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575 lines
17 KiB
575 lines
17 KiB
# ext/baked.py
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# Copyright (C) 2005-2024 the SQLAlchemy authors and contributors
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# <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: https://www.opensource.org/licenses/mit-license.php
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# mypy: ignore-errors
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"""Baked query extension.
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Provides a creational pattern for the :class:`.query.Query` object which
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allows the fully constructed object, Core select statement, and string
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compiled result to be fully cached.
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"""
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import collections.abc as collections_abc
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import logging
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from .. import exc as sa_exc
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from .. import util
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from ..orm import exc as orm_exc
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from ..orm.query import Query
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from ..orm.session import Session
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from ..sql import func
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from ..sql import literal_column
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from ..sql import util as sql_util
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log = logging.getLogger(__name__)
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class Bakery:
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"""Callable which returns a :class:`.BakedQuery`.
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This object is returned by the class method
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:meth:`.BakedQuery.bakery`. It exists as an object
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so that the "cache" can be easily inspected.
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.. versionadded:: 1.2
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"""
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__slots__ = "cls", "cache"
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def __init__(self, cls_, cache):
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self.cls = cls_
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self.cache = cache
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def __call__(self, initial_fn, *args):
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return self.cls(self.cache, initial_fn, args)
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class BakedQuery:
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"""A builder object for :class:`.query.Query` objects."""
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__slots__ = "steps", "_bakery", "_cache_key", "_spoiled"
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def __init__(self, bakery, initial_fn, args=()):
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self._cache_key = ()
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self._update_cache_key(initial_fn, args)
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self.steps = [initial_fn]
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self._spoiled = False
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self._bakery = bakery
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@classmethod
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def bakery(cls, size=200, _size_alert=None):
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"""Construct a new bakery.
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:return: an instance of :class:`.Bakery`
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"""
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return Bakery(cls, util.LRUCache(size, size_alert=_size_alert))
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def _clone(self):
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b1 = BakedQuery.__new__(BakedQuery)
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b1._cache_key = self._cache_key
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b1.steps = list(self.steps)
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b1._bakery = self._bakery
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b1._spoiled = self._spoiled
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return b1
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def _update_cache_key(self, fn, args=()):
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self._cache_key += (fn.__code__,) + args
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def __iadd__(self, other):
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if isinstance(other, tuple):
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self.add_criteria(*other)
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else:
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self.add_criteria(other)
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return self
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def __add__(self, other):
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if isinstance(other, tuple):
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return self.with_criteria(*other)
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else:
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return self.with_criteria(other)
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def add_criteria(self, fn, *args):
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"""Add a criteria function to this :class:`.BakedQuery`.
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This is equivalent to using the ``+=`` operator to
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modify a :class:`.BakedQuery` in-place.
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"""
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self._update_cache_key(fn, args)
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self.steps.append(fn)
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return self
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def with_criteria(self, fn, *args):
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"""Add a criteria function to a :class:`.BakedQuery` cloned from this
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one.
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This is equivalent to using the ``+`` operator to
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produce a new :class:`.BakedQuery` with modifications.
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"""
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return self._clone().add_criteria(fn, *args)
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def for_session(self, session):
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"""Return a :class:`_baked.Result` object for this
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:class:`.BakedQuery`.
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This is equivalent to calling the :class:`.BakedQuery` as a
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Python callable, e.g. ``result = my_baked_query(session)``.
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"""
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return Result(self, session)
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def __call__(self, session):
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return self.for_session(session)
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def spoil(self, full=False):
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"""Cancel any query caching that will occur on this BakedQuery object.
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The BakedQuery can continue to be used normally, however additional
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creational functions will not be cached; they will be called
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on every invocation.
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This is to support the case where a particular step in constructing
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a baked query disqualifies the query from being cacheable, such
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as a variant that relies upon some uncacheable value.
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:param full: if False, only functions added to this
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:class:`.BakedQuery` object subsequent to the spoil step will be
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non-cached; the state of the :class:`.BakedQuery` up until
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this point will be pulled from the cache. If True, then the
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entire :class:`_query.Query` object is built from scratch each
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time, with all creational functions being called on each
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invocation.
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"""
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if not full and not self._spoiled:
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_spoil_point = self._clone()
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_spoil_point._cache_key += ("_query_only",)
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self.steps = [_spoil_point._retrieve_baked_query]
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self._spoiled = True
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return self
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def _effective_key(self, session):
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"""Return the key that actually goes into the cache dictionary for
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this :class:`.BakedQuery`, taking into account the given
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:class:`.Session`.
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This basically means we also will include the session's query_class,
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as the actual :class:`_query.Query` object is part of what's cached
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and needs to match the type of :class:`_query.Query` that a later
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session will want to use.
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"""
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return self._cache_key + (session._query_cls,)
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def _with_lazyload_options(self, options, effective_path, cache_path=None):
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"""Cloning version of _add_lazyload_options."""
