# orm/query.py
# Copyright (C) 2005-2021 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php

"""The Query class and support.

Defines the :class:`_query.Query` class, the central
construct used by the ORM to construct database queries.

The :class:`_query.Query` class should not be confused with the
:class:`_expression.Select` class, which defines database
SELECT operations at the SQL (non-ORM) level.  ``Query`` differs from
``Select`` in that it returns ORM-mapped objects and interacts with an
ORM session, whereas the ``Select`` construct interacts directly with the
database to return iterable result sets.

"""
import itertools
import operator
import types

from . import exc as orm_exc
from . import interfaces
from . import loading
from . import util as orm_util
from .base import _assertions
from .context import _column_descriptions
from .context import _legacy_determine_last_joined_entity
from .context import _legacy_filter_by_entity_zero
from .context import LABEL_STYLE_LEGACY_ORM
from .context import ORMCompileState
from .context import ORMFromStatementCompileState
from .context import QueryContext
from .interfaces import ORMColumnsClauseRole
from .util import aliased
from .util import AliasedClass
from .util import object_mapper
from .util import with_parent
from .util import with_polymorphic
from .. import exc as sa_exc
from .. import inspect
from .. import inspection
from .. import log
from .. import sql
from .. import util
from ..sql import coercions
from ..sql import expression
from ..sql import roles
from ..sql import Select
from ..sql import util as sql_util
from ..sql.annotation import SupportsCloneAnnotations
from ..sql.base import _entity_namespace_key
from ..sql.base import _generative
from ..sql.base import Executable
from ..sql.selectable import _SelectFromElements
from ..sql.selectable import ForUpdateArg
from ..sql.selectable import GroupedElement
from ..sql.selectable import HasHints
from ..sql.selectable import HasPrefixes
from ..sql.selectable import HasSuffixes
from ..sql.selectable import LABEL_STYLE_TABLENAME_PLUS_COL
from ..sql.selectable import SelectBase
from ..sql.selectable import SelectStatementGrouping
from ..sql.visitors import InternalTraversal
from ..util import collections_abc

__all__ = ["Query", "QueryContext", "aliased"]


@inspection._self_inspects
@log.class_logger
class Query(
    _SelectFromElements,
    SupportsCloneAnnotations,
    HasPrefixes,
    HasSuffixes,
    HasHints,
    Executable,
):

    """ORM-level SQL construction object.

    :class:`_query.Query`
    is the source of all SELECT statements generated by the
    ORM, both those formulated by end-user query operations as well as by
    high level internal operations such as related collection loading.  It
    features a generative interface whereby successive calls return a new
    :class:`_query.Query` object, a copy of the former with additional
    criteria and options associated with it.

    :class:`_query.Query` objects are normally initially generated using the
    :meth:`~.Session.query` method of :class:`.Session`, and in
    less common cases by instantiating the :class:`_query.Query` directly and
    associating with a :class:`.Session` using the
    :meth:`_query.Query.with_session`
    method.

    For a full walk through of :class:`_query.Query` usage, see the
    :ref:`ormtutorial_toplevel`.

    """

    # elements that are in Core and can be cached in the same way
    _where_criteria = ()
    _having_criteria = ()

    _order_by_clauses = ()
    _group_by_clauses = ()
    _limit_clause = None
    _offset_clause = None

    _distinct = False
    _distinct_on = ()

    _for_update_arg = None
    _correlate = ()
    _auto_correlate = True
    _from_obj = ()
    _setup_joins = ()
    _legacy_setup_joins = ()
    _label_style = LABEL_STYLE_LEGACY_ORM

    _compile_options = ORMCompileState.default_compile_options

    load_options = QueryContext.default_load_options

    _params = util.EMPTY_DICT

    # local Query builder state, not needed for
    # compilation or execution
    _aliased_generation = None
    _enable_assertions = True
    _last_joined_entity = None
    _statement = None

    # mirrors that of ClauseElement, used to propagate the "orm"
    # plugin as well as the "subject" of the plugin, e.g. the mapper
    # we are querying against.
    _propagate_attrs = util.immutabledict()

    def __init__(self, entities, session=None):
        """Construct a :class:`_query.Query` directly.

        E.g.::

            q = Query([User, Address], session=some_session)

        The above is equivalent to::

            q = some_session.query(User, Address)

        :param entities: a sequence of entities and/or SQL expressions.

        :param session: a :class:`.Session` with which the
         :class:`_query.Query`
         will be associated.   Optional; a :class:`_query.Query`
         can be associated
         with a :class:`.Session` generatively via the
         :meth:`_query.Query.with_session` method as well.

        .. seealso::

            :meth:`.Session.query`

            :meth:`_query.Query.with_session`

        """

        self.session = session
        self._set_entities(entities)

    def _set_propagate_attrs(self, values):
        self._propagate_attrs = util.immutabledict(values)
        return self

    def _set_entities(self, entities):
        self._raw_columns = [
            coercions.expect(
                roles.ColumnsClauseRole, ent, apply_propagate_attrs=self
            )
            for ent in util.to_list(entities)
        ]

    def _entity_from_pre_ent_zero(self):
        if not self._raw_columns:
            return None

        ent = self._raw_columns[0]

        if "parententity" in ent._annotations:
            return ent._annotations["parententity"]
        elif isinstance(ent, ORMColumnsClauseRole):
            return ent.entity
        elif "bundle" in ent._annotations:
            return ent._annotations["bundle"]
        else:
            return ent

    def _only_full_mapper_zero(self, methname):
        if (
            len(self._raw_columns) != 1
            or "parententity" not in self._raw_columns[0]._annotations
            or not self._raw_columns[0].is_selectable
        ):
            raise sa_exc.InvalidRequestError(
                "%s() can only be used against "
                "a single mapped class." % methname
            )

        return self._raw_columns[0]._annotations["parententity"]

    def _set_select_from(self, obj, set_base_alias):
        fa = [
            coercions.expect(
                roles.StrictFromClauseRole,
                elem,
                allow_select=True,
                apply_propagate_attrs=self,
            )
            for elem in obj
        ]

        self._compile_options += {"_set_base_alias": set_base_alias}
        self._from_obj = tuple(fa)

    @_generative
    def _set_lazyload_from(self, state):
        self.load_options += {"_lazy_loaded_from": state}

    def _get_condition(self):
        return self._no_criterion_condition(
            "get", order_by=False, distinct=False
        )

    def _get_existing_condition(self):
        self._no_criterion_assertion("get", order_by=False, distinct=False)

    def _no_criterion_assertion(self, meth, order_by=True, distinct=True):
        if not self._enable_assertions:
            return
        if (
            self._where_criteria
            or self._statement is not None
            or self._from_obj
            or self._legacy_setup_joins
            or self._limit_clause is not None
            or self._offset_clause is not None
            or self._group_by_clauses
            or (order_by and self._order_by_clauses)
            or (distinct and self._distinct)
        ):
            raise sa_exc.InvalidRequestError(
                "Query.%s() being called on a "
                "Query with existing criterion. " % meth
            )

    def _no_criterion_condition(self, meth, order_by=True, distinct=True):
        self._no_criterion_assertion(meth, order_by, distinct)

        self._from_obj = self._legacy_setup_joins = ()
        if self._statement is not None:
            self._compile_options += {"_statement": None}
        self._where_criteria = ()
        self._distinct = False

        self._order_by_clauses = self._group_by_clauses = ()

    def _no_clauseelement_condition(self, meth):
        if not self._enable_assertions:
            return
        if self._order_by_clauses:
            raise sa_exc.InvalidRequestError(
                "Query.%s() being called on a "
                "Query with existing criterion. " % meth
            )
        self._no_criterion_condition(meth)

    def _no_statement_condition(self, meth):
        if not self._enable_assertions:
            return
        if self._statement is not None:
            raise sa_exc.InvalidRequestError(
                (
                    "Query.%s() being called on a Query with an existing full "
                    "statement - can't apply criterion."
                )
                % meth
            )

    def _no_limit_offset(self, meth):
        if not self._enable_assertions:
            return
        if self._limit_clause is not None or self._offset_clause is not None:
            raise sa_exc.InvalidRequestError(
                "Query.%s() being called on a Query which already has LIMIT "
                "or OFFSET applied. To modify the row-limited results of a "
                " Query, call from_self() first.  "
                "Otherwise, call %s() before limit() or offset() "
                "are applied." % (meth, meth)
            )

    @property
    def _has_row_limiting_clause(self):
        return (
            self._limit_clause is not None or self._offset_clause is not None
        )

    def _get_options(
        self,
        populate_existing=None,
        version_check=None,
        only_load_props=None,
        refresh_state=None,
        identity_token=None,
    ):
        load_options = {}
        compile_options = {}

        if version_check:
            load_options["_version_check"] = version_check
        if populate_existing:
            load_options["_populate_existing"] = populate_existing
        if refresh_state:
            load_options["_refresh_state"] = refresh_state
            compile_options["_for_refresh_state"] = True
        if only_load_props:
            compile_options["_only_load_props"] = frozenset(only_load_props)
        if identity_token:
            load_options["_refresh_identity_token"] = identity_token

        if load_options:
            self.load_options += load_options
        if compile_options:
            self._compile_options += compile_options

        return self

    def _clone(self):
        return self._generate()

    @property
    def statement(self):
        """The full SELECT statement represented by this Query.

        The statement by default will not have disambiguating labels
        applied to the construct unless with_labels(True) is called
        first.

        """

        # .statement can return the direct future.Select() construct here, as
        # long as we are not using subsequent adaption features that
        # are made against raw entities, e.g. from_self(), with_polymorphic(),
        # select_entity_from().  If these features are being used, then
        # the Select() we return will not have the correct .selected_columns
        # collection and will not embed in subsequent queries correctly.
        # We could find a way to make this collection "correct", however
        # this would not be too different from doing the full compile as
        # we are doing in any case, the Select() would still not have the
        # proper state for other attributes like whereclause, order_by,
        # and these features are all deprecated in any case.
        #
        # for these reasons, Query is not a Select, it remains an ORM
        # object for which __clause_element__() must be called in order for
        # it to provide a real expression object.
        #
        # from there, it starts to look much like Query itself won't be
        # passed into the execute process and wont generate its own cache
        # key; this will all occur in terms of the ORM-enabled Select.
        if (
            not self._compile_options._set_base_alias
            and not self._compile_options._with_polymorphic_adapt_map
        ):
            # if we don't have legacy top level aliasing features in use
            # then convert to a future select() directly
            stmt = self._statement_20(for_statement=True)
        else:
            stmt = self._compile_state(for_statement=True).statement

        if self._params:
            stmt = stmt.params(self._params)

        return stmt

    def _final_statement(self, legacy_query_style=True):
        """Return the 'final' SELECT statement for this :class:`.Query`.

        This is the Core-only select() that will be rendered by a complete
        compilation of this query, and is what .statement used to return
        in 1.3.

        This method creates a complete compile state so is fairly expensive.

        """

        q = self._clone()

        return q._compile_state(
            use_legacy_query_style=legacy_query_style
        ).statement

    def _statement_20(self, for_statement=False, use_legacy_query_style=True):
        # TODO: this event needs to be deprecated, as it currently applies
        # only to ORM query and occurs at this spot that is now more
        # or less an artificial spot
        if self.dispatch.before_compile:
            for fn in self.dispatch.before_compile:
                new_query = fn(self)
                if new_query is not None and new_query is not self:
                    self = new_query
                    if not fn._bake_ok:
                        self._compile_options += {"_bake_ok": False}

        compile_options = self._compile_options
        compile_options += {
            "_for_statement": for_statement,
            "_use_legacy_query_style": use_legacy_query_style,
        }

        if self._statement is not None:
            stmt = FromStatement(self._raw_columns, self._statement)
            stmt.__dict__.update(
                _with_options=self._with_options,
                _with_context_options=self._with_context_options,
                _compile_options=compile_options,
                _execution_options=self._execution_options,
                _propagate_attrs=self._propagate_attrs,
            )
        else:
            # Query / select() internal attributes are 99% cross-compatible
            stmt = Select.__new__(Select)
            stmt.__dict__.update(self.__dict__)
            stmt.__dict__.update(
                _label_style=self._label_style,
                _compile_options=compile_options,
                _propagate_attrs=self._propagate_attrs,
            )
            stmt.__dict__.pop("session", None)

        # ensure the ORM context is used to compile the statement, even
        # if it has no ORM entities.  This is so ORM-only things like
        # _legacy_joins are picked up that wouldn't be picked up by the
        # Core statement context
        if "compile_state_plugin" not in stmt._propagate_attrs:
            stmt._propagate_attrs = stmt._propagate_attrs.union(
                {"compile_state_plugin": "orm", "plugin_subject": None}
            )

        return stmt

    def subquery(
        self,
        name=None,
        with_labels=False,
        reduce_columns=False,
    ):
        """Return the full SELECT statement represented by
        this :class:`_query.Query`, embedded within an
        :class:`_expression.Alias`.

