692 lines
21 KiB
Python
692 lines
21 KiB
Python
# sqlalchemy/ext/baked.py
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# Copyright (C) 2005-2020 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: http://www.opensource.org/licenses/mit-license.php
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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 copy
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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 import strategy_options
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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(object):
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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(object):
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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 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:`.Result` object for this :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` 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` object is part of what's cached
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and needs to match the type of :class:`.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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"""
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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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if cache_path.path[0].is_aliased_class:
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# paths that are against an AliasedClass are unsafe to cache
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# with since the AliasedClass is an ad-hoc object.
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self.spoil()
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else:
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for opt in options:
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cache_key = opt._generate_cache_key(cache_path)
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if cache_key is False:
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self.spoil()
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elif cache_key is not None:
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key += cache_key
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self.add_criteria(
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lambda q: q._with_current_path(
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effective_path
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)._conditional_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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context = query._compile_context()
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self._bake_subquery_loaders(session, context)
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context.session = None
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context.query = query = context.query.with_session(None)
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query._execution_options = query._execution_options.union(
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{"compiled_cache": self._bakery}
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)
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# we'll be holding onto the query for some of its state,
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# so delete some compilation-use-only attributes that can take up
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# space
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for attr in (
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"_correlate",
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"_from_obj",
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"_mapper_adapter_map",
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"_joinpath",
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"_joinpoint",
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):
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query.__dict__.pop(attr, None)
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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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if context.query._bake_ok:
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self._bakery[self._effective_key(session)] = context
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return context
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def to_query(self, query_or_session):
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"""Return the :class:`.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` 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(Address.id, sub_bq.to_query(q).as_scalar())
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)
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:param query_or_session: a :class:`.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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def _bake_subquery_loaders(self, session, context):
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"""convert subquery eager loaders in the cache into baked queries.
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For subquery eager loading to work, all we need here is that the
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Query point to the correct session when it is run. However, since
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we are "baking" anyway, we may as well also turn the query into
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a "baked" query so that we save on performance too.
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"""
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context.attributes["baked_queries"] = baked_queries = []
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for k, v in list(context.attributes.items()):
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if isinstance(v, Query):
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if "subquery" in k:
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bk = BakedQuery(self._bakery, lambda *args: v)
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bk._cache_key = self._cache_key + k
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bk._bake(session)
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baked_queries.append((k, bk._cache_key, v))
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del context.attributes[k]
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def _unbake_subquery_loaders(
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self, session, context, params, post_criteria
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):
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"""Retrieve subquery eager loaders stored by _bake_subquery_loaders
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and turn them back into Result objects that will iterate just
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like a Query object.
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"""
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if "baked_queries" not in context.attributes:
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return
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for k, cache_key, query in context.attributes["baked_queries"]:
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bk = BakedQuery(
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self._bakery, lambda sess, q=query: q.with_session(sess)
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)
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bk._cache_key = cache_key
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q = bk.for_session(session)
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for fn in post_criteria:
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q = q.with_post_criteria(fn)
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context.attributes[k] = q.params(**params)
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class Result(object):
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"""Invokes a :class:`.BakedQuery` against a :class:`.Session`.
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The :class:`.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` object after it is retrieved from the
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cache. Functions here can be used to alter the query in ways
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that **do not affect the SQL output**, such as execution options
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and shard identifiers (when using a shard-enabled query object)
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.. warning:: :meth:`.Result.with_post_criteria` functions are applied
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to the :class:`.Query` object **after** the query's SQL statement
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object has been retrieved from the cache. Any operations here
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which intend to modify the SQL should ensure that
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:meth:`.BakedQuery.spoil` was called first.
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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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bq = self.bq
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if not self.session.enable_baked_queries or bq._spoiled:
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return iter(self._as_query())
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baked_context = bq._bakery.get(bq._effective_key(self.session), None)
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if baked_context is None:
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baked_context = bq._bake(self.session)
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context = copy.copy(baked_context)
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context.session = self.session
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context.attributes = context.attributes.copy()
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bq._unbake_subquery_loaders(
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self.session, context, self._params, self._post_criteria
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)
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context.statement.use_labels = True
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if context.autoflush and not context.populate_existing:
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self.session._autoflush()
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q = context.query.params(self._params).with_session(self.session)
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for fn in self._post_criteria:
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q = fn(q)
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return q._execute_and_instances(context)
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def count(self):
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"""return the 'count'.
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Equivalent to :meth:`.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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.. versionadded:: 1.1.6
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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.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.scalar`.
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.. versionadded:: 1.1.6
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"""
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try:
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ret = self.one()
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if not isinstance(ret, tuple):
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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.first`.
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"""
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bq = self.bq.with_criteria(lambda q: q.slice(0, 1))
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ret = list(
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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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)
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if len(ret) > 0:
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return ret[0]
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else:
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return None
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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.one`.
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"""
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try:
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ret = self.one_or_none()
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except orm_exc.MultipleResultsFound as err:
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util.raise_(
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orm_exc.MultipleResultsFound(
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"Multiple rows were found for one()"
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),
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replace_context=err,
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)
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else:
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if ret is None:
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raise orm_exc.NoResultFound("No row was found for one()")
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return ret
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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.one_or_none`.
