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Qichao
2023-10-08 20:59:00 +08:00
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# ext/asyncio/result.py
# Copyright (C) 2020-2022 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: https://www.opensource.org/licenses/mit-license.php
import operator
from . import exc as async_exc
from ...engine.result import _NO_ROW
from ...engine.result import FilterResult
from ...engine.result import FrozenResult
from ...engine.result import MergedResult
from ...sql.base import _generative
from ...util.concurrency import greenlet_spawn
class AsyncCommon(FilterResult):
async def close(self):
"""Close this result."""
await greenlet_spawn(self._real_result.close)
class AsyncResult(AsyncCommon):
"""An asyncio wrapper around a :class:`_result.Result` object.
The :class:`_asyncio.AsyncResult` only applies to statement executions that
use a server-side cursor. It is returned only from the
:meth:`_asyncio.AsyncConnection.stream` and
:meth:`_asyncio.AsyncSession.stream` methods.
.. note:: As is the case with :class:`_engine.Result`, this object is
used for ORM results returned by :meth:`_asyncio.AsyncSession.execute`,
which can yield instances of ORM mapped objects either individually or
within tuple-like rows. Note that these result objects do not
deduplicate instances or rows automatically as is the case with the
legacy :class:`_orm.Query` object. For in-Python de-duplication of
instances or rows, use the :meth:`_asyncio.AsyncResult.unique` modifier
method.
.. versionadded:: 1.4
"""
def __init__(self, real_result):
self._real_result = real_result
self._metadata = real_result._metadata
self._unique_filter_state = real_result._unique_filter_state
# BaseCursorResult pre-generates the "_row_getter". Use that
# if available rather than building a second one
if "_row_getter" in real_result.__dict__:
self._set_memoized_attribute(
"_row_getter", real_result.__dict__["_row_getter"]
)
def keys(self):
"""Return the :meth:`_engine.Result.keys` collection from the
underlying :class:`_engine.Result`.
"""
return self._metadata.keys
@_generative
def unique(self, strategy=None):
"""Apply unique filtering to the objects returned by this
:class:`_asyncio.AsyncResult`.
Refer to :meth:`_engine.Result.unique` in the synchronous
SQLAlchemy API for a complete behavioral description.
"""
self._unique_filter_state = (set(), strategy)
def columns(self, *col_expressions):
r"""Establish the columns that should be returned in each row.
Refer to :meth:`_engine.Result.columns` in the synchronous
SQLAlchemy API for a complete behavioral description.
"""
return self._column_slices(col_expressions)
async def partitions(self, size=None):
"""Iterate through sub-lists of rows of the size given.
An async iterator is returned::
async def scroll_results(connection):
result = await connection.stream(select(users_table))
async for partition in result.partitions(100):
print("list of rows: %s" % partition)
.. seealso::
:meth:`_engine.Result.partitions`
"""
getter = self._manyrow_getter
while True:
partition = await greenlet_spawn(getter, self, size)
if partition:
yield partition
else:
break
async def fetchone(self):
"""Fetch one row.
When all rows are exhausted, returns None.
This method is provided for backwards compatibility with
SQLAlchemy 1.x.x.
To fetch the first row of a result only, use the
:meth:`_engine.Result.first` method. To iterate through all
rows, iterate the :class:`_engine.Result` object directly.
:return: a :class:`.Row` object if no filters are applied, or None
if no rows remain.
"""
row = await greenlet_spawn(self._onerow_getter, self)
if row is _NO_ROW:
return None
else:
return row
async def fetchmany(self, size=None):
"""Fetch many rows.
When all rows are exhausted, returns an empty list.
This method is provided for backwards compatibility with
SQLAlchemy 1.x.x.
To fetch rows in groups, use the
:meth:`._asyncio.AsyncResult.partitions` method.
:return: a list of :class:`.Row` objects.
.. seealso::
:meth:`_asyncio.AsyncResult.partitions`
"""
return await greenlet_spawn(self._manyrow_getter, self, size)
async def all(self):
"""Return all rows in a list.
Closes the result set after invocation. Subsequent invocations
will return an empty list.
:return: a list of :class:`.Row` objects.
"""
return await greenlet_spawn(self._allrows)
def __aiter__(self):
return self
async def __anext__(self):
row = await greenlet_spawn(self._onerow_getter, self)
if row is _NO_ROW:
raise StopAsyncIteration()
else:
return row
async def first(self):
"""Fetch the first row or None if no row is present.
