
"""Apply the suffix to the query and return the newly resulting
``Query``.
:param \*suffixes: optional suffixes, typically strings,
not using any commas.
.. versionadded:: 1.0.0
.. seealso::
:meth:`.Query.prefix_with`
:meth:`.HasSuffixes.suffix_with`
"""
if self._suffixes:
self._suffixes += suffixes
else:
self._suffixes = suffixes
def all(self):
"""Return the results represented by this ``Query`` as a list.
This results in an execution of the underlying query.
"""
return list(self)
@_generative(_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`.
.. seealso::
:ref:`orm_tutorial_literal_sql` - usage examples in the
ORM tutorial
"""
statement = expression._expression_literal_as_text(statement)
if not isinstance(statement,
(expression.TextClause,
expression.SelectBase)):
raise sa_exc.ArgumentError(
"from_statement accepts text(), select(), "
"and union() objects only.")
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.first` results in an execution of the underlying query.
"""
if self._statement is not None:
ret = list(self)[0:1]
else:
ret = list(self[0:1])
if len(ret) > 0:
return ret[0]
else:
return None
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.one_or_none` results in an execution of the underlying
query.
.. versionadded:: 1.0.9
Added :meth:`.Query.one_or_none`
.. seealso::
:meth:`.Query.first`
:meth:`.Query.one`
"""
ret = list(self)
l = len(ret)
if l == 1:
return ret[0]
elif l == 0:
return None
else:
raise orm_exc.MultipleResultsFound(
"Multiple rows were found for 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.first`
:meth:`.Query.one_or_none`
"""
ret = list(self)
l = len(ret)
if l == 1:
return ret[0]
elif l == 0:
raise orm_exc.NoResultFound("No row was found for one()")
else:
raise orm_exc.MultipleResultsFound(
"Multiple rows were found for 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.
"""
try:
ret = self.one()
if not isinstance(ret, tuple):
return ret
return ret[0]
except orm_exc.NoResultFound:
return None
def __iter__(self):
context = self._compile_context()
context.statement.use_labels = True
if self._autoflush and not self._populate_existing:
self.session._autoflush()
return self._execute_and_instances(context)
def _connection_from_session(self, **kw):
conn = self.session.connection(
**kw)
if self._execution_options:
conn = conn.execution_options(**self._execution_options)
return conn
def _execute_and_instances(self, querycontext):
conn = self._connection_from_session(
mapper=self._bind_mapper(),
clause=querycontext.statement,
close_with_result=True)
result = conn.execute(querycontext.statement, self._params)
return loading.instances(querycontext.query, result, querycontext)
@property
def column_descriptions(self):
"""Return metadata about the columns which would be
returned by this :class:`.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 [
{
'name': ent._label_name,
'type': ent.type,
'aliased': getattr(insp_ent, 'is_aliased_class', False),
'expr': ent.expr,
'entity':
getattr(insp_ent, "entity", None)
if ent.entity_zero is not None
and not insp_ent.is_clause_element
else None
}
for ent, insp_ent in [
(
_ent,
(inspect(_ent.entity_zero)
if _ent.entity_zero is not None else None)
)
for _ent in self._entities
]
]
def instances(self, cursor, __context=None):
"""Given a ResultProxy cursor as returned by connection.execute(),
return an ORM result as an iterator.
e.g.::
result = engine.execute("select * from users")
for u in session.query(User).instances(result):
print u
"""
context = __context
if context is None:
context = QueryContext(self)
return loading.instances(self, cursor, context)
def merge_result(self, iterator, load=True):
"""Merge a result into this :class:`.Query` object's Session.
