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from ..sql import coercions
from ..sql import roles
from ..sql.base import _generative
from ..sql.selectable import GenerativeSelect
from ..sql.selectable import Select as _LegacySelect
from ..sql.selectable import SelectState
from ..sql.util import _entity_namespace_key
class Select(_LegacySelect):
_is_future = True
_setup_joins = ()
_legacy_setup_joins = ()
inherit_cache = True
@classmethod
def _create_select(cls, *entities):
raise NotImplementedError("use _create_future_select")
@classmethod
def _create_future_select(cls, *entities):
r"""Construct a new :class:`_expression.Select` using the 2.
x style API.
.. versionadded:: 2.0 - the :func:`_future.select` construct is
the same construct as the one returned by
:func:`_expression.select`, except that the function only
accepts the "columns clause" entities up front; the rest of the
state of the SELECT should be built up using generative methods.
Similar functionality is also available via the
:meth:`_expression.FromClause.select` method on any
:class:`_expression.FromClause`.
.. seealso::
:ref:`coretutorial_selecting` - Core Tutorial description of
:func:`_expression.select`.
:param \*entities:
Entities to SELECT from. For Core usage, this is typically a series
of :class:`_expression.ColumnElement` and / or
:class:`_expression.FromClause`
objects which will form the columns clause of the resulting
statement. For those objects that are instances of
:class:`_expression.FromClause` (typically :class:`_schema.Table`
or :class:`_expression.Alias`
objects), the :attr:`_expression.FromClause.c`
collection is extracted
to form a collection of :class:`_expression.ColumnElement` objects.
This parameter will also accept :class:`_expression.TextClause`
constructs as
given, as well as ORM-mapped classes.
"""
self = cls.__new__(cls)
self._raw_columns = [
coercions.expect(
roles.ColumnsClauseRole, ent, apply_propagate_attrs=self
)
for ent in entities
]
GenerativeSelect.__init__(self)
return self
def filter(self, *criteria):
"""A synonym for the :meth:`_future.Select.where` method."""
return self.where(*criteria)
def _exported_columns_iterator(self):
meth = SelectState.get_plugin_class(self).exported_columns_iterator
return meth(self)
def _filter_by_zero(self):
if self._setup_joins:
meth = SelectState.get_plugin_class(
self
).determine_last_joined_entity
_last_joined_entity = meth(self)
if _last_joined_entity is not None:
return _last_joined_entity
if self._from_obj:
return self._from_obj[0]
return self._raw_columns[0]
def filter_by(self, **kwargs):
r"""Apply the given filtering criterion as a WHERE clause
to this select.
"""
from_entity = self._filter_by_zero()
clauses = [
_entity_namespace_key(from_entity, key) == value
for key, value in kwargs.items()
]
return self.filter(*clauses)
@property
def column_descriptions(self):
"""Return a 'column descriptions' structure which may be
plugin-specific.
"""
meth = SelectState.get_plugin_class(self).get_column_descriptions
return meth(self)
@_generative
def join(self, target, onclause=None, isouter=False, full=False):
r"""Create a SQL JOIN against this :class:`_expression.Select`
object's criterion
and apply generatively, returning the newly resulting
:class:`_expression.Select`.
"""
target = coercions.expect(
roles.JoinTargetRole, target, apply_propagate_attrs=self
)
self._setup_joins += (
(target, onclause, None, {"isouter": isouter, "full": full}),
)
@_generative
def join_from(
self, from_, target, onclause=None, isouter=False, full=False
):
r"""Create a SQL JOIN against this :class:`_expression.Select`
object's criterion
and apply generatively, returning the newly resulting
:class:`_expression.Select`.
"""
# note the order of parsing from vs. target is important here, as we
# are also deriving the source of the plugin (i.e. the subject mapper
# in an ORM query) which should favor the "from_" over the "target"
from_ = coercions.expect(
roles.FromClauseRole, from_, apply_propagate_attrs=self
)
target = coercions.expect(
roles.JoinTargetRole, target, apply_propagate_attrs=self
)
self._setup_joins += (
(target, onclause, from_, {"isouter": isouter, "full": full}),
)
def outerjoin(self, target, onclause=None, full=False):
"""Create a left outer join.
"""
return self.join(target, onclause=onclause, isouter=True, full=full,)
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