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.. versionadded:: 1.0.9
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"""
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ret = list(self)
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l = len(ret)
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if l == 1:
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return ret[0]
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elif l == 0:
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return None
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else:
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raise orm_exc.MultipleResultsFound(
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"Multiple rows were found for one_or_none()"
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)
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def all(self):
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"""Return all rows.
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Equivalent to :meth:`.Query.all`.
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"""
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return list(self)
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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.get`.
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|
|
"""
|
|
|
|
query = self.bq.steps[0](self.session)
|
|
return query._get_impl(ident, self._load_on_pk_identity)
|
|
|
|
def _load_on_pk_identity(self, query, primary_key_identity):
|
|
"""Load the given primary key identity from the database."""
|
|
|
|
mapper = query._mapper_zero()
|
|
|
|
_get_clause, _get_params = mapper._get_clause
|
|
|
|
def setup(query):
|
|
_lcl_get_clause = _get_clause
|
|
q = query._clone()
|
|
q._get_condition()
|
|
q._order_by = None
|
|
|
|
# None present in ident - turn those comparisons
|
|
# into "IS NULL"
|
|
if None in primary_key_identity:
|
|
nones = set(
|
|
[
|
|
_get_params[col].key
|
|
for col, value in zip(
|
|
mapper.primary_key, primary_key_identity
|
|
)
|
|
if value is None
|
|
]
|
|
)
|
|
_lcl_get_clause = sql_util.adapt_criterion_to_null(
|
|
_lcl_get_clause, nones
|
|
)
|
|
|
|
_lcl_get_clause = q._adapt_clause(_lcl_get_clause, True, False)
|
|
q._criterion = _lcl_get_clause
|
|
for fn in self._post_criteria:
|
|
q = fn(q)
|
|
return q
|
|
|
|
# cache the query against a key that includes
|
|
# which positions in the primary key are NULL
|
|
# (remember, we can map to an OUTER JOIN)
|
|
bq = self.bq
|
|
|
|
# add the clause we got from mapper._get_clause to the cache
|
|
# key so that if a race causes multiple calls to _get_clause,
|
|
# we've cached on ours
|
|
bq = bq._clone()
|
|
bq._cache_key += (_get_clause,)
|
|
|
|
bq = bq.with_criteria(
|
|
setup, tuple(elem is None for elem in primary_key_identity)
|
|
)
|
|
|
|
params = dict(
|
|
[
|
|
(_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
|
|
|
|
|
|
@util.deprecated(
|
|
"1.2", "Baked lazy loading is now the default implementation."
|
|
)
|
|
def bake_lazy_loaders():
|
|
"""Enable the use of baked queries for all lazyloaders systemwide.
|
|
|
|
The "baked" implementation of lazy loading is now the sole implementation
|
|
for the base lazy loader; this method has no effect except for a warning.
|
|
|
|
"""
|
|
pass
|
|
|
|
|
|
@util.deprecated(
|
|
"1.2", "Baked lazy loading is now the default implementation."
|
|
)
|
|
def unbake_lazy_loaders():
|
|
"""Disable the use of baked queries for all lazyloaders systemwide.
|
|
|
|
This method now raises NotImplementedError() as the "baked" implementation
|
|
is the only lazy load implementation. The
|
|
:paramref:`.relationship.bake_queries` flag may be used to disable
|
|
the caching of queries on a per-relationship basis.
|
|
|
|
"""
|
|
raise NotImplementedError(
|
|
"Baked lazy loading is now the default implementation"
|
|
)
|
|
|
|
|
|
@strategy_options.loader_option()
|
|
def baked_lazyload(loadopt, attr):
|
|
"""Indicate that the given attribute should be loaded using "lazy"
|
|
loading with a "baked" query used in the load.
|
|
|
|
"""
|
|
return loadopt.set_relationship_strategy(attr, {"lazy": "baked_select"})
|
|
|
|
|
|
@baked_lazyload._add_unbound_fn
|
|
@util.deprecated(
|
|
"1.2",
|
|
"Baked lazy loading is now the default "
|
|
"implementation for lazy loading.",
|
|
)
|
|
def baked_lazyload(*keys):
|
|
return strategy_options._UnboundLoad._from_keys(
|
|
strategy_options._UnboundLoad.baked_lazyload, keys, False, {}
|
|
)
|
|
|
|
|
|
@baked_lazyload._add_unbound_all_fn
|
|
@util.deprecated(
|
|
"1.2",
|
|
"Baked lazy loading is now the default "
|
|
"implementation for lazy loading.",
|
|
)
|
|
def baked_lazyload_all(*keys):
|
|
return strategy_options._UnboundLoad._from_keys(
|
|
strategy_options._UnboundLoad.baked_lazyload, keys, True, {}
|
|
)
|
|
|
|
|
|
baked_lazyload = baked_lazyload._unbound_fn
|
|
baked_lazyload_all = baked_lazyload_all._unbound_all_fn
|
|
|
|
bakery = BakedQuery.bakery
|