Given an iterator returned by a :class:`.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` - 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.merge_result` is used, see
the source code for the example :ref:`examples_caching`, where
:meth:`~.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)
@property
def _select_args(self):
return {
'limit': self._limit,
'offset': self._offset,
'distinct': self._distinct,
'prefixes': self._prefixes,
'suffixes': self._suffixes,
'group_by': self._group_by or None,
'having': self._having
}
@property
def _should_nest_selectable(self):
kwargs = self._select_args
return (kwargs.get('limit') is not None or
kwargs.get('offset') is not None or
kwargs.get('distinct', False))
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()
.. versionadded:: 0.8.1
"""
# .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.
return sql.exists(self.add_columns('1').with_labels().
statement.with_only_columns([1]))
def count(self):
"""Return a count of rows this 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
.. versionchanged:: 0.7
The above scheme is newly refined as of 0.7b3.
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).scalar()
def delete(self, synchronize_session='evaluate'):
"""Perform a bulk delete query.
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:: The :meth:`.Query.delete` method is a "bulk" operation,
which bypasses ORM unit-of-work automation in favor of greater
performance. **Please read all caveats and warnings below.**
:param synchronize_session: chooses the strategy for the removal of
matched objects from the session. Valid values are:
``False`` - don't synchronize the session. This option is the most
efficient and is reliable once the session is expired, which
typically occurs after a commit(), or explicitly using
expire_all(). Before the expiration, objects may still remain in
the session which were in fact deleted which can lead to confusing
results if they are accessed via get() or already loaded
collections.
``'fetch'`` - performs a select query before the delete to find
objects that are matched by the delete query and need to be
removed from the session. Matched objects are removed from the
session.
``'evaluate'`` - Evaluate the query's criteria in Python straight
on the objects in the session. If evaluation of the criteria isn't
implemented, an error is raised.
The expression evaluator currently doesn't account for differing
string collations between the database and Python.
:return: the count of rows matched as returned by the database's
"row count" feature.
.. warning:: **Additional Caveats for bulk query deletes**
* The method does **not** offer in-Python cascading of
relationships - it is assumed that ON DELETE CASCADE/SET
NULL/etc. is configured for any foreign key references
which require it, otherwise the database may emit an
integrity violation if foreign key references are being
enforced.
After the DELETE, dependent objects in the
:class:`.Session` which were impacted by an ON DELETE
may not contain the current state, or may have been
deleted. This issue is resolved once the
:class:`.Session` is expired, which normally occurs upon
:meth:`.Session.commit` or can be forced by using
:meth:`.Session.expire_all`. Accessing an expired
object whose row has been deleted will invoke a SELECT
to locate the row; when the row is not found, an
:class:`~sqlalchemy.orm.exc.ObjectDeletedError` is
raised.
* The ``'fetch'`` strategy results in an additional
SELECT statement emitted and will significantly reduce
performance.
* The ``'evaluate'`` strategy performs a scan of
all matching objects within the :class:`.Session`; if the
contents of the :class:`.Session` are expired, such as
via a proceeding :meth:`.Session.commit` call, **this will
result in SELECT queries emitted for every matching object**.
* The :meth:`.MapperEvents.before_delete` and
:meth:`.MapperEvents.after_delete`
events **are not invoked** from this method. Instead, the
:meth:`.SessionEvents.after_bulk_delete` method is provided to
act upon a mass DELETE of entity rows.
.. seealso::
:meth:`.Query.update`
:ref:`inserts_and_updates` - Core SQL tutorial
"""
# TODO: cascades need handling.
delete_op = persistence.BulkDelete.factory(
self, synchronize_session)
delete_op.exec_()
return delete_op.rowcount
def update(self, values, synchronize_session='evaluate', update_args=None):
"""Perform a bulk update query.
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:: The :meth:`.Query.update` method is a "bulk" operation,
which bypasses ORM unit-of-work automation in favor of greater
performance. **Please read all caveats and warnings below.**
: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.
.. versionchanged:: 1.0.0 - string names in the values dictionary
are now resolved against the mapped entity; previously, these
strings were passed as literal column names with no mapper-level
translation.
:param synchronize_session: chooses the strategy to update the
attributes on objects in the session. Valid values are:
``False`` - don't synchronize the session. This option is the most
efficient and is reliable once the session is expired, which
typically occurs after a commit(), or explicitly using
expire_all(). Before the expiration, updated objects may still
remain in the session with stale values on their attributes, which
can lead to confusing results.