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q = self._clone()
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q._add_lazyload_options(options, effective_path, cache_path=cache_path)
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return q
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def _add_lazyload_options(self, options, effective_path, cache_path=None):
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"""Used by per-state lazy loaders to add options to the
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"lazy load" query from a parent query.
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Creates a cache key based on given load path and query options;
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if a repeatable cache key cannot be generated, the query is
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"spoiled" so that it won't use caching.
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"""
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key = ()
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if not cache_path:
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cache_path = effective_path
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for opt in options:
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if opt._is_legacy_option or opt._is_compile_state:
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ck = opt._generate_cache_key()
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if ck is None:
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self.spoil(full=True)
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else:
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assert not ck[1], (
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"loader options with variable bound parameters "
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"not supported with baked queries. Please "
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"use new-style select() statements for cached "
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"ORM queries."
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)
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key += ck[0]
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self.add_criteria(
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lambda q: q._with_current_path(effective_path).options(*options),
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cache_path.path,
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key,
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)
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def _retrieve_baked_query(self, session):
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query = self._bakery.get(self._effective_key(session), None)
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if query is None:
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query = self._as_query(session)
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self._bakery[self._effective_key(session)] = query.with_session(
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None
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)
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return query.with_session(session)
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def _bake(self, session):
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query = self._as_query(session)
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query.session = None
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# in 1.4, this is where before_compile() event is
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# invoked
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statement = query._statement_20()
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# if the query is not safe to cache, we still do everything as though
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# we did cache it, since the receiver of _bake() assumes subqueryload
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# context was set up, etc.
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#
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# note also we want to cache the statement itself because this
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# allows the statement itself to hold onto its cache key that is
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# used by the Connection, which in itself is more expensive to
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# generate than what BakedQuery was able to provide in 1.3 and prior
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if statement._compile_options._bake_ok:
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self._bakery[self._effective_key(session)] = (
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query,
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statement,
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)
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return query, statement
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def to_query(self, query_or_session):
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"""Return the :class:`_query.Query` object for use as a subquery.
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This method should be used within the lambda callable being used
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to generate a step of an enclosing :class:`.BakedQuery`. The
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parameter should normally be the :class:`_query.Query` object that
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is passed to the lambda::
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sub_bq = self.bakery(lambda s: s.query(User.name))
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sub_bq += lambda q: q.filter(
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User.id == Address.user_id).correlate(Address)
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main_bq = self.bakery(lambda s: s.query(Address))
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main_bq += lambda q: q.filter(
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sub_bq.to_query(q).exists())
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In the case where the subquery is used in the first callable against
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a :class:`.Session`, the :class:`.Session` is also accepted::
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sub_bq = self.bakery(lambda s: s.query(User.name))
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sub_bq += lambda q: q.filter(
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User.id == Address.user_id).correlate(Address)
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main_bq = self.bakery(
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lambda s: s.query(
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Address.id, sub_bq.to_query(q).scalar_subquery())
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)
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:param query_or_session: a :class:`_query.Query` object or a class
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:class:`.Session` object, that is assumed to be within the context
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of an enclosing :class:`.BakedQuery` callable.
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.. versionadded:: 1.3
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"""
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if isinstance(query_or_session, Session):
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session = query_or_session
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elif isinstance(query_or_session, Query):
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session = query_or_session.session
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if session is None:
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raise sa_exc.ArgumentError(
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"Given Query needs to be associated with a Session"
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)
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else:
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raise TypeError(
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"Query or Session object expected, got %r."
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% type(query_or_session)
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)
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return self._as_query(session)
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def _as_query(self, session):
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query = self.steps[0](session)
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for step in self.steps[1:]:
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query = step(query)
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return query
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class Result:
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"""Invokes a :class:`.BakedQuery` against a :class:`.Session`.
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The :class:`_baked.Result` object is where the actual :class:`.query.Query`
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object gets created, or retrieved from the cache,
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against a target :class:`.Session`, and is then invoked for results.
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"""
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__slots__ = "bq", "session", "_params", "_post_criteria"
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def __init__(self, bq, session):
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self.bq = bq
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self.session = session
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self._params = {}
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self._post_criteria = []
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def params(self, *args, **kw):
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"""Specify parameters to be replaced into the string SQL statement."""
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if len(args) == 1:
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kw.update(args[0])
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elif len(args) > 0:
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raise sa_exc.ArgumentError(
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"params() takes zero or one positional argument, "
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"which is a dictionary."
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)
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self._params.update(kw)
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return self
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def _using_post_criteria(self, fns):
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if fns:
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self._post_criteria.extend(fns)
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return self
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def with_post_criteria(self, fn):
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"""Add a criteria function that will be applied post-cache.
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This adds a function that will be run against the
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:class:`_query.Query` object after it is retrieved from the
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cache. This currently includes **only** the
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:meth:`_query.Query.params` and :meth:`_query.Query.execution_options`
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methods.
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.. warning:: :meth:`_baked.Result.with_post_criteria`
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functions are applied
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to the :class:`_query.Query`
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object **after** the query's SQL statement
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object has been retrieved from the cache. Only
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:meth:`_query.Query.params` and
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:meth:`_query.Query.execution_options`
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methods should be used.
