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