``'fetch'`` - performs a select query before the update to find
objects that are matched by the update query. The updated
attributes are expired on matched objects.
``'evaluate'`` - Evaluate the Query's criteria in Python straight
on the objects in the session. If evaluation of the criteria isn't
implemented, an exception is raised.
The expression evaluator currently doesn't account for differing
string collations between the database and Python.
:param update_args: Optional dictionary, if present will be passed
to the underlying :func:`.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`.
.. versionadded:: 1.0.0
:return: the count of rows matched as returned by the database's
"row count" feature.
.. warning:: **Additional Caveats for bulk query updates**
* The method does **not** offer in-Python cascading of
relationships - it is assumed that ON UPDATE CASCADE is
configured for any foreign key references which require
it, otherwise the database may emit an integrity
violation if foreign key references are being enforced.
After the UPDATE, dependent objects in the
:class:`.Session` which were impacted by an ON UPDATE
CASCADE may not contain the current state; this issue is
resolved once the :class:`.Session` is expired, which
normally occurs upon :meth:`.Session.commit` or can be
forced by using :meth:`.Session.expire_all`.
* The ``'fetch'`` strategy results in an additional
SELECT statement emitted and will significantly reduce
performance.
* The ``'evaluate'`` strategy performs a scan of
all matching objects within the :class:`.Session`; if the
contents of the :class:`.Session` are expired, such as
via a proceeding :meth:`.Session.commit` call, **this will
result in SELECT queries emitted for every matching object**.
* The method supports multiple table updates, as detailed
in :ref:`multi_table_updates`, and this behavior does
extend to support updates of joined-inheritance and
other multiple table mappings. However, the **join
condition of an inheritance mapper is not
automatically rendered**. Care must be taken in any
multiple-table update to explicitly include the joining
condition between those tables, even in mappings where
this is normally automatic. E.g. if a class ``Engineer``
subclasses ``Employee``, an UPDATE of the ``Engineer``
local table using criteria against the ``Employee``
local table might look like::
session.query(Engineer).\\
filter(Engineer.id == Employee.id).\\
filter(Employee.name == 'dilbert').\\
update({"engineer_type": "programmer"})
* The :meth:`.MapperEvents.before_update` and
:meth:`.MapperEvents.after_update`
events **are not invoked from this method**. Instead, the
:meth:`.SessionEvents.after_bulk_update` method is provided to
act upon a mass UPDATE of entity rows.
.. seealso::
:meth:`.Query.delete`
:ref:`inserts_and_updates` - Core SQL tutorial
"""
update_args = update_args or {}
update_op = persistence.BulkUpdate.factory(
self, synchronize_session, values, update_args)
update_op.exec_()
return update_op.rowcount
def _compile_context(self, labels=True):
if self.dispatch.before_compile:
for fn in self.dispatch.before_compile:
new_query = fn(self)
if new_query is not None:
self = new_query
context = QueryContext(self)
if context.statement is not None:
return context
context.labels = labels
context._for_update_arg = self._for_update_arg
for entity in self._entities:
entity.setup_context(self, context)
for rec in context.create_eager_joins:
strategy = rec[0]
strategy(*rec[1:])
if context.from_clause:
# "load from explicit FROMs" mode,
# i.e. when select_from() or join() is used
context.froms = list(context.from_clause)
# else "load from discrete FROMs" mode,
# i.e. when each _MappedEntity has its own FROM
if self._enable_single_crit:
self._adjust_for_single_inheritance(context)
if not context.primary_columns:
if self._only_load_props:
raise sa_exc.InvalidRequestError(
"No column-based properties specified for "
"refresh operation. Use session.expire() "
"to reload collections and related items.")
else:
raise sa_exc.InvalidRequestError(
"Query contains no columns with which to "
"SELECT from.")
