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Diffstat (limited to 'lib/sqlalchemy/sql/cache_key.py')
| -rw-r--r-- | lib/sqlalchemy/sql/cache_key.py | 762 |
1 files changed, 762 insertions, 0 deletions
diff --git a/lib/sqlalchemy/sql/cache_key.py b/lib/sqlalchemy/sql/cache_key.py new file mode 100644 index 000000000..8dd44dbf0 --- /dev/null +++ b/lib/sqlalchemy/sql/cache_key.py @@ -0,0 +1,762 @@ +# sql/cache_key.py +# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors +# <see AUTHORS file> +# +# This module is part of SQLAlchemy and is released under +# the MIT License: https://www.opensource.org/licenses/mit-license.php + +from collections import namedtuple +import enum +from itertools import zip_longest +from typing import Callable +from typing import Union + +from .visitors import anon_map +from .visitors import ExtendedInternalTraversal +from .visitors import InternalTraversal +from .. import util +from ..inspection import inspect +from ..util import HasMemoized +from ..util.typing import Literal + + +class CacheConst(enum.Enum): + NO_CACHE = 0 + + +NO_CACHE = CacheConst.NO_CACHE + + +class CacheTraverseTarget(enum.Enum): + CACHE_IN_PLACE = 0 + CALL_GEN_CACHE_KEY = 1 + STATIC_CACHE_KEY = 2 + PROPAGATE_ATTRS = 3 + ANON_NAME = 4 + + +( + CACHE_IN_PLACE, + CALL_GEN_CACHE_KEY, + STATIC_CACHE_KEY, + PROPAGATE_ATTRS, + ANON_NAME, +) = tuple(CacheTraverseTarget) + + +class HasCacheKey: + """Mixin for objects which can produce a cache key. + + .. seealso:: + + :class:`.CacheKey` + + :ref:`sql_caching` + + """ + + _cache_key_traversal = NO_CACHE + + _is_has_cache_key = True + + _hierarchy_supports_caching = True + """private attribute which may be set to False to prevent the + inherit_cache warning from being emitted for a hierarchy of subclasses. + + Currently applies to the DDLElement hierarchy which does not implement + caching. + + """ + + inherit_cache = None + """Indicate if this :class:`.HasCacheKey` instance should make use of the + cache key generation scheme used by its immediate superclass. + + The attribute defaults to ``None``, which indicates that a construct has + not yet taken into account whether or not its appropriate for it to + participate in caching; this is functionally equivalent to setting the + value to ``False``, except that a warning is also emitted. + + This flag can be set to ``True`` on a particular class, if the SQL that + corresponds to the object does not change based on attributes which + are local to this class, and not its superclass. + + .. seealso:: + + :ref:`compilerext_caching` - General guideslines for setting the + :attr:`.HasCacheKey.inherit_cache` attribute for third-party or user + defined SQL constructs. + + """ + + __slots__ = () + + @classmethod + def _generate_cache_attrs(cls): + """generate cache key dispatcher for a new class. + + This sets the _generated_cache_key_traversal attribute once called + so should only be called once per class. + + """ + inherit_cache = cls.__dict__.get("inherit_cache", None) + inherit = bool(inherit_cache) + + if inherit: + _cache_key_traversal = getattr(cls, "_cache_key_traversal", None) + if _cache_key_traversal is None: + try: + _cache_key_traversal = cls._traverse_internals + except AttributeError: + cls._generated_cache_key_traversal = NO_CACHE + return NO_CACHE + + # TODO: wouldn't we instead get this from our superclass? + # also, our superclass may not have this yet, but in any case, + # we'd generate for the superclass that has it. this is a little + # more complicated, so for the moment this is a little less + # efficient on startup but simpler. + return _cache_key_traversal_visitor.generate_dispatch( + cls, _cache_key_traversal, "_generated_cache_key_traversal" + ) + else: + _cache_key_traversal = cls.__dict__.get( + "_cache_key_traversal", None + ) + if _cache_key_traversal is None: + _cache_key_traversal = cls.