        Eager JOIN generation within the query is disabled.

        :param name: string name to be assigned as the alias;
            this is passed through to :meth:`_expression.FromClause.alias`.
            If ``None``, a name will be deterministically generated
            at compile time.

        :param with_labels: if True, :meth:`.with_labels` will be called
         on the :class:`_query.Query` first to apply table-qualified labels
         to all columns.

        :param reduce_columns: if True,
         :meth:`_expression.Select.reduce_columns` will
         be called on the resulting :func:`_expression.select` construct,
         to remove same-named columns where one also refers to the other
         via foreign key or WHERE clause equivalence.

        """
        q = self.enable_eagerloads(False)
        if with_labels:
            q = q.set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)

        q = q.statement

        if reduce_columns:
            q = q.reduce_columns()
        return q.alias(name=name)

    def cte(self, name=None, recursive=False):
        r"""Return the full SELECT statement represented by this
        :class:`_query.Query` represented as a common table expression (CTE).

        Parameters and usage are the same as those of the
        :meth:`_expression.SelectBase.cte` method; see that method for
        further details.

        Here is the `PostgreSQL WITH
        RECURSIVE example
        <http://www.postgresql.org/docs/8.4/static/queries-with.html>`_.
        Note that, in this example, the ``included_parts`` cte and the
        ``incl_alias`` alias of it are Core selectables, which
        means the columns are accessed via the ``.c.`` attribute.  The
        ``parts_alias`` object is an :func:`_orm.aliased` instance of the
        ``Part`` entity, so column-mapped attributes are available
        directly::

            from sqlalchemy.orm import aliased

            class Part(Base):
                __tablename__ = 'part'
                part = Column(String, primary_key=True)
                sub_part = Column(String, primary_key=True)
                quantity = Column(Integer)

            included_parts = session.query(
                            Part.sub_part,
                            Part.part,
                            Part.quantity).\
                                filter(Part.part=="our part").\
                                cte(name="included_parts", recursive=True)

            incl_alias = aliased(included_parts, name="pr")
            parts_alias = aliased(Part, name="p")
            included_parts = included_parts.union_all(
                session.query(
                    parts_alias.sub_part,
                    parts_alias.part,
                    parts_alias.quantity).\
                        filter(parts_alias.part==incl_alias.c.sub_part)
                )

            q = session.query(
                    included_parts.c.sub_part,
                    func.sum(included_parts.c.quantity).
                        label('total_quantity')
                ).\
                group_by(included_parts.c.sub_part)

        .. seealso::

            :meth:`_expression.HasCTE.cte`

        """
        return self.enable_eagerloads(False).statement.cte(
            name=name, recursive=recursive
        )

    def label(self, name):
        """Return the full SELECT statement represented by this
        :class:`_query.Query`, converted
        to a scalar subquery with a label of the given name.

        Analogous to :meth:`sqlalchemy.sql.expression.SelectBase.label`.

        """

        return self.enable_eagerloads(False).statement.label(name)

    @util.deprecated(
        "1.4",
        "The :meth:`_query.Query.as_scalar` method is deprecated and will be "
        "removed in a future release.  Please refer to "
        ":meth:`_query.Query.scalar_subquery`.",
    )
    def as_scalar(self):
        """Return the full SELECT statement represented by this
        :class:`_query.Query`, converted to a scalar subquery.

        """
        return self.scalar_subquery()

    def scalar_subquery(self):
        """Return the full SELECT statement represented by this
        :class:`_query.Query`, converted to a scalar subquery.

        Analogous to
        :meth:`sqlalchemy.sql.expression.SelectBase.scalar_subquery`.

        .. versionchanged:: 1.4 The :meth:`_query.Query.scalar_subquery`
           method replaces the :meth:`_query.Query.as_scalar` method.

        """

        return self.enable_eagerloads(False).statement.scalar_subquery()

    def __clause_element__(self):
        return (
            self.enable_eagerloads(False)
            .set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)
            .statement
        )

    @_generative
    def only_return_tuples(self, value):
        """When set to True, the query results will always be a tuple.

        This is specifically for single element queries. The default is False.

        .. versionadded:: 1.2.5

        .. seealso::

            :meth:`_query.Query.is_single_entity`

        """
        self.load_options += dict(_only_return_tuples=value)

    @property
    def is_single_entity(self):
        """Indicates if this :class:`_query.Query`
        returns tuples or single entities.

        Returns True if this query returns a single entity for each instance
        in its result list, and False if this query returns a tuple of entities
        for each result.

        .. versionadded:: 1.3.11

        .. seealso::

            :meth:`_query.Query.only_return_tuples`

        """
        return (
            not self.load_options._only_return_tuples
            and len(self._raw_columns) == 1
            and "parententity" in self._raw_columns[0]._annotations
            and isinstance(
                self._raw_columns[0]._annotations["parententity"],
                ORMColumnsClauseRole,
            )
        )

    @_generative
    def enable_eagerloads(self, value):
        """Control whether or not eager joins and subqueries are
        rendered.

        When set to False, the returned Query will not render
        eager joins regardless of :func:`~sqlalchemy.orm.joinedload`,
        :func:`~sqlalchemy.orm.subqueryload` options
        or mapper-level ``lazy='joined'``/``lazy='subquery'``
        configurations.

        This is used primarily when nesting the Query's
        statement into a subquery or other
        selectable, or when using :meth:`_query.Query.yield_per`.

        """
        self._compile_options += {"_enable_eagerloads": value}

    @util.deprecated_20(
        ":meth:`_orm.Query.with_labels` and :meth:`_orm.Query.apply_labels`",
        alternative="Use set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL) "
        "instead.",
    )
    def with_labels(self):
        return self.set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)

    apply_labels = with_labels

    @property
    def get_label_style(self):
        """
        Retrieve the current label style.

        .. versionadded:: 1.4

        """
        return self._label_style

    def set_label_style(self, style):
        """Apply column labels to the return value of Query.statement.

        Indicates that this Query's `statement` accessor should return
        a SELECT statement that applies labels to all columns in the
        form <tablename>_<columnname>; this is commonly used to
        disambiguate columns from multiple tables which have the same
        name.

        When the `Query` actually issues SQL to load rows, it always
        uses column labeling.

        .. note:: The :meth:`_query.Query.set_label_style` method *only* applies
           the output of :attr:`_query.Query.statement`, and *not* to any of
           the result-row invoking systems of :class:`_query.Query` itself,
           e.g.
           :meth:`_query.Query.first`, :meth:`_query.Query.all`, etc.
           To execute
           a query using :meth:`_query.Query.set_label_style`, invoke the
           :attr:`_query.Query.statement` using :meth:`.Session.execute`::

                result = session.execute(
                    query
                    .set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)
                    .statement
                )

        .. versionadded:: 1.4

        """  # noqa
        if self._label_style is not style:
            self = self._generate()
            self._label_style = style
        return self

    @_generative
    def enable_assertions(self, value):
        """Control whether assertions are generated.

        When set to False, the returned Query will
        not assert its state before certain operations,
        including that LIMIT/OFFSET has not been applied
        when filter() is called, no criterion exists
        when get() is called, and no "from_statement()"
        exists when filter()/order_by()/group_by() etc.
        is called.  This more permissive mode is used by
        custom Query subclasses to specify criterion or
        other modifiers outside of the usual usage patterns.

        Care should be taken to ensure that the usage
        pattern is even possible.  A statement applied
        by from_statement() will override any criterion
        set by filter() or order_by(), for example.

        """
        self._enable_assertions = value

    @property
    def whereclause(self):
        """A readonly attribute which returns the current WHERE criterion for
        this Query.

        This returned value is a SQL expression construct, or ``None`` if no
        criterion has been established.

        """
        return sql.elements.BooleanClauseList._construct_for_whereclause(
            self._where_criteria
        )

    @_generative
    def _with_current_path(self, path):
        """indicate that this query applies to objects loaded
        within a certain path.

        Used by deferred loaders (see strategies.py) which transfer
        query options from an originating query to a newly generated
        query intended for the deferred load.

        """
        self._compile_options += {"_current_path": path}

    @_generative
    @_assertions(_no_clauseelement_condition)
    @util.deprecated_20(
        ":meth:`_orm.Query.with_polymorphic`",
        alternative="Use the orm.with_polymorphic() standalone function",
    )
    def with_polymorphic(
        self, cls_or_mappers, selectable=None, polymorphic_on=None
    ):
        """Load columns for inheriting classes.

        :meth:`_query.Query.with_polymorphic` applies transformations
        to the "main" mapped class represented by this :class:`_query.Query`.
        The "main" mapped class here means the :class:`_query.Query`
        object's first argument is a full class, i.e.
        ``session.query(SomeClass)``. These transformations allow additional
        tables to be present in the FROM clause so that columns for a
        joined-inheritance subclass are available in the query, both for the
        purposes of load-time efficiency as well as the ability to use
        these columns at query time.

        See the documentation section :ref:`with_polymorphic` for
        details on how this method is used.

        """

        entity = _legacy_filter_by_entity_zero(self)

        wp = with_polymorphic(
            entity,
            cls_or_mappers,
            selectable=selectable,
            polymorphic_on=polymorphic_on,
        )

        self._compile_options = self._compile_options.add_to_element(
            "_with_polymorphic_adapt_map", ((entity, inspect(wp)),)
        )

    @_generative
    def yield_per(self, count):
        r"""Yield only ``count`` rows at a time.

        The purpose of this method is when fetching very large result sets
        (> 10K rows), to batch results in sub-collections and yield them
        out partially, so that the Python interpreter doesn't need to declare
        very large areas of memory which is both time consuming and leads
        to excessive memory use.   The performance from fetching hundreds of
        thousands of rows can often double when a suitable yield-per setting
        (e.g. approximately 1000) is used, even with DBAPIs that buffer
        rows (which are most).

        As of SQLAlchemy 1.4, the :meth:`_orm.Query.yield_per` method is
        equivalent to using the ``yield_per`` execution option at the ORM
        level. See the section :ref:`orm_queryguide_yield_per` for further
        background on this option.

        """
        self.load_options += {"_yield_per": count}

    @util.deprecated_20(
        ":meth:`_orm.Query.get`",
        alternative="The method is now available as :meth:`_orm.Session.get`",
        becomes_legacy=True,
    )
    def get(self, ident):
        """Return an instance based on the given primary key identifier,
        or ``None`` if not found.

        E.g.::

            my_user = session.query(User).get(5)

            some_object = session.query(VersionedFoo).get((5, 10))

            some_object = session.query(VersionedFoo).get(
                {"id": 5, "version_id": 10})

        :meth:`_query.Query.get` is special in that it provides direct
        access to the identity map of the owning :class:`.Session`.
        If the given primary key identifier is present
        in the local identity map, the object is returned
        directly from this collection and no SQL is emitted,
        unless the object has been marked fully expired.
        If not present,
        a SELECT is performed in order to locate the object.

        :meth:`_query.Query.get` also will perform a check if
        the object is present in the identity map and
        marked as expired - a SELECT
        is emitted to refresh the object as well as to
        ensure that the row is still present.
        If not, :class:`~sqlalchemy.orm.exc.ObjectDeletedError` is raised.