if context.multi_row_eager_loaders and self._should_nest_selectable:
context.statement = self._compound_eager_statement(context)
else:
context.statement = self._simple_statement(context)
return context
def _compound_eager_statement(self, context):
# for eager joins present and LIMIT/OFFSET/DISTINCT,
# wrap the query inside a select,
# then append eager joins onto that
if context.order_by:
order_by_col_expr = list(
chain(*[
sql_util.unwrap_order_by(o)
for o in context.order_by
])
)
else:
context.order_by = None
order_by_col_expr = []
inner = sql.select(
context.primary_columns + order_by_col_expr,
context.whereclause,
from_obj=context.froms,
use_labels=context.labels,
# TODO: this order_by is only needed if
# LIMIT/OFFSET is present in self._select_args,
# else the application on the outside is enough
order_by=context.order_by,
**self._select_args
)
for hint in self._with_hints:
inner = inner.with_hint(*hint)
if self._correlate:
inner = inner.correlate(*self._correlate)
inner = inner.alias()
equivs = self.__all_equivs()
context.adapter = sql_util.ColumnAdapter(inner, equivs)
statement = sql.select(
[inner] + context.secondary_columns,
use_labels=context.labels)
statement._for_update_arg = context._for_update_arg
from_clause = inner
for eager_join in context.eager_joins.values():
# EagerLoader places a 'stop_on' attribute on the join,
# giving us a marker as to where the "splice point" of
# the join should be
from_clause = sql_util.splice_joins(
from_clause,
eager_join, eager_join.stop_on)
statement.append_from(from_clause)
if context.order_by:
statement.append_order_by(
*context.adapter.copy_and_process(
context.order_by
)
)
statement.append_order_by(*context.eager_order_by)
return statement
def _simple_statement(self, context):
if not context.order_by:
context.order_by = None
if self._distinct and context.order_by:
order_by_col_expr = list(
chain(*[
sql_util.unwrap_order_by(o)
for o in context.order_by
])
)
context.primary_columns += order_by_col_expr
context.froms += tuple(context.eager_joins.values())
statement = sql.select(
context.primary_columns +
context.secondary_columns,
context.whereclause,
from_obj=context.froms,
use_labels=context.labels,
order_by=context.order_by,
**self._select_args
)
statement._for_update_arg = context._for_update_arg
for hint in self._with_hints:
statement = statement.with_hint(*hint)
if self._correlate:
statement = statement.correlate(*self._correlate)
if context.eager_order_by:
statement.append_order_by(*context.eager_order_by)
return statement
def _adjust_for_single_inheritance(self, context):
"""Apply single-table-inheritance filtering.
For all distinct single-table-inheritance mappers represented in
the columns clause of this query, add criterion to the WHERE
clause of the given QueryContext such that only the appropriate
subtypes are selected from the total results.
"""
for (ext_info, adapter) in set(self._mapper_adapter_map.values()):
if ext_info in self._join_entities:
continue
single_crit = ext_info.mapper._single_table_criterion
if single_crit is not None:
if adapter:
single_crit = adapter.traverse(single_crit)
single_crit = self._adapt_clause(single_crit, False, False)
context.whereclause = sql.and_(
sql.True_._ifnone(context.whereclause),
single_crit)
def __str__(self):
return str(self._compile_context().statement)
from ..sql.selectable import ForUpdateArg
class LockmodeArg(ForUpdateArg):
@classmethod
def parse_legacy_query(self, mode):
if mode in (None, False):
return None
if mode == "read":
read = True
nowait = False
elif mode == "update":
read = nowait = False
elif mode == "update_nowait":
nowait = True
read = False
else:
raise sa_exc.ArgumentError(
"Unknown with_lockmode argument: %r" % mode)
return LockmodeArg(read=read, nowait=nowait)
class _QueryEntity(object):
"""represent an entity column returned within a Query result."""