__dict__.get( + "_traverse_internals", None + ) + if _cache_key_traversal is None: + cls._generated_cache_key_traversal = NO_CACHE + if ( + inherit_cache is None + and cls._hierarchy_supports_caching + ): + util.warn( + "Class %s will not make use of SQL compilation " + "caching as it does not set the 'inherit_cache' " + "attribute to ``True``. This can have " + "significant performance implications including " + "some performance degradations in comparison to " + "prior SQLAlchemy versions. Set this attribute " + "to True if this object can make use of the cache " + "key generated by the superclass. Alternatively, " + "this attribute may be set to False which will " + "disable this warning." % (cls.__name__), + code="cprf", + ) + return NO_CACHE + + return _cache_key_traversal_visitor.generate_dispatch( + cls, _cache_key_traversal, "_generated_cache_key_traversal" + ) + + @util.preload_module("sqlalchemy.sql.elements") + def _gen_cache_key(self, anon_map, bindparams): + """return an optional cache key. + + The cache key is a tuple which can contain any series of + objects that are hashable and also identifies + this object uniquely within the presence of a larger SQL expression + or statement, for the purposes of caching the resulting query. + + The cache key should be based on the SQL compiled structure that would + ultimately be produced. That is, two structures that are composed in + exactly the same way should produce the same cache key; any difference + in the structures that would affect the SQL string or the type handlers + should result in a different cache key. + + If a structure cannot produce a useful cache key, the NO_CACHE + symbol should be added to the anon_map and the method should + return None. + + """ + + cls = self.__class__ + + id_, found = anon_map.get_anon(self) + if found: + return (id_, cls) + + dispatcher: Union[ + Literal[CacheConst.NO_CACHE], + Callable[[HasCacheKey, "_CacheKeyTraversal"], "CacheKey"], + ] + + try: + dispatcher = cls.__dict__["_generated_cache_key_traversal"] + except KeyError: + # most of the dispatchers are generated up front + # in sqlalchemy/sql/__init__.py -> + # traversals.py-> _preconfigure_traversals(). + # this block will generate any remaining dispatchers. + dispatcher = cls._generate_cache_attrs() + + if dispatcher is NO_CACHE: + anon_map[NO_CACHE] = True + return None + + result = (id_, cls) + + # inline of _cache_key_traversal_visitor.run_generated_dispatch() + + for attrname, obj, meth in dispatcher( + self, _cache_key_traversal_visitor + ): + if obj is not None: + # TODO: see if C code can help here as Python lacks an + # efficient switch construct + + if meth is STATIC_CACHE_KEY: + sck = obj._static_cache_key + if sck is NO_CACHE: + anon_map[NO_CACHE] = True + return None + result += (attrname, sck) + elif meth is ANON_NAME: + elements = util.preloaded.sql_elements + if isinstance(obj, elements._anonymous_label): + obj = obj.apply_map(anon_map) + result += (attrname, obj) + elif meth is CALL_GEN_CACHE_KEY: + result += ( + attrname, + obj._gen_cache_key(anon_map, bindparams), + ) + + # remaining cache functions are against + # Python tuples, dicts, lists, etc. so we can skip + # if they are empty + elif obj: + if meth is CACHE_IN_PLACE: + result += (attrname, obj) + elif meth is PROPAGATE_ATTRS: + result += ( + attrname, + obj["compile_state_plugin"], + obj["plugin_subject"]._gen_cache_key( + anon_map, bindparams + ) + if obj["plugin_subject"] + else None, + ) + elif meth is InternalTraversal.dp_annotations_key: + # obj is here is the _annotations dict. however, we + # want to use the memoized cache key version of it. for + # Columns, this should be long lived. For select() + # statements, not so much, but they usually won't have + # annotations. + result += self._annotations_cache_key + elif ( + meth is InternalTraversal.dp_clauseelement_list + or meth is InternalTraversal.dp_clauseelement_tuple + or meth + is InternalTraversal.dp_memoized_select_entities + ): + result += ( + attrname, + tuple( + [ + elem._gen_cache_key(anon_map, bindparams) + for