        :meth:`_query.Query.get` is only used to return a single
        mapped instance, not multiple instances or
        individual column constructs, and strictly
        on a single primary key value.  The originating
        :class:`_query.Query` must be constructed in this way,
        i.e. against a single mapped entity,
        with no additional filtering criterion.  Loading
        options via :meth:`_query.Query.options` may be applied
        however, and will be used if the object is not
        yet locally present.

        :param ident: A scalar, tuple, or dictionary representing the
         primary key.  For a composite (e.g. multiple column) primary key,
         a tuple or dictionary should be passed.

         For a single-column primary key, the scalar calling form is typically
         the most expedient.  If the primary key of a row is the value "5",
         the call looks like::

            my_object = query.get(5)

         The tuple form contains primary key values typically in
         the order in which they correspond to the mapped
         :class:`_schema.Table`
         object's primary key columns, or if the
         :paramref:`_orm.Mapper.primary_key` configuration parameter were
         used, in
         the order used for that parameter. For example, if the primary key
         of a row is represented by the integer
         digits "5, 10" the call would look like::

             my_object = query.get((5, 10))

         The dictionary form should include as keys the mapped attribute names
         corresponding to each element of the primary key.  If the mapped class
         has the attributes ``id``, ``version_id`` as the attributes which
         store the object's primary key value, the call would look like::

            my_object = query.get({"id": 5, "version_id": 10})

         .. versionadded:: 1.3 the :meth:`_query.Query.get`
            method now optionally
            accepts a dictionary of attribute names to values in order to
            indicate a primary key identifier.


        :return: The object instance, or ``None``.

        """
        self._no_criterion_assertion("get", order_by=False, distinct=False)

        # we still implement _get_impl() so that baked query can override
        # it
        return self._get_impl(ident, loading.load_on_pk_identity)

    def _get_impl(self, primary_key_identity, db_load_fn, identity_token=None):
        mapper = self._only_full_mapper_zero("get")
        return self.session._get_impl(
            mapper,
            primary_key_identity,
            db_load_fn,
            populate_existing=self.load_options._populate_existing,
            with_for_update=self._for_update_arg,
            options=self._with_options,
            identity_token=identity_token,
            execution_options=self._execution_options,
        )

    @property
    def lazy_loaded_from(self):
        """An :class:`.InstanceState` that is using this :class:`_query.Query`
        for a lazy load operation.

        .. deprecated:: 1.4  This attribute should be viewed via the
           :attr:`.ORMExecuteState.lazy_loaded_from` attribute, within
           the context of the :meth:`.SessionEvents.do_orm_execute`
           event.

        .. seealso::

            :attr:`.ORMExecuteState.lazy_loaded_from`

        """
        return self.load_options._lazy_loaded_from

    @property
    def _current_path(self):
        return self._compile_options._current_path

    @_generative
    def correlate(self, *fromclauses):
        """Return a :class:`.Query` construct which will correlate the given
        FROM clauses to that of an enclosing :class:`.Query` or
        :func:`~.expression.select`.

        The method here accepts mapped classes, :func:`.aliased` constructs,
        and :func:`.mapper` constructs as arguments, which are resolved into
        expression constructs, in addition to appropriate expression
        constructs.

        The correlation arguments are ultimately passed to
        :meth:`_expression.Select.correlate`
        after coercion to expression constructs.

        The correlation arguments take effect in such cases
        as when :meth:`_query.Query.from_self` is used, or when
        a subquery as returned by :meth:`_query.Query.subquery` is
        embedded in another :func:`_expression.select` construct.

        """

        self._auto_correlate = False
        if fromclauses and fromclauses[0] in {None, False}:
            self._correlate = ()
        else:
            self._correlate = set(self._correlate).union(
                coercions.expect(roles.FromClauseRole, f) for f in fromclauses
            )

    @_generative
    def autoflush(self, setting):
        """Return a Query with a specific 'autoflush' setting.

        As of SQLAlchemy 1.4, the :meth:`_orm.Query.autoflush` method
        is equivalent to using the ``autoflush`` execution option at the
        ORM level. See the section :ref:`orm_queryguide_autoflush` for
        further background on this option.

        """
        self.load_options += {"_autoflush": setting}

    @_generative
    def populate_existing(self):
        """Return a :class:`_query.Query`
        that will expire and refresh all instances
        as they are loaded, or reused from the current :class:`.Session`.

        As of SQLAlchemy 1.4, the :meth:`_orm.Query.populate_existing` method
        is equivalent to using the ``populate_existing`` execution option at
        the ORM level. See the section :ref:`orm_queryguide_populate_existing`
        for further background on this option.

        """
        self.load_options += {"_populate_existing": True}

    @_generative
    def _with_invoke_all_eagers(self, value):
        """Set the 'invoke all eagers' flag which causes joined- and
        subquery loaders to traverse into already-loaded related objects
        and collections.

        Default is that of :attr:`_query.Query._invoke_all_eagers`.

        """
        self.load_options += {"_invoke_all_eagers": value}

    @util.deprecated_20(
        ":meth:`_orm.Query.with_parent`",
        alternative="Use the :func:`_orm.with_parent` standalone construct.",
        becomes_legacy=True,
    )
    @util.preload_module("sqlalchemy.orm.relationships")
    def with_parent(self, instance, property=None, from_entity=None):  # noqa
        """Add filtering criterion that relates the given instance
        to a child object or collection, using its attribute state
        as well as an established :func:`_orm.relationship()`
        configuration.

        The method uses the :func:`.with_parent` function to generate
        the clause, the result of which is passed to
        :meth:`_query.Query.filter`.

        Parameters are the same as :func:`.with_parent`, with the exception
        that the given property can be None, in which case a search is
        performed against this :class:`_query.Query` object's target mapper.

        :param instance:
          An instance which has some :func:`_orm.relationship`.

        :param property:
          String property name, or class-bound attribute, which indicates
          what relationship from the instance should be used to reconcile the
          parent/child relationship.

        :param from_entity:
          Entity in which to consider as the left side.  This defaults to the
          "zero" entity of the :class:`_query.Query` itself.

        """
        relationships = util.preloaded.orm_relationships

        if from_entity:
            entity_zero = inspect(from_entity)
        else:
            entity_zero = _legacy_filter_by_entity_zero(self)
        if property is None:
            # TODO: deprecate, property has to be supplied
            mapper = object_mapper(instance)

            for prop in mapper.iterate_properties:
                if (
                    isinstance(prop, relationships.RelationshipProperty)
                    and prop.mapper is entity_zero.mapper
                ):
                    property = prop  # noqa
                    break
            else:
                raise sa_exc.InvalidRequestError(
                    "Could not locate a property which relates instances "
                    "of class '%s' to instances of class '%s'"
                    % (
                        entity_zero.mapper.class_.__name__,
                        instance.__class__.__name__,
                    )
                )

        return self.filter(with_parent(instance, property, entity_zero.entity))

    @_generative
    def add_entity(self, entity, alias=None):
        """add a mapped entity to the list of result columns
        to be returned."""

        if alias is not None:
            # TODO: deprecate
            entity = aliased(entity, alias)

        self._raw_columns = list(self._raw_columns)

        self._raw_columns.append(
            coercions.expect(
                roles.ColumnsClauseRole, entity, apply_propagate_attrs=self
            )
        )

    @_generative
    def with_session(self, session):
        """Return a :class:`_query.Query` that will use the given
        :class:`.Session`.

        While the :class:`_query.Query`
        object is normally instantiated using the
        :meth:`.Session.query` method, it is legal to build the
        :class:`_query.Query`
        directly without necessarily using a :class:`.Session`.  Such a
        :class:`_query.Query` object, or any :class:`_query.Query`
        already associated
        with a different :class:`.Session`, can produce a new
        :class:`_query.Query`
        object associated with a target session using this method::

            from sqlalchemy.orm import Query

            query = Query([MyClass]).filter(MyClass.id == 5)

            result = query.with_session(my_session).one()

        """

        self.session = session

    @util.deprecated_20(
        ":meth:`_query.Query.from_self`",
        alternative="The new approach is to use the :func:`.orm.aliased` "
        "construct in conjunction with a subquery.  See the section "
        ":ref:`Selecting from the query itself as a subquery "
        "<migration_20_query_from_self>` in the 2.0 migration notes for an "
        "example.",
    )
    def from_self(self, *entities):
        r"""return a Query that selects from this Query's
        SELECT statement.

        :meth:`_query.Query.from_self` essentially turns the SELECT statement
        into a SELECT of itself.  Given a query such as::

            q = session.query(User).filter(User.name.like('e%'))

        Given the :meth:`_query.Query.from_self` version::

            q = session.query(User).filter(User.name.like('e%')).from_self()

        This query renders as:

        .. sourcecode:: sql

            SELECT anon_1.user_id AS anon_1_user_id,
                   anon_1.user_name AS anon_1_user_name
            FROM (SELECT "user".id AS user_id, "user".name AS user_name
            FROM "user"
            WHERE "user".name LIKE :name_1) AS anon_1

        There are lots of cases where :meth:`_query.Query.from_self`
        may be useful.
        A simple one is where above, we may want to apply a row LIMIT to
        the set of user objects we query against, and then apply additional
        joins against that row-limited set::

            q = session.query(User).filter(User.name.like('e%')).\
                limit(5).from_self().\
                join(User.addresses).filter(Address.email.like('q%'))

        The above query joins to the ``Address`` entity but only against the
        first five results of the ``User`` query:

        .. sourcecode:: sql

            SELECT anon_1.user_id AS anon_1_user_id,
                   anon_1.user_name AS anon_1_user_name
            FROM (SELECT "user".id AS user_id, "user".name AS user_name
            FROM "user"
            WHERE "user".name LIKE :name_1
             LIMIT :param_1) AS anon_1
            JOIN address ON anon_1.user_id = address.user_id
            WHERE address.email LIKE :email_1

        **Automatic Aliasing**

        Another key behavior of :meth:`_query.Query.from_self`
        is that it applies
        **automatic aliasing** to the entities inside the subquery, when
        they are referenced on the outside.  Above, if we continue to
        refer to the ``User`` entity without any additional aliasing applied
        to it, those references will be in terms of the subquery::

            q = session.query(User).filter(User.name.like('e%')).\
                limit(5).from_self().\
                join(User.addresses).filter(Address.email.like('q%')).\
                order_by(User.name)

        The ORDER BY against ``User.name`` is aliased to be in terms of the
        inner subquery:

        .. sourcecode:: sql

            SELECT anon_1.user_id AS anon_1_user_id,
                   anon_1.user_name AS anon_1_user_name
            FROM (SELECT "user".id AS user_id, "user".name AS user_name
            FROM "user"
            WHERE "user".name LIKE :name_1
             LIMIT :param_1) AS anon_1
            JOIN address ON anon_1.user_id = address.user_id
            WHERE address.email LIKE :email_1 ORDER BY anon_1.user_name

        The automatic aliasing feature only works in a **limited** way,
        for simple filters and orderings.   More ambitious constructions
        such as referring to the entity in joins should prefer to use
        explicit subquery objects, typically making use of the
        :meth:`_query.Query.subquery`
        method to produce an explicit subquery object.
        Always test the structure of queries by viewing the SQL to ensure
        a particular structure does what's expected!