def __new__(cls, *args, **kwargs):
if cls is _QueryEntity:
entity = args[1]
if not isinstance(entity, util.string_types) and \
_is_mapped_class(entity):
cls = _MapperEntity
elif isinstance(entity, Bundle):
cls = _BundleEntity
else:
cls = _ColumnEntity
return object.__new__(cls)
def _clone(self):
q = self.__class__.__new__(self.__class__)
q.__dict__ = self.__dict__.copy()
return q
class _MapperEntity(_QueryEntity):
"""mapper/class/AliasedClass entity"""
def __init__(self, query, entity):
if not query._primary_entity:
query._primary_entity = self
query._entities.append(self)
self.entities = [entity]
self.expr = entity
supports_single_entity = True
def setup_entity(self, ext_info, aliased_adapter):
self.mapper = ext_info.mapper
self.aliased_adapter = aliased_adapter
self.selectable = ext_info.selectable
self.is_aliased_class = ext_info.is_aliased_class
self._with_polymorphic = ext_info.with_polymorphic_mappers
self._polymorphic_discriminator = \
ext_info.polymorphic_on
self.entity_zero = ext_info
if ext_info.is_aliased_class:
self._label_name = self.entity_zero.name
else:
self._label_name = self.mapper.class_.__name__
self.path = self.entity_zero._path_registry
def set_with_polymorphic(self, query, cls_or_mappers,
selectable, polymorphic_on):
"""Receive an update from a call to query.with_polymorphic().
Note the newer style of using a free standing with_polymporphic()
construct doesn't make use of this method.
"""
if self.is_aliased_class:
# TODO: invalidrequest ?
raise NotImplementedError(
"Can't use with_polymorphic() against "
"an Aliased object"
)
if cls_or_mappers is None:
query._reset_polymorphic_adapter(self.mapper)
return
mappers, from_obj = self.mapper._with_polymorphic_args(
cls_or_mappers, selectable)
self._with_polymorphic = mappers
self._polymorphic_discriminator = polymorphic_on
self.selectable = from_obj
query._mapper_loads_polymorphically_with(
self.mapper, sql_util.ColumnAdapter(
from_obj, self.mapper._equivalent_columns))
filter_fn = id
@property
def type(self):
return self.mapper.class_
@property
def entity_zero_or_selectable(self):
return self.entity_zero
def corresponds_to(self, entity):
if entity.is_aliased_class:
if self.is_aliased_class:
if entity._base_alias is self.entity_zero._base_alias:
return True
return False
elif self.is_aliased_class:
if self.entity_zero._use_mapper_path:
return entity in self._with_polymorphic
else:
return entity is self.entity_zero
return entity.common_parent(self.entity_zero)
def adapt_to_selectable(self, query, sel):
query._entities.append(self)
def _get_entity_clauses(self, query, context):
adapter = None
if not self.is_aliased_class:
if query._polymorphic_adapters:
adapter = query._polymorphic_adapters.get(self.mapper, None)
else:
adapter = self.aliased_adapter
if adapter:
if query._from_obj_alias:
ret = adapter.wrap(query._from_obj_alias)
else:
ret = adapter
else:
ret = query._from_obj_alias
return ret
def row_processor(self, query, context, result):
adapter = self._get_entity_clauses(query, context)
if context.adapter and adapter:
adapter = adapter.wrap(context.adapter)
elif not adapter:
adapter = context.adapter
# polymorphic mappers which have concrete tables in
# their hierarchy usually
# require row aliasing unconditionally.
if not adapter and self.mapper._requires_row_aliasing:
adapter = sql_util.ColumnAdapter(
self.selectable,
self.mapper._equivalent_columns)
if query._primary_entity is self:
only_load_props = query._only_load_props
refresh_state = context.refresh_state
else:
only_load_props = refresh_state = None
_instance = loading._instance_processor(
self.mapper,
context,
result,
self.path,
adapter,
only_load_props=only_load_props,
refresh_state=refresh_state,
polymorphic_discriminator=self._polymorphic_discriminator
)
return _instance, self._label_name
def setup_context(self, query, context):
adapter = self._get_entity_clauses(query, context)
# if self._adapted_selectable is None:
context.froms += (self.selectable,)
if context.order_by is False and self.mapper.order_by:
context.order_by = self.mapper.order_by
# apply adaptation to the mapper's order_by if needed.
if adapter:
context.order_by = adapter.adapt_list(
util.to_list(
context.order_by
)
)
loading._setup_entity_query(
context, self.mapper, self,
self.path, adapter, context.primary_columns,
with_polymorphic=self._with_polymorphic,
only_load_props=query._only_load_props,
polymorphic_discriminator=self._polymorphic_discriminator)
def __str__(self):
return str(self.mapper)
@inspection._self_inspects
class Bundle(InspectionAttr):
"""A grouping of SQL expressions that are returned by a :class:`.Query`
under one namespace.