Closes the result set and discards remaining rows.
.. note:: This method returns one **row**, e.g. tuple, by default. To
return exactly one single scalar value, that is, the first column of
the first row, use the :meth:`_asyncio.AsyncResult.scalar` method,
or combine :meth:`_asyncio.AsyncResult.scalars` and
:meth:`_asyncio.AsyncResult.first`.
:return: a :class:`.Row` object, or None
if no rows remain.
.. seealso::
:meth:`_asyncio.AsyncResult.scalar`
:meth:`_asyncio.AsyncResult.one`
"""
return await greenlet_spawn(self._only_one_row, False, False, False)
async def one_or_none(self):
"""Return at most one result or raise an exception.
Returns ``None`` if the result has no rows.
Raises :class:`.MultipleResultsFound`
if multiple rows are returned.
.. versionadded:: 1.4
:return: The first :class:`.Row` or None if no row is available.
:raises: :class:`.MultipleResultsFound`
.. seealso::
:meth:`_asyncio.AsyncResult.first`
:meth:`_asyncio.AsyncResult.one`
"""
return await greenlet_spawn(self._only_one_row, True, False, False)
async def scalar_one(self):
"""Return exactly one scalar result or raise an exception.
This is equivalent to calling :meth:`_asyncio.AsyncResult.scalars` and
then :meth:`_asyncio.AsyncResult.one`.
.. seealso::
:meth:`_asyncio.AsyncResult.one`
:meth:`_asyncio.AsyncResult.scalars`
"""
return await greenlet_spawn(self._only_one_row, True, True, True)
async def scalar_one_or_none(self):
"""Return exactly one or no scalar result.
This is equivalent to calling :meth:`_asyncio.AsyncResult.scalars` and
then :meth:`_asyncio.AsyncResult.one_or_none`.
.. seealso::
:meth:`_asyncio.AsyncResult.one_or_none`
:meth:`_asyncio.AsyncResult.scalars`
"""
return await greenlet_spawn(self._only_one_row, True, False, True)
async def one(self):
"""Return exactly one row or raise an exception.
Raises :class:`.NoResultFound` if the result returns no
rows, or :class:`.MultipleResultsFound` if multiple rows
would be returned.
.. note:: This method returns one **row**, e.g. tuple, by default.
To return exactly one single scalar value, that is, the first
column of the first row, use the
:meth:`_asyncio.AsyncResult.scalar_one` method, or combine
:meth:`_asyncio.AsyncResult.scalars` and
:meth:`_asyncio.AsyncResult.one`.
.. versionadded:: 1.4
:return: The first :class:`.Row`.
:raises: :class:`.MultipleResultsFound`, :class:`.NoResultFound`
.. seealso::
:meth:`_asyncio.AsyncResult.first`
:meth:`_asyncio.AsyncResult.one_or_none`
:meth:`_asyncio.AsyncResult.scalar_one`
"""
return await greenlet_spawn(self._only_one_row, True, True, False)
async def scalar(self):
"""Fetch the first column of the first row, and close the result set.
Returns None if there are no rows to fetch.
No validation is performed to test if additional rows remain.
After calling this method, the object is fully closed,
e.g. the :meth:`_engine.CursorResult.close`
method will have been called.
:return: a Python scalar value , or None if no rows remain.
"""
return await greenlet_spawn(self._only_one_row, False, False, True)
async def freeze(self):
"""Return a callable object that will produce copies of this
:class:`_asyncio.AsyncResult` when invoked.
The callable object returned is an instance of
:class:`_engine.FrozenResult`.
This is used for result set caching. The method must be called
on the result when it has been unconsumed, and calling the method
will consume the result fully. When the :class:`_engine.FrozenResult`
is retrieved from a cache, it can be called any number of times where
it will produce a new :class:`_engine.Result` object each time
against its stored set of rows.
.. seealso::
:ref:`do_orm_execute_re_executing` - example usage within the
ORM to implement a result-set cache.
"""
return await greenlet_spawn(FrozenResult, self)
def merge(self, *others):
"""Merge this :class:`_asyncio.AsyncResult` with other compatible
result objects.
The object returned is an instance of :class:`_engine.MergedResult`,
which will be composed of iterators from the given result
objects.
The new result will use the metadata from this result object.
The subsequent result objects must be against an identical
set of result / cursor metadata, otherwise the behavior is
undefined.