        **Changing the Entities**

        :meth:`_query.Query.from_self`
        also includes the ability to modify what
        columns are being queried.   In our example, we want ``User.id``
        to be queried by the inner query, so that we can join to the
        ``Address`` entity on the outside, but we only wanted the outer
        query to return the ``Address.email`` column::

            q = session.query(User).filter(User.name.like('e%')).\
                limit(5).from_self(Address.email).\
                join(User.addresses).filter(Address.email.like('q%'))

        yielding:

        .. sourcecode:: sql

            SELECT address.email AS address_email
            FROM (SELECT "user".id AS user_id, "user".name AS user_name
            FROM "user"
            WHERE "user".name LIKE :name_1
             LIMIT :param_1) AS anon_1
            JOIN address ON anon_1.user_id = address.user_id
            WHERE address.email LIKE :email_1

        **Looking out for Inner / Outer Columns**

        Keep in mind that when referring to columns that originate from
        inside the subquery, we need to ensure they are present in the
        columns clause of the subquery itself; this is an ordinary aspect of
        SQL.  For example, if we wanted to load from a joined entity inside
        the subquery using :func:`.contains_eager`, we need to add those
        columns.   Below illustrates a join of ``Address`` to ``User``,
        then a subquery, and then we'd like :func:`.contains_eager` to access
        the ``User`` columns::

            q = session.query(Address).join(Address.user).\
                filter(User.name.like('e%'))

            q = q.add_entity(User).from_self().\
                options(contains_eager(Address.user))

        We use :meth:`_query.Query.add_entity` above **before** we call
        :meth:`_query.Query.from_self`
        so that the ``User`` columns are present
        in the inner subquery, so that they are available to the
        :func:`.contains_eager` modifier we are using on the outside,
        producing:

        .. sourcecode:: sql

            SELECT anon_1.address_id AS anon_1_address_id,
                   anon_1.address_email AS anon_1_address_email,
                   anon_1.address_user_id AS anon_1_address_user_id,
                   anon_1.user_id AS anon_1_user_id,
                   anon_1.user_name AS anon_1_user_name
            FROM (
                SELECT address.id AS address_id,
                address.email AS address_email,
                address.user_id AS address_user_id,
                "user".id AS user_id,
                "user".name AS user_name
            FROM address JOIN "user" ON "user".id = address.user_id
            WHERE "user".name LIKE :name_1) AS anon_1

        If we didn't call ``add_entity(User)``, but still asked
        :func:`.contains_eager` to load the ``User`` entity, it would be
        forced to add the table on the outside without the correct
        join criteria - note the ``anon1, "user"`` phrase at
        the end:

        .. sourcecode:: sql

            -- incorrect query
            SELECT anon_1.address_id AS anon_1_address_id,
                   anon_1.address_email AS anon_1_address_email,
                   anon_1.address_user_id AS anon_1_address_user_id,
                   "user".id AS user_id,
                   "user".name AS user_name
            FROM (
                SELECT address.id AS address_id,
                address.email AS address_email,
                address.user_id AS address_user_id
            FROM address JOIN "user" ON "user".id = address.user_id
            WHERE "user".name LIKE :name_1) AS anon_1, "user"

        :param \*entities: optional list of entities which will replace
         those being selected.

        """
        return self._from_self(*entities)

    def _from_self(self, *entities):
        fromclause = (
            self.set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)
            .enable_eagerloads(False)
            .correlate(None)
            .subquery()
            ._anonymous_fromclause()
        )

        q = self._from_selectable(fromclause)

        if entities:
            q._set_entities(entities)
        return q

    @_generative
    def _set_enable_single_crit(self, val):
        self._compile_options += {"_enable_single_crit": val}

    @_generative
    def _from_selectable(self, fromclause, set_entity_from=True):
        for attr in (
            "_where_criteria",
            "_order_by_clauses",
            "_group_by_clauses",
            "_limit_clause",
            "_offset_clause",
            "_last_joined_entity",
            "_legacy_setup_joins",
            "_distinct",
            "_distinct_on",
            "_having_criteria",
            "_prefixes",
            "_suffixes",
        ):
            self.__dict__.pop(attr, None)
        self._set_select_from([fromclause], set_entity_from)
        self._compile_options += {
            "_enable_single_crit": False,
        }

        # this enables clause adaptation for non-ORM
        # expressions.
        # legacy.  see test/orm/test_froms.py for various
        # "oldstyle" tests that rely on this and the corresponding
        # "newtyle" that do not.
        self._compile_options += {"_orm_only_from_obj_alias": False}

    @util.deprecated(
        "1.4",
        ":meth:`_query.Query.values` "
        "is deprecated and will be removed in a "
        "future release.  Please use :meth:`_query.Query.with_entities`",
    )
    def values(self, *columns):
        """Return an iterator yielding result tuples corresponding
        to the given list of columns

        """

        if not columns:
            return iter(())
        q = self._clone().enable_eagerloads(False)
        q._set_entities(columns)
        if not q.load_options._yield_per:
            q.load_options += {"_yield_per": 10}
        return iter(q)

    _values = values

    @util.deprecated(
        "1.4",
        ":meth:`_query.Query.value` "
        "is deprecated and will be removed in a "
        "future release.  Please use :meth:`_query.Query.with_entities` "
        "in combination with :meth:`_query.Query.scalar`",
    )
    def value(self, column):
        """Return a scalar result corresponding to the given
        column expression.

        """
        try:
            return next(self.values(column))[0]
        except StopIteration:
            return None

    @_generative
    def with_entities(self, *entities):
        r"""Return a new :class:`_query.Query`
        replacing the SELECT list with the
        given entities.

        e.g.::

            # Users, filtered on some arbitrary criterion
            # and then ordered by related email address
            q = session.query(User).\
                        join(User.address).\
                        filter(User.name.like('%ed%')).\
                        order_by(Address.email)

            # given *only* User.id==5, Address.email, and 'q', what
            # would the *next* User in the result be ?
            subq = q.with_entities(Address.email).\
                        order_by(None).\
                        filter(User.id==5).\
                        subquery()
            q = q.join((subq, subq.c.email < Address.email)).\
                        limit(1)

        """
        self._set_entities(entities)

    @_generative
    def add_columns(self, *column):
        """Add one or more column expressions to the list
        of result columns to be returned."""

        self._raw_columns = list(self._raw_columns)

        self._raw_columns.extend(
            coercions.expect(
                roles.ColumnsClauseRole, c, apply_propagate_attrs=self
            )
            for c in column
        )

    @util.deprecated(
        "1.4",
        ":meth:`_query.Query.add_column` "
        "is deprecated and will be removed in a "
        "future release.  Please use :meth:`_query.Query.add_columns`",
    )
    def add_column(self, column):
        """Add a column expression to the list of result columns to be
        returned.

        """
        return self.add_columns(column)

    @_generative
    def options(self, *args):
        """Return a new :class:`_query.Query` object,
        applying the given list of
        mapper options.

        Most supplied options regard changing how column- and
        relationship-mapped attributes are loaded.

        .. seealso::

            :ref:`deferred_options`

            :ref:`relationship_loader_options`

        """

        opts = tuple(util.flatten_iterator(args))
        if self._compile_options._current_path:
            for opt in opts:
                if opt._is_legacy_option:
                    opt.process_query_conditionally(self)
        else:
            for opt in opts:
                if opt._is_legacy_option:
                    opt.process_query(self)

        self._with_options += opts

    def with_transformation(self, fn):
        """Return a new :class:`_query.Query` object transformed by
        the given function.

        E.g.::

            def filter_something(criterion):
                def transform(q):
                    return q.filter(criterion)
                return transform

            q = q.with_transformation(filter_something(x==5))

        This allows ad-hoc recipes to be created for :class:`_query.Query`
        objects.  See the example at :ref:`hybrid_transformers`.

        """
        return fn(self)

    def get_execution_options(self):
        """Get the non-SQL options which will take effect during execution.

        .. versionadded:: 1.3

        .. seealso::

            :meth:`_query.Query.execution_options`
        """
        return self._execution_options

    @_generative
    def execution_options(self, **kwargs):
        """Set non-SQL options which take effect during execution.

        Options allowed here include all of those accepted by
        :meth:`_engine.Connection.execution_options`, as well as a series
        of ORM specific options:

        ``populate_existing=True`` - equivalent to using
        :meth:`_orm.Query.populate_existing`

        ``autoflush=True|False`` - equivalent to using
        :meth:`_orm.Query.autoflush`

        ``yield_per=<value>`` - equivalent to using
        :meth:`_orm.Query.yield_per`

        Note that the ``stream_results`` execution option is enabled
        automatically if the :meth:`~sqlalchemy.orm.query.Query.yield_per()`
        method or execution option is used.

        The execution options may also be specified on a per execution basis
        when using :term:`2.0 style` queries via the
        :paramref:`_orm.Session.execution_options` parameter.

        .. versionadded:: 1.4 - added ORM options to
           :meth:`_orm.Query.execution_options`

        .. seealso::

            :ref:`engine_stream_results`

            :meth:`_query.Query.get_execution_options`

        """
        self._execution_options = self._execution_options.union(kwargs)

    @_generative
    def with_for_update(
        self,
        read=False,
        nowait=False,
        of=None,
        skip_locked=False,
        key_share=False,
    ):
        """return a new :class:`_query.Query`
        with the specified options for the
        ``FOR UPDATE`` clause.

        The behavior of this method is identical to that of
        :meth:`_expression.GenerativeSelect.with_for_update`.
        When called with no arguments,
        the resulting ``SELECT`` statement will have a ``FOR UPDATE`` clause
        appended.  When additional arguments are specified, backend-specific
        options such as ``FOR UPDATE NOWAIT`` or ``LOCK IN SHARE MODE``
        can take effect.

        E.g.::

            q = sess.query(User).populate_existing().with_for_update(nowait=True, of=User)

        The above query on a PostgreSQL backend will render like::

            SELECT users.id AS users_id FROM users FOR UPDATE OF users NOWAIT

        .. note::  It is generally a good idea to combine the use of the
           :meth:`_orm.Query.populate_existing` method when using the
           :meth:`_orm.Query.with_for_update` method.   The purpose of
           :meth:`_orm.Query.populate_existing` is to force all the data read
           from the SELECT to be populated into the ORM objects returned,
           even if these objects are already in the :term:`identity map`.

        .. seealso::

            :meth:`_expression.GenerativeSelect.with_for_update`
            - Core level method with
            full argument and behavioral description.

            :meth:`_orm.Query.populate_existing` - overwrites attributes of
            objects already loaded in the identity map.

        """  # noqa: E501

        self._for_update_arg = ForUpdateArg(
            read=read,
            nowait=nowait,
            of=of,
            skip_locked=skip_locked,
            key_share=key_share,
        )

    @_generative
    def params(self, *args, **kwargs):
        r"""Add values for bind parameters which may have been
        specified in filter().

        Parameters may be specified using \**kwargs, or optionally a single
        dictionary as the first positional argument. The reason for both is
        that \**kwargs is convenient, however some parameter dictionaries
        contain unicode keys in which case \**kwargs cannot be used.

        """
        if len(args) == 1:
            kwargs.update(args[0])
        elif len(args) > 0:
            raise sa_exc.ArgumentError(
                "params() takes zero or one positional argument, "
                "which is a dictionary."
            )
        self._params = self._params.union(kwargs)

    def where(self, *criterion):
        """A synonym for :meth:`.Query.filter`.

        .. versionadded:: 1.4

        """
        return self.filter(*criterion)

    @_generative
    @_assertions(_no_statement_condition, _no_limit_offset)
    def filter(self, *criterion):
        r"""Apply the given filtering criterion to a copy
        of this :class:`_query.Query`, using SQL expressions.

        e.g.::

            session.query(MyClass).filter(MyClass.name == 'some name')

        Multiple criteria may be specified as comma separated; the effect
        is that they will be joined together using the :func:`.and_`
        function::

            session.query(MyClass).\
                filter(MyClass.name == 'some name', MyClass.id > 5)

        The criterion is any SQL expression object applicable to the
        WHERE clause of a select.   String expressions are coerced
        into SQL expression constructs via the :func:`_expression.text`
        construct.

        .. seealso::

            :meth:`_query.Query.filter_by` - filter on keyword expressions.