The :class:`.Bundle` essentially allows nesting of the tuple-based
results returned by a column-oriented :class:`.Query` object. It also
is extensible via simple subclassing, where the primary capability
to override is that of how the set of expressions should be returned,
allowing post-processing as well as custom return types, without
involving ORM identity-mapped classes.
.. versionadded:: 0.9.0
.. seealso::
:ref:`bundles`
"""
single_entity = False
"""If True, queries for a single Bundle will be returned as a single
entity, rather than an element within a keyed tuple."""
is_clause_element = False
is_mapper = False
is_aliased_class = False
def __init__(self, name, *exprs, **kw):
"""Construct a new :class:`.Bundle`.
e.g.::
bn = Bundle("mybundle", MyClass.x, MyClass.y)
for row in session.query(bn).filter(
bn.c.x == 5).filter(bn.c.y == 4):
print(row.mybundle.x, row.mybundle.y)
:param name: name of the bundle.
:param \*exprs: columns or SQL expressions comprising the bundle.
:param single_entity=False: if True, rows for this :class:`.Bundle`
can be returned as a "single entity" outside of any enclosing tuple
in the same manner as a mapped entity.
"""
self.name = self._label = name
self.exprs = exprs
self.c = self.columns = ColumnCollection()
self.columns.update((getattr(col, "key", col._label), col)
for col in exprs)
self.single_entity = kw.pop('single_entity', self.single_entity)
columns = None
"""A namespace of SQL expressions referred to by this :class:`.Bundle`.
e.g.::
bn = Bundle("mybundle", MyClass.x, MyClass.y)
q = sess.query(bn).filter(bn.c.x == 5)
Nesting of bundles is also supported::
b1 = Bundle("b1",
Bundle('b2', MyClass.a, MyClass.b),
Bundle('b3', MyClass.x, MyClass.y)
)
q = sess.query(b1).filter(
b1.c.b2.c.a == 5).filter(b1.c.b3.c.y == 9)
.. seealso::
:attr:`.Bundle.c`
"""
c = None
"""An alias for :attr:`.Bundle.columns`."""
def _clone(self):
cloned = self.__class__.__new__(self.__class__)
cloned.__dict__.update(self.__dict__)
return cloned
def __clause_element__(self):
return expression.ClauseList(group=False, *self.c)
@property
def clauses(self):
return self.__clause_element__().clauses
def label(self, name):
"""Provide a copy of this :class:`.Bundle` passing a new label."""
cloned = self._clone()
cloned.name = name
return cloned
def create_row_processor(self, query, procs, labels):
"""Produce the "row processing" function for this :class:`.Bundle`.
May be overridden by subclasses.
.. seealso::
:ref:`bundles` - includes an example of subclassing.
