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# sqlalchemy/ext/baked.py
# Copyright (C) 2005-2016 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""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.
"""
from ..orm.query import Query
from ..orm import strategies, attributes, properties, \
strategy_options, util as orm_util, interfaces
from .. import log as sqla_log
from ..sql import util as sql_util
from ..orm import exc as orm_exc
from .. import exc as sa_exc
from .. import util
import copy
import logging
log = logging.getLogger(__name__)
class BakedQuery(object):
"""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):
"""Construct a new bakery."""
_bakery = util.LRUCache(size)
def call(initial_fn, *args):
return cls(_bakery, initial_fn, args)
return call
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:`.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` object is built from scratch each
time, with all creational functions being called on each
invocation.
"""
if not full:
_spoil_point = self._clone()
_spoil_point._cache_key += ('_query_only', )
self.steps = [_spoil_point._retrieve_baked_query]
self._spoiled = True
return self
def _retrieve_baked_query(self, session):
query = self._bakery.get(self._cache_key, None)
if query is None:
query = self._as_query(session)
self._bakery[self._cache_key] = query.with_session(None)
return query.with_session(session)
def _bake(self, session):
query = self._as_query(session)
context = query._compile_context()
self._bake_subquery_loaders(session, context)
context.session = None
context.query = query = context.query.with_session(None)
query._execution_options = query._execution_options.union(
{"compiled_cache": self._bakery}
)
# we'll be holding onto the query for some of its state,
# so delete some compilation-use-only attributes that can take up
# space
for attr in (
'_correlate', '_from_obj', '_mapper_adapter_map',
'_joinpath', '_joinpoint'):
query.__dict__.pop(attr, None)
self._bakery[self._cache_key] = context
return context
def _as_query(self, session):
query = self.steps[0](session)
for step in self.steps[1:]:
query = step(query)
return query
def _bake_subquery_loaders(self, session, context):
"""convert subquery eager loaders in the cache into baked queries.
For subquery eager loading to work, all we need here is that the
Query point to the correct session when it is run. However, since
we are "baking" anyway, we may as well also turn the query into
a "baked" query so that we save on performance too.
"""
context.attributes['baked_queries'] = baked_queries = []
for k, v in list(context.attributes.items()):
if isinstance(v, Query):
if 'subquery' in k:
bk = BakedQuery(self._bakery, lambda *args: v)
bk._cache_key = self._cache_key + k
bk._bake(session)
baked_queries.append((k, bk._cache_key, v))
del context.attributes[k]
def _unbake_subquery_loaders(self, session, context, params):
"""Retrieve subquery eager loaders stored by _bake_subquery_loaders
and turn them back into Result objects that will iterate just
like a Query object.
"""
for k, cache_key, query in context.attributes["baked_queries"]:
bk = BakedQuery(self._bakery,
lambda sess, q=query: q.with_session(sess))
bk._cache_key = cache_key
context.attributes[k] = bk.for_session(session).params(**params)
class Result(object):
"""Invokes a :class:`.BakedQuery` against a :class:`.Session`.
The :class:`.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'
def __init__(self, bq, session):
self.bq = bq
self.session = session
self._params = {}
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 _as_query(self):
return self.bq._as_query(self.session).params(self._params)
def __str__(self):
return str(self._as_query())
def __iter__(self):
bq = self.bq
if bq._spoiled:
return iter(self._as_query())
baked_context = bq._bakery.get(bq._cache_key, None)
if baked_context is None:
baked_context = bq._bake(self.session)
context = copy.copy(baked_context)
context.session = self.session
context.attributes = context.attributes.copy()
bq._unbake_subquery_loaders(self.session, context, self._params)
context.statement.use_labels = True
if context.autoflush and not context.populate_existing:
self.session._autoflush()
return context.query.params(self._params).\
with_session(self.session)._execute_and_instances(context)
def first(self):
"""Return the first row.
Equivalent to :meth:`.Query.first`.
"""
bq = self.bq.with_criteria(lambda q: q.slice(0, 1))
ret = list(bq.for_session(self.session).params(self._params))
if len(ret) > 0:
return ret[0]
else:
return None
def one(self):
"""Return exactly one result or raise an exception.
Equivalent to :meth:`.Query.one`.
"""
ret = list(self)
l = len(ret)
if l == 1:
return ret[0]
elif l == 0:
raise orm_exc.NoResultFound("No row was found for one()")
else:
raise orm_exc.MultipleResultsFound(
"Multiple rows were found for one()")
def one_or_none(self):
"""Return one or zero results, or raise an exception for multiple
rows.
Equivalent to :meth:`.Query.one_or_none`.