"""
return MergedResult(self._metadata, (self,) + others)
def scalars(self, index=0):
"""Return an :class:`_asyncio.AsyncScalarResult` filtering object which
will return single elements rather than :class:`_row.Row` objects.
Refer to :meth:`_result.Result.scalars` in the synchronous
SQLAlchemy API for a complete behavioral description.
:param index: integer or row key indicating the column to be fetched
from each row, defaults to ``0`` indicating the first column.
:return: a new :class:`_asyncio.AsyncScalarResult` filtering object
referring to this :class:`_asyncio.AsyncResult` object.
"""
return AsyncScalarResult(self._real_result, index)
def mappings(self):
"""Apply a mappings filter to returned rows, returning an instance of
:class:`_asyncio.AsyncMappingResult`.
When this filter is applied, fetching rows will return
:class:`.RowMapping` objects instead of :class:`.Row` objects.
Refer to :meth:`_result.Result.mappings` in the synchronous
SQLAlchemy API for a complete behavioral description.
:return: a new :class:`_asyncio.AsyncMappingResult` filtering object
referring to the underlying :class:`_result.Result` object.
"""
return AsyncMappingResult(self._real_result)
class AsyncScalarResult(AsyncCommon):
"""A wrapper for a :class:`_asyncio.AsyncResult` that returns scalar values
rather than :class:`_row.Row` values.
The :class:`_asyncio.AsyncScalarResult` object is acquired by calling the
:meth:`_asyncio.AsyncResult.scalars` method.
Refer to the :class:`_result.ScalarResult` object in the synchronous
SQLAlchemy API for a complete behavioral description.
.. versionadded:: 1.4
"""
_generate_rows = False
def __init__(self, real_result, index):
self._real_result = real_result
if real_result._source_supports_scalars:
self._metadata = real_result._metadata
self._post_creational_filter = None
else:
self._metadata = real_result._metadata._reduce([index])
self._post_creational_filter = operator.itemgetter(0)
self._unique_filter_state = real_result._unique_filter_state
def unique(self, strategy=None):
"""Apply unique filtering to the objects returned by this
:class:`_asyncio.AsyncScalarResult`.
See :meth:`_asyncio.AsyncResult.unique` for usage details.
"""
self._unique_filter_state = (set(), strategy)
return self
async def partitions(self, size=None):
"""Iterate through sub-lists of elements of the size given.
Equivalent to :meth:`_asyncio.AsyncResult.partitions` except that
scalar values, rather than :class:`_result.Row` objects,
are returned.
"""
getter = self._manyrow_getter
while True:
partition = await greenlet_spawn(getter, self, size)
if partition:
yield partition
else:
break
async def fetchall(self):
"""A synonym for the :meth:`_asyncio.AsyncScalarResult.all` method."""
return await greenlet_spawn(self._allrows)
async def fetchmany(self, size=None):
"""Fetch many objects.
Equivalent to :meth:`_asyncio.AsyncResult.fetchmany` except that
scalar values, rather than :class:`_result.Row` objects,
are returned.
"""
return await greenlet_spawn(self._manyrow_getter, self, size)
async def all(self):
"""Return all scalar values in a list.
Equivalent to :meth:`_asyncio.AsyncResult.all` except that
scalar values, rather than :class:`_result.Row` objects,
are returned.
"""
return await greenlet_spawn(self._allrows)
def __aiter__(self):
return self
async def __anext__(self):
row = await greenlet_spawn(self._onerow_getter, self)
if row is _NO_ROW:
raise StopAsyncIteration()
else:
return row
async def first(self):
"""Fetch the first object or None if no object is present.
Equivalent to :meth:`_asyncio.AsyncResult.first` except that
scalar values, rather than :class:`_result.Row` objects,
are returned.
"""
return await greenlet_spawn(self._only_one_row, False, False, False)
async def one_or_none(self):
"""Return at most one object or raise an exception.
Equivalent to :meth:`_asyncio.AsyncResult.one_or_none` except that
scalar values, rather than :class:`_result.Row` objects,
are returned.
"""
return await greenlet_spawn(self._only_one_row, True, False, False)
async def one(self):
"""Return exactly one object or raise an exception.
Equivalent to :meth:`_asyncio.AsyncResult.one` except that
scalar values, rather than :class:`_result.Row` objects,
are returned.
"""
return await greenlet_spawn(self._only_one_row, True, True, False)
class AsyncMappingResult(AsyncCommon):
"""A wrapper for a :class:`_asyncio.AsyncResult` that returns dictionary
values rather than :class:`_engine.Row` values.