"""
keyed_tuple = util.lightweight_named_tuple('result', labels)
def proc(row):
return keyed_tuple([proc(row) for proc in procs])
return proc
class _BundleEntity(_QueryEntity):
def __init__(self, query, bundle, setup_entities=True):
query._entities.append(self)
self.bundle = self.expr = bundle
self.type = type(bundle)
self._label_name = bundle.name
self._entities = []
if setup_entities:
for expr in bundle.exprs:
if isinstance(expr, Bundle):
_BundleEntity(self, expr)
else:
_ColumnEntity(self, expr, namespace=self)
self.entities = ()
self.filter_fn = lambda item: item
self.supports_single_entity = self.bundle.single_entity
@property
def entity_zero(self):
for ent in self._entities:
ezero = ent.entity_zero
if ezero is not None:
return ezero
else:
return None
def corresponds_to(self, entity):
# TODO: this seems to have no effect for
# _ColumnEntity either
return False
@property
def entity_zero_or_selectable(self):
for ent in self._entities:
ezero = ent.entity_zero_or_selectable
if ezero is not None:
return ezero
else:
return None
def adapt_to_selectable(self, query, sel):
c = _BundleEntity(query, self.bundle, setup_entities=False)
# c._label_name = self._label_name
# c.entity_zero = self.entity_zero
# c.entities = self.entities
for ent in self._entities:
ent.adapt_to_selectable(c, sel)
def setup_entity(self, ext_info, aliased_adapter):
for ent in self._entities:
ent.setup_entity(ext_info, aliased_adapter)
def setup_context(self, query, context):
for ent in self._entities:
ent.setup_context(query, context)
def row_processor(self, query, context, result):
procs, labels = zip(
*[ent.row_processor(query, context, result)
for ent in self._entities]
)
proc = self.bundle.create_row_processor(query, procs, labels)
return proc, self._label_name
class _ColumnEntity(_QueryEntity):
"""Column/expression based entity."""
def __init__(self, query, column, namespace=None):
self.expr = column
self.namespace = namespace
search_entities = True
check_column = False
if isinstance(column, util.string_types):
column = sql.literal_column(column)
self._label_name = column.name
search_entities = False
check_column = True
_entity = None
elif isinstance(column, (
attributes.QueryableAttribute,
interfaces.PropComparator
)):
_entity = getattr(column, '_parententity', None)
if _entity is not None:
search_entities = False
self._label_name = column.key
column = column._query_clause_element()
check_column = True
if isinstance(column, Bundle):
_BundleEntity(query, column)
return
if not isinstance(column, sql.ColumnElement):
if hasattr(column, '_select_iterable'):
# break out an object like Table into
# individual columns
for c in column._select_iterable:
if c is column:
break
_ColumnEntity(query, c, namespace=column)
else:
return
raise sa_exc.InvalidRequestError(
"SQL expression, column, or mapped entity "
"expected - got '%r'" % (column, )
)
elif not check_column:
self._label_name = getattr(column, 'key', None)
search_entities = True
self.type = type_ = column.type
if type_.hashable:
self.filter_fn = lambda item: item
else:
counter = util.counter()
self.filter_fn = lambda item: counter()
# If the Column is unnamed, give it a
# label() so that mutable column expressions
# can be located in the result even
# if the expression's identity has been changed
# due to adaption.
if not column._label and not getattr(column, 'is_literal', False):
column = column.label(self._label_name)
query._entities.append(self)
self.column = column
self.froms = set()
# look for ORM entities represented within the
# given expression. Try to count only entities
# for columns whose FROM object is in the actual list
# of FROMs for the overall expression - this helps
# subqueries which were built from ORM constructs from
# leaking out their entities into the main select construct
self.actual_froms = actual_froms = set(column._from_objects)
if not search_entities:
self.entity_zero = _entity
if _entity:
self.entities = [_entity]
else:
self.entities = []
self._from_entities = set(self.entities)
else:
all_elements = [
elem for elem in visitors.iterate(column, {})
if 'parententity' in elem._annotations
]
self.entities = util.unique_list([
elem._annotations['parententity']
for elem in all_elements
if 'parententity' in elem._annotations
])
self._from_entities = set([
elem._annotations['parententity']
for elem in all_elements
if 'parententity' in elem._annotations
and actual_froms.intersection(elem._from_objects)
])
if self.entities:
self.entity_zero = self.entities[0]
elif self.namespace is not None:
self.entity_zero = self.namespace
else:
self.entity_zero = None
supports_single_entity = False
@property
def entity_zero_or_selectable(self):
if self.entity_zero is not None:
return self.entity_zero
elif self.actual_froms:
return list(self.actual_froms)[0]
else:
return None
def adapt_to_selectable(self, query, sel):
c = _ColumnEntity(query, sel.corresponding_column(self.column))
c._label_name = self._label_name
c.entity_zero = self.entity_zero
c.entities = self.entities
def setup_entity(self, ext_info, aliased_adapter):
if 'selectable' not in self.__dict__:
self.selectable = ext_info.selectable
if self.actual_froms.intersection(ext_info.selectable._from_objects):
self.froms.add(ext_info.selectable)
def corresponds_to(self, entity):
# TODO: just returning False here,
# no tests fail
if self.entity_zero is None:
return False
elif _is_aliased_class(entity):