        """
        for criterion in list(criterion):
            criterion = coercions.expect(
                roles.WhereHavingRole, criterion, apply_propagate_attrs=self
            )

            # legacy vvvvvvvvvvvvvvvvvvvvvvvvvvv
            if self._aliased_generation:
                criterion = sql_util._deep_annotate(
                    criterion, {"aliased_generation": self._aliased_generation}
                )
            # legacy ^^^^^^^^^^^^^^^^^^^^^^^^^^^

            self._where_criteria += (criterion,)

    @util.memoized_property
    def _last_joined_entity(self):
        if self._legacy_setup_joins:
            return _legacy_determine_last_joined_entity(
                self._legacy_setup_joins, self._entity_from_pre_ent_zero()
            )
        else:
            return None

    def _filter_by_zero(self):
        if self._legacy_setup_joins:
            _last_joined_entity = self._last_joined_entity
            if _last_joined_entity is not None:
                return _last_joined_entity

        if self._from_obj:
            return self._from_obj[0]

        return self._raw_columns[0]

    def filter_by(self, **kwargs):
        r"""Apply the given filtering criterion to a copy
        of this :class:`_query.Query`, using keyword expressions.

        e.g.::

            session.query(MyClass).filter_by(name = 'some name')

        Multiple criteria may be specified as comma separated; the effect
        is that they will be joined together using the :func:`.and_`
        function::

            session.query(MyClass).\
                filter_by(name = 'some name', id = 5)

        The keyword expressions are extracted from the primary
        entity of the query, or the last entity that was the
        target of a call to :meth:`_query.Query.join`.

        .. seealso::

            :meth:`_query.Query.filter` - filter on SQL expressions.

        """
        from_entity = self._filter_by_zero()
        if from_entity is None:
            raise sa_exc.InvalidRequestError(
                "Can't use filter_by when the first entity '%s' of a query "
                "is not a mapped class. Please use the filter method instead, "
                "or change the order of the entities in the query"
                % self._query_entity_zero()
            )

        clauses = [
            _entity_namespace_key(from_entity, key) == value
            for key, value in kwargs.items()
        ]
        return self.filter(*clauses)

    @_generative
    @_assertions(_no_statement_condition, _no_limit_offset)
    def order_by(self, *clauses):
        """Apply one or more ORDER BY criterion to the query and return
        the newly resulting :class:`_query.Query`.

        All existing ORDER BY settings can be suppressed by  passing
        ``None``.

        """

        if len(clauses) == 1 and (clauses[0] is None or clauses[0] is False):
            self._order_by_clauses = ()
        else:
            criterion = tuple(
                coercions.expect(roles.OrderByRole, clause)
                for clause in clauses
            )
            # legacy vvvvvvvvvvvvvvvvvvvvvvvvvvv
            if self._aliased_generation:
                criterion = tuple(
                    [
                        sql_util._deep_annotate(
                            o, {"aliased_generation": self._aliased_generation}
                        )
                        for o in criterion
                    ]
                )
            # legacy ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

            self._order_by_clauses += criterion

    @_generative
    @_assertions(_no_statement_condition, _no_limit_offset)
    def group_by(self, *clauses):
        """Apply one or more GROUP BY criterion to the query and return
        the newly resulting :class:`_query.Query`.

        All existing GROUP BY settings can be suppressed by
        passing ``None`` - this will suppress any GROUP BY configured
        on mappers as well.

        .. versionadded:: 1.1 GROUP BY can be cancelled by passing
           ``None``, in the same way as ORDER BY.

        """

        if len(clauses) == 1 and (clauses[0] is None or clauses[0] is False):
            self._group_by_clauses = ()
        else:
            criterion = tuple(
                coercions.expect(roles.GroupByRole, clause)
                for clause in clauses
            )
            # legacy vvvvvvvvvvvvvvvvvvvvvvvvvvv
            if self._aliased_generation:
                criterion = tuple(
                    [
                        sql_util._deep_annotate(
                            o, {"aliased_generation": self._aliased_generation}
                        )
                        for o in criterion
                    ]
                )
            # legacy ^^^^^^^^^^^^^^^^^^^^^^^^^^

            self._group_by_clauses += criterion

    @_generative
    @_assertions(_no_statement_condition, _no_limit_offset)
    def having(self, criterion):
        r"""Apply a HAVING criterion to the query and return the
        newly resulting :class:`_query.Query`.

        :meth:`_query.Query.having` is used in conjunction with
        :meth:`_query.Query.group_by`.

        HAVING criterion makes it possible to use filters on aggregate
        functions like COUNT, SUM, AVG, MAX, and MIN, eg.::

            q = session.query(User.id).\
                        join(User.addresses).\
                        group_by(User.id).\
                        having(func.count(Address.id) > 2)

        """

        self._having_criteria += (
            coercions.expect(
                roles.WhereHavingRole, criterion, apply_propagate_attrs=self
            ),
        )

    def _set_op(self, expr_fn, *q):
        return self._from_selectable(expr_fn(*([self] + list(q))).subquery())

    def union(self, *q):
        """Produce a UNION of this Query against one or more queries.

        e.g.::

            q1 = sess.query(SomeClass).filter(SomeClass.foo=='bar')
            q2 = sess.query(SomeClass).filter(SomeClass.bar=='foo')

            q3 = q1.union(q2)

        The method accepts multiple Query objects so as to control
        the level of nesting.  A series of ``union()`` calls such as::

            x.union(y).union(z).all()

        will nest on each ``union()``, and produces::

            SELECT * FROM (SELECT * FROM (SELECT * FROM X UNION
                            SELECT * FROM y) UNION SELECT * FROM Z)

        Whereas::

            x.union(y, z).all()

        produces::

            SELECT * FROM (SELECT * FROM X UNION SELECT * FROM y UNION
                            SELECT * FROM Z)

        Note that many database backends do not allow ORDER BY to
        be rendered on a query called within UNION, EXCEPT, etc.
        To disable all ORDER BY clauses including those configured
        on mappers, issue ``query.order_by(None)`` - the resulting
        :class:`_query.Query` object will not render ORDER BY within
        its SELECT statement.

        """
        return self._set_op(expression.union, *q)

    def union_all(self, *q):
        """Produce a UNION ALL of this Query against one or more queries.

        Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See
        that method for usage examples.

        """
        return self._set_op(expression.union_all, *q)

    def intersect(self, *q):
        """Produce an INTERSECT of this Query against one or more queries.

        Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See
        that method for usage examples.

        """
        return self._set_op(expression.intersect, *q)

    def intersect_all(self, *q):
        """Produce an INTERSECT ALL of this Query against one or more queries.

        Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See
        that method for usage examples.

        """
        return self._set_op(expression.intersect_all, *q)

    def except_(self, *q):
        """Produce an EXCEPT of this Query against one or more queries.

        Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See
        that method for usage examples.

        """
        return self._set_op(expression.except_, *q)

    def except_all(self, *q):
        """Produce an EXCEPT ALL of this Query against one or more queries.

        Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See
        that method for usage examples.

        """
        return self._set_op(expression.except_all, *q)

    def _next_aliased_generation(self):
        if "_aliased_generation_counter" not in self.__dict__:
            self._aliased_generation_counter = 0
        self._aliased_generation_counter += 1
        return self._aliased_generation_counter

    @_generative
    @_assertions(_no_statement_condition, _no_limit_offset)
    def join(self, target, *props, **kwargs):
        r"""Create a SQL JOIN against this :class:`_query.Query`
        object's criterion
        and apply generatively, returning the newly resulting
        :class:`_query.Query`.

        **Simple Relationship Joins**

        Consider a mapping between two classes ``User`` and ``Address``,
        with a relationship ``User.addresses`` representing a collection
        of ``Address`` objects associated with each ``User``.   The most
        common usage of :meth:`_query.Query.join`
        is to create a JOIN along this
        relationship, using the ``User.addresses`` attribute as an indicator
        for how this should occur::

            q = session.query(User).join(User.addresses)

        Where above, the call to :meth:`_query.Query.join` along
        ``User.addresses`` will result in SQL approximately equivalent to::

            SELECT user.id, user.name
            FROM user JOIN address ON user.id = address.user_id

        In the above example we refer to ``User.addresses`` as passed to
        :meth:`_query.Query.join` as the "on clause", that is, it indicates
        how the "ON" portion of the JOIN should be constructed.

        To construct a chain of joins, multiple :meth:`_query.Query.join`
        calls may be used.  The relationship-bound attribute implies both
        the left and right side of the join at once::

            q = session.query(User).\
                    join(User.orders).\
                    join(Order.items).\
                    join(Item.keywords)

        .. note:: as seen in the above example, **the order in which each
           call to the join() method occurs is important**.    Query would not,
           for example, know how to join correctly if we were to specify
           ``User``, then ``Item``, then ``Order``, in our chain of joins; in
           such a case, depending on the arguments passed, it may raise an
           error that it doesn't know how to join, or it may produce invalid
           SQL in which case the database will raise an error. In correct
           practice, the
           :meth:`_query.Query.join` method is invoked in such a way that lines
           up with how we would want the JOIN clauses in SQL to be
           rendered, and each call should represent a clear link from what
           precedes it.

        **Joins to a Target Entity or Selectable**

        A second form of :meth:`_query.Query.join` allows any mapped entity or
        core selectable construct as a target.   In this usage,
        :meth:`_query.Query.join` will attempt to create a JOIN along the
        natural foreign key relationship between two entities::

            q = session.query(User).join(Address)

        In the above calling form, :meth:`_query.Query.join` is called upon to
        create the "on clause" automatically for us.  This calling form will
        ultimately raise an error if either there are no foreign keys between
        the two entities, or if there are multiple foreign key linkages between
        the target entity and the entity or entities already present on the
        left side such that creating a join requires more information.  Note
        that when indicating a join to a target without any ON clause, ORM
        configured relationships are not taken into account.

        **Joins to a Target with an ON Clause**

        The third calling form allows both the target entity as well
        as the ON clause to be passed explicitly.    A example that includes
        a SQL expression as the ON clause is as follows::

            q = session.query(User).join(Address, User.id==Address.user_id)

        The above form may also use a relationship-bound attribute as the
        ON clause as well::

            q = session.query(User).join(Address, User.addresses)

        The above syntax can be useful for the case where we wish
        to join to an alias of a particular target entity.  If we wanted
        to join to ``Address`` twice, it could be achieved using two
        aliases set up using the :func:`~sqlalchemy.orm.aliased` function::

            a1 = aliased(Address)
            a2 = aliased(Address)

            q = session.query(User).\
                    join(a1, User.addresses).\
                    join(a2, User.addresses).\
                    filter(a1.email_address=='ed@foo.com').\
                    filter(a2.email_address=='ed@bar.com')

        The relationship-bound calling form can also specify a target entity
        using the :meth:`_orm.PropComparator.of_type` method; a query
        equivalent to the one above would be::

            a1 = aliased(Address)
            a2 = aliased(Address)

            q = session.query(User).\
                    join(User.addresses.of_type(a1)).\
                    join(User.addresses.of_type(a2)).\
                    filter(a1.email_address == 'ed@foo.com').\
                    filter(a2.email_address == 'ed@bar.com')

        **Augmenting Built-in ON Clauses**

        As a substitute for providing a full custom ON condition for an
        existing relationship, the :meth:`_orm.PropComparator.and_` function
        may be applied to a relationship attribute to augment additional
        criteria into the ON clause; the additional criteria will be combined
        with the default criteria using AND::

            q = session.query(User).join(
                User.addresses.and_(Address.email_address != 'foo@bar.com')
            )

        .. versionadded:: 1.4

        **Joining to Tables and Subqueries**


        The target of a join may also be any table or SELECT statement,
        which may be related to a target entity or not.   Use the
        appropriate ``.subquery()`` method in order to make a subquery
        out of a query::

            subq = session.query(Address).\
                filter(Address.email_address == 'ed@foo.com').\
                subquery()


            q = session.query(User).join(
                subq, User.id == subq.c.user_id
            )

        Joining to a subquery in terms of a specific relationship and/or
        target entity may be achieved by linking the subquery to the
        entity using :func:`_orm.aliased`::

            subq = session.query(Address).\
                filter(Address.email_address == 'ed@foo.com').\
                subquery()

            address_subq = aliased(Address, subq)

            q = session.query(User).join(
                User.addresses.of_type(address_subq)
            )


        **Controlling what to Join From**

        In cases where the left side of the current state of
        :class:`_query.Query` is not in line with what we want to join from,
        the :meth:`_query.Query.select_from` method may be used::

            q = session.query(Address).select_from(User).\
                            join(User.addresses).\
                            filter(User.name == 'ed')

        Which will produce SQL similar to::

            SELECT address.* FROM user
                JOIN address ON user.id=address.user_id
                WHERE user.name = :name_1

        **Legacy Features of Query.join()**

        .. deprecated:: 1.4 The following features are deprecated and will
           be removed in SQLAlchemy 2.0.