.. versionadded:: 1.0.9
"""
ret = list(self)
l = len(ret)
if l == 1:
return ret[0]
elif l == 0:
return None
else:
raise orm_exc.MultipleResultsFound(
"Multiple rows were found for one_or_none()")
def all(self):
"""Return all rows.
Equivalent to :meth:`.Query.all`.
"""
return list(self)
def get(self, ident):
"""Retrieve an object based on identity.
Equivalent to :meth:`.Query.get`.
"""
query = self.bq.steps[0](self.session)
return query._get_impl(ident, self._load_on_ident)
def _load_on_ident(self, query, key):
"""Load the given identity key from the database."""
ident = key[1]
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 ident:
nones = set([
_get_params[col].key for col, value in
zip(mapper.primary_key, ident) 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
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 ident))
params = dict([
(_get_params[primary_key].key, id_val)
for id_val, primary_key in zip(ident, 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
def bake_lazy_loaders():
"""Enable the use of baked queries for all lazyloaders systemwide.
This operation should be safe for all lazy loaders, and will reduce
Python overhead for these operations.
"""
BakedLazyLoader._strategy_keys[:] = []
properties.RelationshipProperty.strategy_for(
lazy="select")(BakedLazyLoader)
properties.RelationshipProperty.strategy_for(
lazy=True)(BakedLazyLoader)
properties.RelationshipProperty.strategy_for(
lazy="baked_select")(BakedLazyLoader)
strategies.LazyLoader._strategy_keys[:] = BakedLazyLoader._strategy_keys[:]
def unbake_lazy_loaders():
"""Disable the use of baked queries for all lazyloaders systemwide.
This operation reverts the changes produced by :func:`.bake_lazy_loaders`.
"""
strategies.LazyLoader._strategy_keys[:] = []
BakedLazyLoader._strategy_keys[:] = []
properties.RelationshipProperty.strategy_for(
lazy="select")(strategies.LazyLoader)
properties.RelationshipProperty.strategy_for(
lazy=True)(strategies.LazyLoader)
properties.RelationshipProperty.strategy_for(
lazy="baked_select")(BakedLazyLoader)
assert strategies.LazyLoader._strategy_keys
@sqla_log.class_logger
@properties.RelationshipProperty.strategy_for(lazy="baked_select")
class BakedLazyLoader(strategies.LazyLoader):
def _emit_lazyload(self, session, state, ident_key, passive):
q = BakedQuery(
self.mapper._compiled_cache,
lambda session: session.query(self.mapper))
q.add_criteria(
lambda q: q._adapt_all_clauses()._with_invoke_all_eagers(False),
self.parent_property)
if not self.parent_property.bake_queries:
q.spoil(full=True)
if self.parent_property.secondary is not None:
q.add_criteria(
lambda q:
q.select_from(self.mapper, self.parent_property.secondary))
pending = not state.key
# don't autoflush on pending
if pending or passive & attributes.NO_AUTOFLUSH:
q.add_criteria(lambda q: q.autoflush(False))
if state.load_path:
q.spoil()
q.add_criteria(
lambda q:
q._with_current_path(state.load_path[self.parent_property]))
if state.load_options:
q.spoil()
q.add_criteria(
lambda q: q._conditional_options(*state.load_options))
if self.use_get:
return q(session)._load_on_ident(
session.query(self.mapper), ident_key)
if self.parent_property.order_by:
q.add_criteria(
lambda q:
q.order_by(*util.to_list(self.parent_property.order_by)))
for rev in self.parent_property._reverse_property:
# reverse props that are MANYTOONE are loading *this*
# object from get(), so don't need to eager out to those.
if rev.direction is interfaces.MANYTOONE and \
rev._use_get and \
not isinstance(rev.strategy, strategies.LazyLoader):
q.add_criteria(
lambda q:
q.options(
strategy_options.Load(
rev.parent).baked_lazyload(rev.key)))
lazy_clause, params = self._generate_lazy_clause(state, passive)
if pending:
if orm_util._none_set.intersection(params.values()):
return None
q.add_criteria(lambda q: q.filter(lazy_clause))
result = q(session).params(**params).all()
if self.uselist:
return result
else:
l = len(result)
if l:
if l > 1:
util.warn(
"Multiple rows returned with "
"uselist=False for lazily-loaded attribute '%s' "
% self.parent_property)
return result[0]
else:
return None
@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
def baked_lazyload(*keys):
return strategy_options._UnboundLoad._from_keys(
strategy_options._UnboundLoad.baked_lazyload, keys, False, {})
@baked_lazyload._add_unbound_all_fn
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
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