elem in obj + ] + ), + ) + else: + result += meth( + attrname, obj, self, anon_map, bindparams + ) + return result + + def _generate_cache_key(self): + """return a cache key. + + The cache key is a tuple which can contain any series of + objects that are hashable and also identifies + this object uniquely within the presence of a larger SQL expression + or statement, for the purposes of caching the resulting query. + + The cache key should be based on the SQL compiled structure that would + ultimately be produced. That is, two structures that are composed in + exactly the same way should produce the same cache key; any difference + in the structures that would affect the SQL string or the type handlers + should result in a different cache key. + + The cache key returned by this method is an instance of + :class:`.CacheKey`, which consists of a tuple representing the + cache key, as well as a list of :class:`.BindParameter` objects + which are extracted from the expression. While two expressions + that produce identical cache key tuples will themselves generate + identical SQL strings, the list of :class:`.BindParameter` objects + indicates the bound values which may have different values in + each one; these bound parameters must be consulted in order to + execute the statement with the correct parameters. + + a :class:`_expression.ClauseElement` structure that does not implement + a :meth:`._gen_cache_key` method and does not implement a + :attr:`.traverse_internals` attribute will not be cacheable; when + such an element is embedded into a larger structure, this method + will return None, indicating no cache key is available. + + """ + + bindparams = [] + + _anon_map = anon_map() + key = self._gen_cache_key(_anon_map, bindparams) + if NO_CACHE in _anon_map: + return None + else: + return CacheKey(key, bindparams) + + @classmethod + def _generate_cache_key_for_object(cls, obj): + bindparams = [] + + _anon_map = anon_map() + key = obj._gen_cache_key(_anon_map, bindparams) + if NO_CACHE in _anon_map: + return None + else: + return CacheKey(key, bindparams) + + +class MemoizedHasCacheKey(HasCacheKey, HasMemoized): + @HasMemoized.memoized_instancemethod + def _generate_cache_key(self): + return HasCacheKey._generate_cache_key(self) + + +class CacheKey(namedtuple("CacheKey", ["key", "bindparams"])): + """The key used to identify a SQL statement construct in the + SQL compilation cache. + + .. seealso:: + + :ref:`sql_caching` + + """ + + def __hash__(self): + """CacheKey itself is not hashable - hash the .key portion""" + + return None + + def to_offline_string(self, statement_cache, statement, parameters): + """Generate an "offline string" form of this :class:`.CacheKey` + + The "offline string" is basically the string SQL for the + statement plus a repr of the bound parameter values in series. + Whereas the :class:`.CacheKey` object is dependent on in-memory + identities in order to work as a cache key, the "offline" version + is suitable for a cache that will work for other processes as well. + + The given ``statement_cache`` is a dictionary-like object where the + string form of the statement itself will be cached. This dictionary + should be in a longer lived scope in order to reduce the time spent + stringifying statements. + + + """ + if self.key not in statement_cache: + statement_cache[self.key] = sql_str = str(statement) + else: + sql_str = statement_cache[self.key] + + if not self.bindparams: + param_tuple = tuple(parameters[key] for key in sorted(parameters)) + else: + param_tuple = tuple( + parameters.get(bindparam.key, bindparam.value) + for bindparam in self.bindparams + ) + + return repr((sql_str, param_tuple)) + + def __eq__(self, other): + return self.key == other.key + + @classmethod + def _diff_tuples(cls, left, right): + ck1 = CacheKey(left, []) + ck2 = CacheKey(right, []) + return ck1._diff(ck2) + + def _whats_different(self, other): + + k1 = self.key + k2 = other.key + + stack = [] + pickup_index = 0 + while True: + s1, s2 = k1, k2 + for idx in stack: + s1 = s1[idx] + s2 = s2[idx] + + for idx, (e1, e2) in enumerate(zip_longest(s1, s2)): + if idx < pickup_index: + continue + if e1 != e2: + if isinstance(e1, tuple) and isinstance(e2, tuple): + stack.append(idx) + break + else: + yield "key%s[%d]: %s != %s" % ( + "".join("[%d]" % id_ for id_ in stack), + idx, + e1, + e2, + ) + else: + pickup_index = stack.pop(-1) + break + + def _diff(self, other): + return ", ".join(self._whats_different(other)) + + def __str__(self): + stack = [self.key] + + output = [] + sentinel = object() + indent = -1 + while stack: + elem = stack.pop(0) + if elem is sentinel: + output.append((" " * (indent * 2)) + "),") + indent -= 1 + elif isinstance(elem, tuple): + if not elem: + output.append((" " * ((indent + 1) * 2)) + "()") + else: + indent += 1 + stack = list(elem) + [sentinel] + stack + output.append((" " * (indent * 2)) + "(") + else: + if isinstance(elem, HasCacheKey): + repr_ = "<%s object at %s>" % ( + type(elem).__name__, + hex(id(elem)), + ) + else: + repr_ = repr(elem) + output.append((" " * (indent * 2)) + " " + repr_ + ", ") + + return "CacheKey(key=%s)" % ("\n".join(output),) + + def _generate_param_dict(self): + """used for testing""" + + from .compiler import prefix_anon_map + + _anon_map = prefix_anon_map() + return {b.key % _anon_map: b.effective_value for b in self.bindparams} + + def _apply_params_to_element(self, original_cache_key, target_element): + translate = { + k.key: v.value + for k, v in zip(original_cache_key.bindparams, self.bindparams) + } + + return target_element.params(translate) + + +class _CacheKeyTraversal(ExtendedInternalTraversal): + # very common elements are inlined into the main _get_cache_key() method + # to produce a dramatic savings in Python function call overhead + + visit_has_cache_key = visit_clauseelement = CALL_GEN_CACHE_KEY + visit_clauseelement_list = InternalTraversal.dp_clauseelement_list + visit_annotations_key = InternalTraversal.dp_annotations_key + visit_clauseelement_tuple = InternalTraversal.dp_clauseelement_tuple + visit_memoized_select_entities = ( + InternalTraversal.dp_memoized_select_entities + ) + + visit_string = ( + visit_boolean + ) = visit_operator = visit_plain_obj = CACHE_IN_PLACE + visit_statement_hint_list = CACHE_IN_PLACE + visit_type = STATIC_CACHE_KEY + visit_anon_name = ANON_NAME + + visit_propagate_attrs = PROPAGATE_ATTRS + + def visit_with_context_options( + self, attrname, obj, parent, anon_map, bindparams + ): + return tuple((fn.__code__, c_key) for fn, c_key in obj) + + def visit_inspectable(self, attrname, obj, parent, anon_map, bindparams): + return (attrname, inspect(obj)._gen_cache_key(anon_map, bindparams)) + + def visit_string_list(self, attrname, obj, parent, anon_map, bindparams): + return tuple(obj) + + def visit_multi(self, attrname, obj, parent, anon_map, bindparams): + return ( + attrname, + obj._gen_cache_key(anon_map, bindparams) + if isinstance(obj, HasCacheKey) + else obj, + ) + + def visit_multi_list(self, attrname, obj, parent, anon_map, bindparams): + return ( + attrname, + tuple( + elem._gen_cache_key(anon_map, bindparams) + if isinstance(elem, HasCacheKey) + else elem + for elem in obj + ), + ) + + def visit_has_cache_key_tuples( + self, attrname, obj, parent, anon_map, bindparams + ): + if not obj: + return () + return ( + attrname, + tuple( + tuple( + elem._gen_cache_key(anon_map, bindparams) + for elem in tup_elem + ) + for tup_elem in obj + ), + ) + + def visit_has_cache_key_list( + self, attrname, obj, parent, anon_map, bindparams + ): + if not obj: + return () + return ( + attrname, + tuple(elem._gen_cache_key(anon_map, bindparams) for elem in obj), + ) + + def visit_executable_options( + self, attrname, obj, parent, anon_map, bindparams + ): + if not obj: + return () + return ( + attrname, + tuple( + elem._gen_cache_key(anon_map, bindparams) + for elem in obj + if