        The :meth:`_query.Query.join` method currently supports several
        usage patterns and arguments that are considered to be legacy
        as of SQLAlchemy 1.3.   A deprecation path will follow
        in the 1.4 series for the following features:


        * Joining on relationship names rather than attributes::

            session.query(User).join("addresses")

          **Why it's legacy**: the string name does not provide enough context
          for :meth:`_query.Query.join` to always know what is desired,
          notably in that there is no indication of what the left side
          of the join should be.  This gives rise to flags like
          ``from_joinpoint`` as well as the ability to place several
          join clauses in a single :meth:`_query.Query.join` call
          which don't solve the problem fully while also
          adding new calling styles that are unnecessary and expensive to
          accommodate internally.

          **Modern calling pattern**:  Use the actual relationship,
          e.g. ``User.addresses`` in the above case::

              session.query(User).join(User.addresses)

        * Automatic aliasing with the ``aliased=True`` flag::

            session.query(Node).join(Node.children, aliased=True).\
                filter(Node.name == 'some name')

          **Why it's legacy**:  the automatic aliasing feature of
          :class:`_query.Query` is intensely complicated, both in its internal
          implementation as well as in its observed behavior, and is almost
          never used.  It is difficult to know upon inspection where and when
          its aliasing of a target entity, ``Node`` in the above case, will be
          applied and when it won't, and additionally the feature has to use
          very elaborate heuristics to achieve this implicit behavior.

          **Modern calling pattern**: Use the :func:`_orm.aliased` construct
          explicitly::

            from sqlalchemy.orm import aliased

            n1 = aliased(Node)

            session.query(Node).join(Node.children.of_type(n1)).\
                filter(n1.name == 'some name')

        * Multiple joins in one call::

            session.query(User).join("orders", "items")

            session.query(User).join(User.orders, Order.items)

            session.query(User).join(
                (Order, User.orders),
                (Item, Item.order_id == Order.id)
            )

            # ... and several more forms actually

          **Why it's legacy**: being able to chain multiple ON clauses in one
          call to :meth:`_query.Query.join` is yet another attempt to solve
          the problem of being able to specify what entity to join from,
          and is the source of a large variety of potential calling patterns
          that are internally expensive and complicated to parse and
          accommodate.

          **Modern calling pattern**:  Use relationship-bound attributes
          or SQL-oriented ON clauses within separate calls, so that
          each call to :meth:`_query.Query.join` knows what the left
          side should be::

            session.query(User).join(User.orders).join(
                Item, Item.order_id == Order.id)


        :param \*props: Incoming arguments for :meth:`_query.Query.join`,
         the props collection in modern use should be considered to be a  one
         or two argument form, either as a single "target" entity or ORM
         attribute-bound relationship, or as a target entity plus an "on
         clause" which  may be a SQL expression or ORM attribute-bound
         relationship.

        :param isouter=False: If True, the join used will be a left outer join,
         just as if the :meth:`_query.Query.outerjoin` method were called.

        :param full=False: render FULL OUTER JOIN; implies ``isouter``.

         .. versionadded:: 1.1

        :param from_joinpoint=False: When using ``aliased=True``, a setting
         of True here will cause the join to be from the most recent
         joined target, rather than starting back from the original
         FROM clauses of the query.

         .. note:: This flag is considered legacy.

        :param aliased=False: If True, indicate that the JOIN target should be
         anonymously aliased.  Subsequent calls to :meth:`_query.Query.filter`
         and similar will adapt the incoming criterion to the target
         alias, until :meth:`_query.Query.reset_joinpoint` is called.

         .. note:: This flag is considered legacy.

        .. seealso::

            :ref:`ormtutorial_joins` in the ORM tutorial.

            :ref:`inheritance_toplevel` for details on how
            :meth:`_query.Query.join` is used for inheritance relationships.

            :func:`_orm.join` - a standalone ORM-level join function,
            used internally by :meth:`_query.Query.join`, which in previous
            SQLAlchemy versions was the primary ORM-level joining interface.

        """

        aliased, from_joinpoint, isouter, full = (
            kwargs.pop("aliased", False),
            kwargs.pop("from_joinpoint", False),
            kwargs.pop("isouter", False),
            kwargs.pop("full", False),
        )

        if aliased or from_joinpoint:
            util.warn_deprecated_20(
                "The ``aliased`` and ``from_joinpoint`` keyword arguments "
                "to Query.join() are deprecated and will be removed "
                "in SQLAlchemy 2.0."
            )

        if kwargs:
            raise TypeError(
                "unknown arguments: %s" % ", ".join(sorted(kwargs))
            )

        # legacy vvvvvvvvvvvvvvvvvvvvvvvvvvv
        if not from_joinpoint:
            self._last_joined_entity = None
            self._aliased_generation = None
        # legacy ^^^^^^^^^^^^^^^^^^^^^^^^^^^

        if props:
            onclause, legacy = props[0], props[1:]
        else:
            onclause = legacy = None

        if not legacy and onclause is None and not isinstance(target, tuple):
            # non legacy argument form
            _props = [(target,)]
        elif not legacy and isinstance(
            target,
            (expression.Selectable, type, AliasedClass, types.FunctionType),
        ):
            # non legacy argument form
            _props = [(target, onclause)]
        else:
            # legacy forms.   more time consuming :)
            _props = []
            _single = []
            for prop in (target,) + props:
                if isinstance(prop, tuple):
                    util.warn_deprecated_20(
                        "Query.join() will no longer accept tuples as "
                        "arguments in SQLAlchemy 2.0."
                    )
                    if _single:
                        _props.extend((_s,) for _s in _single)
                    _single = []

                    # this checks for an extremely ancient calling form of
                    # reversed tuples.
                    if isinstance(prop[0], (str, interfaces.PropComparator)):
                        prop = (prop[1], prop[0])

                    _props.append(prop)
                else:
                    _single.append(prop)
            if _single:
                _props.extend((_s,) for _s in _single)

        # legacy vvvvvvvvvvvvvvvvvvvvvvvvvvv
        if aliased:
            self._aliased_generation = self._next_aliased_generation()

        if self._aliased_generation:
            _props = [
                (
                    prop[0],
                    sql_util._deep_annotate(
                        prop[1],
                        {"aliased_generation": self._aliased_generation},
                    )
                    if isinstance(prop[1], expression.ClauseElement)
                    else prop[1],
                )
                if len(prop) == 2
                else prop
                for prop in _props
            ]

        # legacy ^^^^^^^^^^^^^^^^^^^^^^^^^^^

        joins_to_add = tuple(
            (
                coercions.expect(
                    roles.JoinTargetRole,
                    prop[0],
                    legacy=True,
                    apply_propagate_attrs=self,
                ),
                (
                    coercions.expect(roles.OnClauseRole, prop[1], legacy=True)
                    #                    if not isinstance(prop[1], str)
                    #                    else prop[1]
                )
                if len(prop) == 2
                else None,
                None,
                {
                    "isouter": isouter,
                    "aliased": aliased,
                    "from_joinpoint": True if i > 0 else from_joinpoint,
                    "full": full,
                    "aliased_generation": self._aliased_generation,
                },
            )
            for i, prop in enumerate(_props)
        )

        if len(joins_to_add) > 1:
            util.warn_deprecated_20(
                "Passing a chain of multiple join conditions to Query.join() "
                "is deprecated and will be removed in SQLAlchemy 2.0. "
                "Please use individual join() calls per relationship."
            )

        self._legacy_setup_joins += joins_to_add

        self.__dict__.pop("_last_joined_entity", None)

    def outerjoin(self, target, *props, **kwargs):
        """Create a left outer join against this ``Query`` object's criterion
        and apply generatively, returning the newly resulting ``Query``.

        Usage is the same as the ``join()`` method.

        """
        kwargs["isouter"] = True
        return self.join(target, *props, **kwargs)

    @_generative
    @_assertions(_no_statement_condition)
    def reset_joinpoint(self):
        """Return a new :class:`.Query`, where the "join point" has
        been reset back to the base FROM entities of the query.

        This method is usually used in conjunction with the
        ``aliased=True`` feature of the :meth:`~.Query.join`
        method.  See the example in :meth:`~.Query.join` for how
        this is used.

        """
        self._last_joined_entity = None
        self._aliased_generation = None

    @_generative
    @_assertions(_no_clauseelement_condition)
    def select_from(self, *from_obj):
        r"""Set the FROM clause of this :class:`.Query` explicitly.

        :meth:`.Query.select_from` is often used in conjunction with
        :meth:`.Query.join` in order to control which entity is selected
        from on the "left" side of the join.

        The entity or selectable object here effectively replaces the
        "left edge" of any calls to :meth:`~.Query.join`, when no
        joinpoint is otherwise established - usually, the default "join
        point" is the leftmost entity in the :class:`~.Query` object's
        list of entities to be selected.

        A typical example::

            q = session.query(Address).select_from(User).\
                join(User.addresses).\
                filter(User.name == 'ed')

        Which produces SQL equivalent to::

            SELECT address.* FROM user
            JOIN address ON user.id=address.user_id
            WHERE user.name = :name_1

        :param \*from_obj: collection of one or more entities to apply
         to the FROM clause.  Entities can be mapped classes,
         :class:`.AliasedClass` objects, :class:`.Mapper` objects
         as well as core :class:`.FromClause` elements like subqueries.

        .. versionchanged:: 0.9
            This method no longer applies the given FROM object
            to be the selectable from which matching entities
            select from; the :meth:`.select_entity_from` method
            now accomplishes this.  See that method for a description
            of this behavior.

        .. seealso::

            :meth:`~.Query.join`

            :meth:`.Query.select_entity_from`

        """

        self._set_select_from(from_obj, False)

    @util.deprecated_20(
        ":meth:`_orm.Query.select_entity_from`",
        alternative="Use the :func:`_orm.aliased` construct instead",
    )
    @_generative
    @_assertions(_no_clauseelement_condition)
    def select_entity_from(self, from_obj):
        r"""Set the FROM clause of this :class:`_query.Query` to a
        core selectable, applying it as a replacement FROM clause
        for corresponding mapped entities.

        The :meth:`_query.Query.select_entity_from`
        method supplies an alternative
        approach to the use case of applying an :func:`.aliased` construct
        explicitly throughout a query.  Instead of referring to the
        :func:`.aliased` construct explicitly,
        :meth:`_query.Query.select_entity_from` automatically *adapts* all
        occurrences of the entity to the target selectable.