# TODO: polymorphic subclasses ?
return entity is self.entity_zero
else:
return not _is_aliased_class(self.entity_zero) and \
entity.common_parent(self.entity_zero)
def row_processor(self, query, context, result):
if ('fetch_column', self) in context.attributes:
column = context.attributes[('fetch_column', self)]
else:
column = query._adapt_clause(self.column, False, True)
if context.adapter:
column = context.adapter.columns[column]
getter = result._getter(column)
return getter, self._label_name
def setup_context(self, query, context):
column = query._adapt_clause(self.column, False, True)
context.froms += tuple(self.froms)
context.primary_columns.append(column)
context.attributes[('fetch_column', self)] = column
def __str__(self):
return str(self.column)
class QueryContext(object):
__slots__ = (
'multi_row_eager_loaders', 'adapter', 'froms', 'for_update',
'query', 'session', 'autoflush', 'populate_existing',
'invoke_all_eagers', 'version_check', 'refresh_state',
'primary_columns', 'secondary_columns', 'eager_order_by',
'eager_joins', 'create_eager_joins', 'propagate_options',
'attributes', 'statement', 'from_clause', 'whereclause',
'order_by', 'labels', '_for_update_arg', 'runid', 'partials'
)
def __init__(self, query):
if query._statement is not None:
if isinstance(query._statement, expression.SelectBase) and \
not query._statement._textual and \
not query._statement.use_labels:
self.statement = query._statement.apply_labels()
else:
self.statement = query._statement
else:
self.statement = None
self.from_clause = query._from_obj
self.whereclause = query._criterion
self.order_by = query._order_by
self.multi_row_eager_loaders = False
self.adapter = None
self.froms = ()
self.for_update = None
self.query = query
self.session = query.session
self.autoflush = query._autoflush
self.populate_existing = query._populate_existing
self.invoke_all_eagers = query._invoke_all_eagers
self.version_check = query._version_check
self.refresh_state = query._refresh_state
self.primary_columns = []
self.secondary_columns = []
self.eager_order_by = []
self.eager_joins = {}
self.create_eager_joins = []
self.propagate_options = set(o for o in query._with_options if
o.propagate_to_loaders)
self.attributes = query._attributes.copy()
class AliasOption(interfaces.MapperOption):
def __init__(self, alias):
"""Return a :class:`.MapperOption` that will indicate to the :class:`.Query`
that the main table has been aliased.
This is a seldom-used option to suit the
very rare case that :func:`.contains_eager`
is being used in conjunction with a user-defined SELECT
statement that aliases the parent table. E.g.::
# define an aliased UNION called 'ulist'
ulist = users.select(users.c.user_id==7).\\
union(users.select(users.c.user_id>7)).\\
alias('ulist')
# add on an eager load of "addresses"
statement = ulist.outerjoin(addresses).\\
select().apply_labels()
# create query, indicating "ulist" will be an
# alias for the main table, "addresses"
# property should be eager loaded
query = session.query(User).options(
contains_alias(ulist),
contains_eager(User.addresses))
# then get results via the statement
results = query.from_statement(statement).all()
:param alias: is the string name of an alias, or a
:class:`~.sql.expression.Alias` object representing
the alias.
"""
self.alias = alias
def process_query(self, query):
if isinstance(self.alias, util.string_types):
alias = query._mapper_zero().mapped_table.alias(self.alias)
else:
alias = self.alias
query._from_obj_alias = sql_util.ColumnAdapter(alias)
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