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.. versionadded:: 1.2
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"""
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return self._using_post_criteria([fn])
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def _as_query(self):
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q = self.bq._as_query(self.session).params(self._params)
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for fn in self._post_criteria:
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q = fn(q)
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return q
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def __str__(self):
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return str(self._as_query())
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def __iter__(self):
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return self._iter().__iter__()
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def _iter(self):
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bq = self.bq
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if not self.session.enable_baked_queries or bq._spoiled:
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return self._as_query()._iter()
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query, statement = bq._bakery.get(
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bq._effective_key(self.session), (None, None)
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)
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if query is None:
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query, statement = bq._bake(self.session)
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if self._params:
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q = query.params(self._params)
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else:
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q = query
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for fn in self._post_criteria:
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q = fn(q)
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params = q._params
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execution_options = dict(q._execution_options)
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execution_options.update(
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{
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"_sa_orm_load_options": q.load_options,
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"compiled_cache": bq._bakery,
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}
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)
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result = self.session.execute(
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statement, params, execution_options=execution_options
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)
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if result._attributes.get("is_single_entity", False):
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result = result.scalars()
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if result._attributes.get("filtered", False):
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result = result.unique()
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return result
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def count(self):
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"""return the 'count'.
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Equivalent to :meth:`_query.Query.count`.
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Note this uses a subquery to ensure an accurate count regardless
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of the structure of the original statement.
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"""
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col = func.count(literal_column("*"))
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bq = self.bq.with_criteria(lambda q: q._legacy_from_self(col))
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return bq.for_session(self.session).params(self._params).scalar()
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def scalar(self):
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"""Return the first element of the first result or None
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if no rows present. If multiple rows are returned,
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raises MultipleResultsFound.
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Equivalent to :meth:`_query.Query.scalar`.
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"""
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try:
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ret = self.one()
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if not isinstance(ret, collections_abc.Sequence):
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return ret
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return ret[0]
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except orm_exc.NoResultFound:
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return None
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def first(self):
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"""Return the first row.
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Equivalent to :meth:`_query.Query.first`.
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"""
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bq = self.bq.with_criteria(lambda q: q.slice(0, 1))
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return (
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bq.for_session(self.session)
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.params(self._params)
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._using_post_criteria(self._post_criteria)
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._iter()
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.first()
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)
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def one(self):
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"""Return exactly one result or raise an exception.
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Equivalent to :meth:`_query.Query.one`.
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"""
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return self._iter().one()
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def one_or_none(self):
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"""Return one or zero results, or raise an exception for multiple
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rows.
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Equivalent to :meth:`_query.Query.one_or_none`.
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"""
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return self._iter().one_or_none()
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def all(self):
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"""Return all rows.
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Equivalent to :meth:`_query.Query.all`.
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"""
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return self._iter().all()
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def get(self, ident):
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"""Retrieve an object based on identity.
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Equivalent to :meth:`_query.Query.get`.
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"""
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query = self.bq.steps[0](self.session)
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return query._get_impl(ident, self._load_on_pk_identity)
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def _load_on_pk_identity(self, session, query, primary_key_identity, **kw):
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"""Load the given primary key identity from the database."""
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mapper = query._raw_columns[0]._annotations["parententity"]
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_get_clause, _get_params = mapper._get_clause
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def setup(query):
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_lcl_get_clause = _get_clause
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q = query._clone()
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q._get_condition()
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q._order_by = None
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# None present in ident - turn those comparisons
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# into "IS NULL"
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if None in primary_key_identity:
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nones = {
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_get_params[col].key
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for col, value in zip(
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mapper.primary_key, primary_key_identity
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)
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if value is None
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}
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_lcl_get_clause = sql_util.adapt_criterion_to_null(
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_lcl_get_clause, nones
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)
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# TODO: can mapper._get_clause be pre-adapted?
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q._where_criteria = (
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sql_util._deep_annotate(_lcl_get_clause, {"_orm_adapt": True}),
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)
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for fn in self._post_criteria:
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q = fn(q)
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return q
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# cache the query against a key that includes
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# which positions in the primary key are NULL
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# (remember, we can map to an OUTER JOIN)
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bq = self.bq
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# add the clause we got from mapper._get_clause to the cache
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# key so that if a race causes multiple calls to _get_clause,
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# we've cached on ours
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bq = bq._clone()
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bq._cache_key += (_get_clause,)
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bq = bq.with_criteria(
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setup, tuple(elem is None for elem in primary_key_identity)
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)
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params = {
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_get_params[primary_key].key: id_val
|
|
for id_val, primary_key in zip(
|
|
primary_key_identity, mapper.primary_key
|
|
)
|
|
}
|
|
|
|
result = list(bq.for_session(self.session).params(**params))
|
|
l = len(result)
|
|
if l > 1:
|
|
raise orm_exc.MultipleResultsFound()
|
|
elif l:
|
|
return result[0]
|
|
else:
|
|
return None
|
|
|
|
|
|
bakery = BakedQuery.bakery
|