        Given a case for :func:`.aliased` such as selecting ``User``
        objects from a SELECT statement::

            select_stmt = select(User).where(User.id == 7)
            user_alias = aliased(User, select_stmt)

            q = session.query(user_alias).\
                filter(user_alias.name == 'ed')

        Above, we apply the ``user_alias`` object explicitly throughout the
        query.  When it's not feasible for ``user_alias`` to be referenced
        explicitly in many places, :meth:`_query.Query.select_entity_from`
        may be
        used at the start of the query to adapt the existing ``User`` entity::

            q = session.query(User).\
                select_entity_from(select_stmt.subquery()).\
                filter(User.name == 'ed')

        Above, the generated SQL will show that the ``User`` entity is
        adapted to our statement, even in the case of the WHERE clause:

        .. sourcecode:: sql

            SELECT anon_1.id AS anon_1_id, anon_1.name AS anon_1_name
            FROM (SELECT "user".id AS id, "user".name AS name
            FROM "user"
            WHERE "user".id = :id_1) AS anon_1
            WHERE anon_1.name = :name_1

        The :meth:`_query.Query.select_entity_from` method is similar to the
        :meth:`_query.Query.select_from` method,
        in that it sets the FROM clause
        of the query.  The difference is that it additionally applies
        adaptation to the other parts of the query that refer to the
        primary entity.  If above we had used :meth:`_query.Query.select_from`
        instead, the SQL generated would have been:

        .. sourcecode:: sql

            -- uses plain select_from(), not select_entity_from()
            SELECT "user".id AS user_id, "user".name AS user_name
            FROM "user", (SELECT "user".id AS id, "user".name AS name
            FROM "user"
            WHERE "user".id = :id_1) AS anon_1
            WHERE "user".name = :name_1

        To supply textual SQL to the :meth:`_query.Query.select_entity_from`
        method,
        we can make use of the :func:`_expression.text` construct.  However,
        the
        :func:`_expression.text`
        construct needs to be aligned with the columns of our
        entity, which is achieved by making use of the
        :meth:`_expression.TextClause.columns` method::

            text_stmt = text("select id, name from user").columns(
                User.id, User.name).subquery()
            q = session.query(User).select_entity_from(text_stmt)

        :meth:`_query.Query.select_entity_from` itself accepts an
        :func:`.aliased`
        object, so that the special options of :func:`.aliased` such as
        :paramref:`.aliased.adapt_on_names` may be used within the
        scope of the :meth:`_query.Query.select_entity_from`
        method's adaptation
        services.  Suppose
        a view ``user_view`` also returns rows from ``user``.    If
        we reflect this view into a :class:`_schema.Table`, this view has no
        relationship to the :class:`_schema.Table` to which we are mapped,
        however
        we can use name matching to select from it::

            user_view = Table('user_view', metadata,
                              autoload_with=engine)
            user_view_alias = aliased(
                User, user_view, adapt_on_names=True)
            q = session.query(User).\
                select_entity_from(user_view_alias).\
                order_by(User.name)

        .. versionchanged:: 1.1.7 The :meth:`_query.Query.select_entity_from`
           method now accepts an :func:`.aliased` object as an alternative
           to a :class:`_expression.FromClause` object.

        :param from_obj: a :class:`_expression.FromClause`
         object that will replace
         the FROM clause of this :class:`_query.Query`.
         It also may be an instance
         of :func:`.aliased`.



        .. seealso::

            :meth:`_query.Query.select_from`

        """

        self._set_select_from([from_obj], True)
        self._compile_options += {"_enable_single_crit": False}

    def __getitem__(self, item):
        return orm_util._getitem(
            self,
            item,
            allow_negative=not self.session or not self.session.future,
        )

    @_generative
    @_assertions(_no_statement_condition)
    def slice(self, start, stop):
        """Computes the "slice" of the :class:`_query.Query` represented by
        the given indices and returns the resulting :class:`_query.Query`.

        The start and stop indices behave like the argument to Python's
        built-in :func:`range` function. This method provides an
        alternative to using ``LIMIT``/``OFFSET`` to get a slice of the
        query.

        For example, ::

            session.query(User).order_by(User.id).slice(1, 3)

        renders as

        .. sourcecode:: sql

           SELECT users.id AS users_id,
                  users.name AS users_name
           FROM users ORDER BY users.id
           LIMIT ? OFFSET ?
           (2, 1)

        .. seealso::

           :meth:`_query.Query.limit`

           :meth:`_query.Query.offset`

        """

        self._limit_clause, self._offset_clause = sql_util._make_slice(
            self._limit_clause, self._offset_clause, start, stop
        )

    @_generative
    @_assertions(_no_statement_condition)
    def limit(self, limit):
        """Apply a ``LIMIT`` to the query and return the newly resulting
        ``Query``.

        """
        self._limit_clause = sql_util._offset_or_limit_clause(limit)

    @_generative
    @_assertions(_no_statement_condition)
    def offset(self, offset):
        """Apply an ``OFFSET`` to the query and return the newly resulting
        ``Query``.

        """
        self._offset_clause = sql_util._offset_or_limit_clause(offset)

    @_generative
    @_assertions(_no_statement_condition)
    def distinct(self, *expr):
        r"""Apply a ``DISTINCT`` to the query and return the newly resulting
        ``Query``.


        .. note::

            The ORM-level :meth:`.distinct` call includes logic that will
            automatically add columns from the ORDER BY of the query to the
            columns clause of the SELECT statement, to satisfy the common need
            of the database backend that ORDER BY columns be part of the SELECT
            list when DISTINCT is used.   These columns *are not* added to the
            list of columns actually fetched by the :class:`_query.Query`,
            however,
            so would not affect results. The columns are passed through when
            using the :attr:`_query.Query.statement` accessor, however.

            .. deprecated:: 2.0  This logic is deprecated and will be removed
               in SQLAlchemy 2.0.     See :ref:`migration_20_query_distinct`
               for a description of this use case in 2.0.

        :param \*expr: optional column expressions.  When present,
         the PostgreSQL dialect will render a ``DISTINCT ON (<expressions>)``
         construct.

         .. deprecated:: 1.4 Using \*expr in other dialects is deprecated
            and will raise :class:`_exc.CompileError` in a future version.

        """
        if expr:
            self._distinct = True
            self._distinct_on = self._distinct_on + tuple(
                coercions.expect(roles.ByOfRole, e) for e in expr
            )
        else:
            self._distinct = True

    def all(self):
        """Return the results represented by this :class:`_query.Query`
        as a list.

        This results in an execution of the underlying SQL statement.

        .. warning::  The :class:`_query.Query` object,
           when asked to return either
           a sequence or iterator that consists of full ORM-mapped entities,
           will **deduplicate entries based on primary key**.  See the FAQ for
           more details.

            .. seealso::

                :ref:`faq_query_deduplicating`
        """
        return self._iter().all()

    @_generative
    @_assertions(_no_clauseelement_condition)
    def from_statement(self, statement):
        """Execute the given SELECT statement and return results.

        This method bypasses all internal statement compilation, and the
        statement is executed without modification.

        The statement is typically either a :func:`_expression.text`
        or :func:`_expression.select` construct, and should return the set
        of columns
        appropriate to the entity class represented by this
        :class:`_query.Query`.

        .. seealso::

            :ref:`orm_tutorial_literal_sql` - usage examples in the
            ORM tutorial

        """
        statement = coercions.expect(
            roles.SelectStatementRole, statement, apply_propagate_attrs=self
        )
        self._statement = statement

    def first(self):
        """Return the first result of this ``Query`` or
        None if the result doesn't contain any row.

        first() applies a limit of one within the generated SQL, so that
        only one primary entity row is generated on the server side
        (note this may consist of multiple result rows if join-loaded
        collections are present).

        Calling :meth:`_query.Query.first`
        results in an execution of the underlying
        query.

        .. seealso::

            :meth:`_query.Query.one`

            :meth:`_query.Query.one_or_none`

        """
        # replicates limit(1) behavior
        if self._statement is not None:
            return self._iter().first()
        else:
            return self.limit(1)._iter().first()

    def one_or_none(self):
        """Return at most one result or raise an exception.

        Returns ``None`` if the query selects
        no rows.  Raises ``sqlalchemy.orm.exc.MultipleResultsFound``
        if multiple object identities are returned, or if multiple
        rows are returned for a query that returns only scalar values
        as opposed to full identity-mapped entities.

        Calling :meth:`_query.Query.one_or_none`
        results in an execution of the
        underlying query.

        .. versionadded:: 1.0.9

            Added :meth:`_query.Query.one_or_none`

        .. seealso::

            :meth:`_query.Query.first`

            :meth:`_query.Query.one`

        """
        return self._iter().one_or_none()

    def one(self):
        """Return exactly one result or raise an exception.

        Raises ``sqlalchemy.orm.exc.NoResultFound`` if the query selects
        no rows.  Raises ``sqlalchemy.orm.exc.MultipleResultsFound``
        if multiple object identities are returned, or if multiple
        rows are returned for a query that returns only scalar values
        as opposed to full identity-mapped entities.

        Calling :meth:`.one` results in an execution of the underlying query.

        .. seealso::

            :meth:`_query.Query.first`

            :meth:`_query.Query.one_or_none`

        """
        return self._iter().one()

    def scalar(self):
        """Return the first element of the first result or None
        if no rows present.  If multiple rows are returned,
        raises MultipleResultsFound.

          >>> session.query(Item).scalar()
          <Item>
          >>> session.query(Item.id).scalar()
          1
          >>> session.query(Item.id).filter(Item.id < 0).scalar()
          None
          >>> session.query(Item.id, Item.name).scalar()
          1
          >>> session.query(func.count(Parent.id)).scalar()
          20

        This results in an execution of the underlying query.

        """
        # TODO: not sure why we can't use result.scalar() here
        try:
            ret = self.one()
            if not isinstance(ret, collections_abc.Sequence):
                return ret
            return ret[0]
        except orm_exc.NoResultFound:
            return None

    def __iter__(self):
        return self._iter().__iter__()

    def _iter(self):
        # new style execution.
        params = self._params

        statement = self._statement_20()
        result = self.session.execute(
            statement,
            params,
            execution_options={"_sa_orm_load_options": self.load_options},
        )

        # legacy: automatically set scalars, unique
        if result._attributes.get("is_single_entity", False):
            result = result.scalars()

        if result._attributes.get("filtered", False):
            result = result.unique()

        return result

    def __str__(self):
        statement = self._statement_20()

        try:
            bind = (
                self._get_bind_args(statement, self.session.get_bind)
                if self.session
                else None
            )
        except sa_exc.UnboundExecutionError:
            bind = None

        return str(statement.compile(bind))

    def _get_bind_args(self, statement, fn, **kw):
        return fn(clause=statement, **kw)

    @property
    def column_descriptions(self):
        """Return metadata about the columns which would be
        returned by this :class:`_query.Query`.

        Format is a list of dictionaries::

            user_alias = aliased(User, name='user2')
            q = sess.query(User, User.id, user_alias)

            # this expression:
            q.column_descriptions

            # would return:
            [
                {
                    'name':'User',
                    'type':User,
                    'aliased':False,
                    'expr':User,
                    'entity': User
                },
                {
                    'name':'id',
                    'type':Integer(),
                    'aliased':False,
                    'expr':User.id,
                    'entity': User
                },
                {
                    'name':'user2',
                    'type':User,
                    'aliased':True,
                    'expr':user_alias,
                    'entity': user_alias
                }
            ]

        """

        return _column_descriptions(self, legacy=True)

    def instances(self, result_proxy, context=None):
        """Return an ORM result given a :class:`_engine.CursorResult` and
        :class:`.QueryContext`.

        """
        if context is None:
            util.warn_deprecated(
                "Using the Query.instances() method without a context "
                "is deprecated and will be disallowed in a future release.  "
                "Please make use of :meth:`_query.Query.from_statement` "
                "for linking ORM results to arbitrary select constructs.",
                version="1.4",
            )
            compile_state = self._compile_state(for_statement=False)

            context = QueryContext(
                compile_state,
                compile_state.statement,
                self._params,
                self.session,
                self.load_options,
            )

        result = loading.instances(result_proxy, context)

        # legacy: automatically set scalars, unique
        if result._attributes.get("is_single_entity", False):
            result = result.scalars()

        if result._attributes.get("filtered", False):
            result = result.unique()

        return result

    def merge_result(self, iterator, load=True):
        """Merge a result into this :class:`_query.Query` object's Session.

        Given an iterator returned by a :class:`_query.Query`
        of the same structure
        as this one, return an identical iterator of results, with all mapped
        instances merged into the session using :meth:`.Session.merge`. This
        is an optimized method which will merge all mapped instances,
        preserving the structure of the result rows and unmapped columns with
        less method overhead than that of calling :meth:`.Session.merge`
        explicitly for each value.

        The structure of the results is determined based on the column list of
        this :class:`_query.Query` - if these do not correspond,
        unchecked errors
        will occur.

        The 'load' argument is the same as that of :meth:`.Session.merge`.

        For an example of how :meth:`_query.Query.merge_result` is used, see
        the source code for the example :ref:`examples_caching`, where
        :meth:`_query.Query.merge_result` is used to efficiently restore state
        from a cache back into a target :class:`.Session`.