The :class:`_asyncio.AsyncMappingResult` object is acquired by calling the
:meth:`_asyncio.AsyncResult.mappings` method.
Refer to the :class:`_result.MappingResult` object in the synchronous
SQLAlchemy API for a complete behavioral description.
.. versionadded:: 1.4
"""
_generate_rows = True
_post_creational_filter = operator.attrgetter("_mapping")
def __init__(self, result):
self._real_result = result
self._unique_filter_state = result._unique_filter_state
self._metadata = result._metadata
if result._source_supports_scalars:
self._metadata = self._metadata._reduce([0])
def keys(self):
"""Return an iterable view which yields the string keys that would
be represented by each :class:`.Row`.
The view also can be tested for key containment using the Python
``in`` operator, which will test both for the string keys represented
in the view, as well as for alternate keys such as column objects.
.. versionchanged:: 1.4 a key view object is returned rather than a
plain list.
"""
return self._metadata.keys
def unique(self, strategy=None):
"""Apply unique filtering to the objects returned by this
:class:`_asyncio.AsyncMappingResult`.
See :meth:`_asyncio.AsyncResult.unique` for usage details.
"""
self._unique_filter_state = (set(), strategy)
return self
def columns(self, *col_expressions):
r"""Establish the columns that should be returned in each row."""
return self._column_slices(col_expressions)
async def partitions(self, size=None):
"""Iterate through sub-lists of elements of the size given.
Equivalent to :meth:`_asyncio.AsyncResult.partitions` except that
mapping values, rather than :class:`_result.Row` objects,
are returned.
"""
getter = self._manyrow_getter
while True:
partition = await greenlet_spawn(getter, self, size)
if partition:
yield partition
else:
break
async def fetchall(self):
"""A synonym for the :meth:`_asyncio.AsyncMappingResult.all` method."""
return await greenlet_spawn(self._allrows)
async def fetchone(self):
"""Fetch one object.
Equivalent to :meth:`_asyncio.AsyncResult.fetchone` except that
mapping values, rather than :class:`_result.Row` objects,
are returned.
"""
row = await greenlet_spawn(self._onerow_getter, self)
if row is _NO_ROW:
return None
else:
return row
async def fetchmany(self, size=None):
"""Fetch many objects.
Equivalent to :meth:`_asyncio.AsyncResult.fetchmany` except that
mapping values, rather than :class:`_result.Row` objects,
are returned.
"""
return await greenlet_spawn(self._manyrow_getter, self, size)
async def all(self):
"""Return all scalar values in a list.
Equivalent to :meth:`_asyncio.AsyncResult.all` except that
mapping values, rather than :class:`_result.Row` objects,
are returned.
"""
return await greenlet_spawn(self._allrows)
def __aiter__(self):
return self
async def __anext__(self):
row = await greenlet_spawn(self._onerow_getter, self)
if row is _NO_ROW:
raise StopAsyncIteration()
else:
return row
async def first(self):
"""Fetch the first object or None if no object is present.
Equivalent to :meth:`_asyncio.AsyncResult.first` except that
mapping values, rather than :class:`_result.Row` objects,
are returned.
"""
return await greenlet_spawn(self._only_one_row, False, False, False)
async def one_or_none(self):
"""Return at most one object or raise an exception.
Equivalent to :meth:`_asyncio.AsyncResult.one_or_none` except that
mapping values, rather than :class:`_result.Row` objects,
are returned.
"""
return await greenlet_spawn(self._only_one_row, True, False, False)
async def one(self):
"""Return exactly one object or raise an exception.
Equivalent to :meth:`_asyncio.AsyncResult.one` except that
mapping values, rather than :class:`_result.Row` objects,
are returned.
"""
return await greenlet_spawn(self._only_one_row, True, True, False)
async def _ensure_sync_result(result, calling_method):
if not result._is_cursor:
cursor_result = getattr(result, "raw", None)
else:
cursor_result = result
if cursor_result and cursor_result.context._is_server_side:
await greenlet_spawn(cursor_result.close)
raise async_exc.AsyncMethodRequired(
"Can't use the %s.%s() method with a "
"server-side cursor. "
"Use the %s.stream() method for an async "
"streaming result set."
% (
calling_method.__self__.__class__.__name__,
calling_method.__name__,
calling_method.__self__.__class__.__name__,
)
)
return result