        """

        return loading.merge_result(self, iterator, load)

    def exists(self):
        """A convenience method that turns a query into an EXISTS subquery
        of the form EXISTS (SELECT 1 FROM ... WHERE ...).

        e.g.::

            q = session.query(User).filter(User.name == 'fred')
            session.query(q.exists())

        Producing SQL similar to::

            SELECT EXISTS (
                SELECT 1 FROM users WHERE users.name = :name_1
            ) AS anon_1

        The EXISTS construct is usually used in the WHERE clause::

            session.query(User.id).filter(q.exists()).scalar()

        Note that some databases such as SQL Server don't allow an
        EXISTS expression to be present in the columns clause of a
        SELECT.    To select a simple boolean value based on the exists
        as a WHERE, use :func:`.literal`::

            from sqlalchemy import literal

            session.query(literal(True)).filter(q.exists()).scalar()

        """

        # .add_columns() for the case that we are a query().select_from(X),
        # so that ".statement" can be produced (#2995) but also without
        # omitting the FROM clause from a query(X) (#2818);
        # .with_only_columns() after we have a core select() so that
        # we get just "SELECT 1" without any entities.

        inner = (
            self.enable_eagerloads(False)
            .add_columns(sql.literal_column("1"))
            .set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)
            .statement.with_only_columns(1)
        )

        ezero = self._entity_from_pre_ent_zero()
        if ezero is not None:
            inner = inner.select_from(ezero)

        return sql.exists(inner)

    def count(self):
        r"""Return a count of rows this the SQL formed by this :class:`Query`
        would return.

        This generates the SQL for this Query as follows::

            SELECT count(1) AS count_1 FROM (
                SELECT <rest of query follows...>
            ) AS anon_1

        The above SQL returns a single row, which is the aggregate value
        of the count function; the :meth:`_query.Query.count`
        method then returns
        that single integer value.

        .. warning::

            It is important to note that the value returned by
            count() is **not the same as the number of ORM objects that this
            Query would return from a method such as the .all() method**.
            The :class:`_query.Query` object,
            when asked to return full entities,
            will **deduplicate entries based on primary key**, meaning if the
            same primary key value would appear in the results more than once,
            only one object of that primary key would be present.  This does
            not apply to a query that is against individual columns.

            .. seealso::

                :ref:`faq_query_deduplicating`

                :ref:`orm_tutorial_query_returning`

        For fine grained control over specific columns to count, to skip the
        usage of a subquery or otherwise control of the FROM clause, or to use
        other aggregate functions, use :attr:`~sqlalchemy.sql.expression.func`
        expressions in conjunction with :meth:`~.Session.query`, i.e.::

            from sqlalchemy import func

            # count User records, without
            # using a subquery.
            session.query(func.count(User.id))

            # return count of user "id" grouped
            # by "name"
            session.query(func.count(User.id)).\
                    group_by(User.name)

            from sqlalchemy import distinct

            # count distinct "name" values
            session.query(func.count(distinct(User.name)))

        """
        col = sql.func.count(sql.literal_column("*"))
        return self._from_self(col).scalar()

    def delete(self, synchronize_session="evaluate"):
        r"""Perform a DELETE with an arbitrary WHERE clause.

        Deletes rows matched by this query from the database.

        E.g.::

            sess.query(User).filter(User.age == 25).\
                delete(synchronize_session=False)

            sess.query(User).filter(User.age == 25).\
                delete(synchronize_session='evaluate')

        .. warning::

            See the section :ref:`orm_expression_update_delete` for important
            caveats and warnings, including limitations when using bulk UPDATE
            and DELETE with mapper inheritance configurations.

        :param synchronize_session: chooses the strategy to update the
         attributes on objects in the session.   See the section
         :ref:`orm_expression_update_delete` for a discussion of these
         strategies.

        :return: the count of rows matched as returned by the database's
          "row count" feature.

        .. seealso::

            :ref:`orm_expression_update_delete`

        """

        bulk_del = BulkDelete(self)
        if self.dispatch.before_compile_delete:
            for fn in self.dispatch.before_compile_delete:
                new_query = fn(bulk_del.query, bulk_del)
                if new_query is not None:
                    bulk_del.query = new_query

                self = bulk_del.query

        delete_ = sql.delete(*self._raw_columns)
        delete_._where_criteria = self._where_criteria
        result = self.session.execute(
            delete_,
            self._params,
            execution_options={"synchronize_session": synchronize_session},
        )
        bulk_del.result = result
        self.session.dispatch.after_bulk_delete(bulk_del)
        result.close()

        return result.rowcount

    def update(self, values, synchronize_session="evaluate", update_args=None):
        r"""Perform an UPDATE with an arbitrary WHERE clause.

        Updates rows matched by this query in the database.

        E.g.::

            sess.query(User).filter(User.age == 25).\
                update({User.age: User.age - 10}, synchronize_session=False)

            sess.query(User).filter(User.age == 25).\
                update({"age": User.age - 10}, synchronize_session='evaluate')

        .. warning::

            See the section :ref:`orm_expression_update_delete` for important
            caveats and warnings, including limitations when using arbitrary
            UPDATE and DELETE with mapper inheritance configurations.

        :param values: a dictionary with attributes names, or alternatively
         mapped attributes or SQL expressions, as keys, and literal
         values or sql expressions as values.   If :ref:`parameter-ordered
         mode <updates_order_parameters>` is desired, the values can be
         passed as a list of 2-tuples;
         this requires that the
         :paramref:`~sqlalchemy.sql.expression.update.preserve_parameter_order`
         flag is passed to the :paramref:`.Query.update.update_args` dictionary
         as well.

        :param synchronize_session: chooses the strategy to update the
         attributes on objects in the session.   See the section
         :ref:`orm_expression_update_delete` for a discussion of these
         strategies.

        :param update_args: Optional dictionary, if present will be passed
         to the underlying :func:`_expression.update`
         construct as the ``**kw`` for
         the object.  May be used to pass dialect-specific arguments such
         as ``mysql_limit``, as well as other special arguments such as
         :paramref:`~sqlalchemy.sql.expression.update.preserve_parameter_order`.

        :return: the count of rows matched as returned by the database's
         "row count" feature.


        .. seealso::

            :ref:`orm_expression_update_delete`


        """

        update_args = update_args or {}

        bulk_ud = BulkUpdate(self, values, update_args)

        if self.dispatch.before_compile_update:
            for fn in self.dispatch.before_compile_update:
                new_query = fn(bulk_ud.query, bulk_ud)
                if new_query is not None:
                    bulk_ud.query = new_query
            self = bulk_ud.query

        upd = sql.update(*self._raw_columns)

        ppo = update_args.pop("preserve_parameter_order", False)
        if ppo:
            upd = upd.ordered_values(*values)
        else:
            upd = upd.values(values)
        if update_args:
            upd = upd.with_dialect_options(**update_args)

        upd._where_criteria = self._where_criteria
        result = self.session.execute(
            upd,
            self._params,
            execution_options={"synchronize_session": synchronize_session},
        )
        bulk_ud.result = result
        self.session.dispatch.after_bulk_update(bulk_ud)
        result.close()
        return result.rowcount

    def _compile_state(self, for_statement=False, **kw):
        """Create an out-of-compiler ORMCompileState object.

        The ORMCompileState object is normally created directly as a result
        of the SQLCompiler.process() method being handed a Select()
        or FromStatement() object that uses the "orm" plugin.   This method
        provides a means of creating this ORMCompileState object directly
        without using the compiler.

        This method is used only for deprecated cases, which include
        the .from_self() method for a Query that has multiple levels
        of .from_self() in use, as well as the instances() method.  It is
        also used within the test suite to generate ORMCompileState objects
        for test purposes.

        """

        stmt = self._statement_20(for_statement=for_statement, **kw)
        assert for_statement == stmt._compile_options._for_statement

        # this chooses between ORMFromStatementCompileState and
        # ORMSelectCompileState.  We could also base this on
        # query._statement is not None as we have the ORM Query here
        # however this is the more general path.
        compile_state_cls = ORMCompileState._get_plugin_class_for_plugin(
            stmt, "orm"
        )

        return compile_state_cls.create_for_statement(stmt, None)

    def _compile_context(self, for_statement=False):
        compile_state = self._compile_state(for_statement=for_statement)
        context = QueryContext(
            compile_state,
            compile_state.statement,
            self._params,
            self.session,
            self.load_options,
        )

        return context


class FromStatement(GroupedElement, SelectBase, Executable):
    """Core construct that represents a load of ORM objects from a finished
    select or text construct.

    """

    __visit_name__ = "orm_from_statement"

    _compile_options = ORMFromStatementCompileState.default_compile_options

    _compile_state_factory = ORMFromStatementCompileState.create_for_statement

    _is_future = True

    _for_update_arg = None

    _traverse_internals = [
        ("_raw_columns", InternalTraversal.dp_clauseelement_list),
        ("element", InternalTraversal.dp_clauseelement),
    ] + Executable._executable_traverse_internals

    _cache_key_traversal = _traverse_internals + [
        ("_compile_options", InternalTraversal.dp_has_cache_key)
    ]

    def __init__(self, entities, element):
        self._raw_columns = [
            coercions.expect(
                roles.ColumnsClauseRole, ent, apply_propagate_attrs=self
            )
            for ent in util.to_list(entities)
        ]
        self.element = element

    def get_label_style(self):
        return self._label_style

    def set_label_style(self, label_style):
        return SelectStatementGrouping(
            self.element.set_label_style(label_style)
        )

    @property
    def _label_style(self):
        return self.element._label_style

    def _compiler_dispatch(self, compiler, **kw):

        """provide a fixed _compiler_dispatch method.

        This is roughly similar to using the sqlalchemy.ext.compiler
        ``@compiles`` extension.

        """

        compile_state = self._compile_state_factory(self, compiler, **kw)

        toplevel = not compiler.stack

        if toplevel:
            compiler.compile_state = compile_state

        return compiler.process(compile_state.statement, **kw)

    def _ensure_disambiguated_names(self):
        return self

    def get_children(self, **kw):
        for elem in itertools.chain.from_iterable(
            element._from_objects for element in self._raw_columns
        ):
            yield elem
        for elem in super(FromStatement, self).get_children(**kw):
            yield elem

    @property
    def _returning(self):
        return self.element._returning if self.element.is_dml else None

    @property
    def _inline(self):
        return self.element._inline if self.element.is_dml else None


class AliasOption(interfaces.LoaderOption):
    @util.deprecated(
        "1.4",
        "The :class:`.AliasOption` is not necessary "
        "for entities to be matched up to a query that is established "
        "via :meth:`.Query.from_statement` and now does nothing.",
    )
    def __init__(self, alias):
        r"""Return a :class:`.MapperOption` that will indicate to the
        :class:`_query.Query`
        that the main table has been aliased.

        """

    def process_compile_state(self, compile_state):
        pass


class BulkUD(object):
    """State used for the orm.Query version of update() / delete().

    This object is now specific to Query only.

    """

    def __init__(self, query):
        self.query = query.enable_eagerloads(False)
        self._validate_query_state()
        self.mapper = self.query._entity_from_pre_ent_zero()

    def _validate_query_state(self):
        for attr, methname, notset, op in (
            ("_limit_clause", "limit()", None, operator.is_),
            ("_offset_clause", "offset()", None, operator.is_),
            ("_order_by_clauses", "order_by()", (), operator.eq),
            ("_group_by_clauses", "group_by()", (), operator.eq),
            ("_distinct", "distinct()", False, operator.is_),
            (
                "_from_obj",
                "join(), outerjoin(), select_from(), or from_self()",
                (),
                operator.eq,
            ),
            (
                "_legacy_setup_joins",
                "join(), outerjoin(), select_from(), or from_self()",
                (),
                operator.eq,
            ),
        ):
            if not op(getattr(self.query, attr), notset):
                raise sa_exc.InvalidRequestError(
                    "Can't call Query.update() or Query.delete() "
                    "when %s has been called" % (methname,)
                )

    @property
    def session(self):
        return self.query.session


class BulkUpdate(BulkUD):
    """BulkUD which handles UPDATEs."""

    def __init__(self, query, values, update_kwargs):
        super(BulkUpdate, self).__init__(query)
        self.values = values
        self.update_kwargs = update_kwargs


class BulkDelete(BulkUD):
    """BulkUD which handles DELETEs."""