elem._is_has_cache_key + ), + ) + + def visit_inspectable_list( + self, attrname, obj, parent, anon_map, bindparams + ): + return self.visit_has_cache_key_list( + attrname, [inspect(o) for o in obj], parent, anon_map, bindparams + ) + + def visit_clauseelement_tuples( + self, attrname, obj, parent, anon_map, bindparams + ): + return self.visit_has_cache_key_tuples( + attrname, obj, parent, anon_map, bindparams + ) + + def visit_fromclause_ordered_set( + self, attrname, obj, parent, anon_map, bindparams + ): + if not obj: + return () + return ( + attrname, + tuple([elem._gen_cache_key(anon_map, bindparams) for elem in obj]), + ) + + def visit_clauseelement_unordered_set( + self, attrname, obj, parent, anon_map, bindparams + ): + if not obj: + return () + cache_keys = [ + elem._gen_cache_key(anon_map, bindparams) for elem in obj + ] + return ( + attrname, + tuple( + sorted(cache_keys) + ), # cache keys all start with (id_, class) + ) + + def visit_named_ddl_element( + self, attrname, obj, parent, anon_map, bindparams + ): + return (attrname, obj.name) + + def visit_prefix_sequence( + self, attrname, obj, parent, anon_map, bindparams + ): + if not obj: + return () + + return ( + attrname, + tuple( + [ + (clause._gen_cache_key(anon_map, bindparams), strval) + for clause, strval in obj + ] + ), + ) + + def visit_setup_join_tuple( + self, attrname, obj, parent, anon_map, bindparams + ): + return tuple( + ( + target._gen_cache_key(anon_map, bindparams), + onclause._gen_cache_key(anon_map, bindparams) + if onclause is not None + else None, + from_._gen_cache_key(anon_map, bindparams) + if from_ is not None + else None, + tuple([(key, flags[key]) for key in sorted(flags)]), + ) + for (target, onclause, from_, flags) in obj + ) + + def visit_table_hint_list( + self, attrname, obj, parent, anon_map, bindparams + ): + if not obj: + return () + + return ( + attrname, + tuple( + [ + ( + clause._gen_cache_key(anon_map, bindparams), + dialect_name, + text, + ) + for (clause, dialect_name), text in obj.items() + ] + ), + ) + + def visit_plain_dict(self, attrname, obj, parent, anon_map, bindparams): + return (attrname, tuple([(key, obj[key]) for key in sorted(obj)])) + + def visit_dialect_options( + self, attrname, obj, parent, anon_map, bindparams + ): + return ( + attrname, + tuple( + ( + dialect_name, + tuple( + [ + (key, obj[dialect_name][key]) + for key in sorted(obj[dialect_name]) + ] + ), + ) + for dialect_name in sorted(obj) + ), + ) + + def visit_string_clauseelement_dict( + self, attrname, obj, parent, anon_map, bindparams + ): + return ( + attrname, + tuple( + (key, obj[key]._gen_cache_key(anon_map, bindparams)) + for key in sorted(obj) + ), + ) + + def visit_string_multi_dict( + self, attrname, obj, parent, anon_map, bindparams + ): + return ( + attrname, + tuple( + ( + key, + value._gen_cache_key(anon_map, bindparams) + if isinstance(value, HasCacheKey) + else value, + ) + for key, value in [(key, obj[key]) for key in sorted(obj)] + ), + ) + + def visit_fromclause_canonical_column_collection( + self, attrname, obj, parent, anon_map, bindparams + ): + # inlining into the internals of ColumnCollection + return ( + attrname, + tuple( + col._gen_cache_key(anon_map, bindparams) + for k, col in obj._collection + ), + ) + + def visit_unknown_structure( + self, attrname, obj, parent, anon_map, bindparams + ): + anon_map[NO_CACHE] = True + return () + + def visit_dml_ordered_values( + self, attrname, obj, parent, anon_map, bindparams + ): + return ( + attrname, + tuple( + ( + key._gen_cache_key(anon_map, bindparams) + if hasattr(key, "__clause_element__") + else key, + value._gen_cache_key(anon_map, bindparams), + ) + for key, value in obj + ), + ) + + def visit_dml_values(self, attrname, obj, parent, anon_map, bindparams): + # in py37 we can assume two dictionaries created in the same + # insert ordering will retain that sorting + return ( + attrname, + tuple( + ( + k._gen_cache_key(anon_map, bindparams) + if hasattr(k, "__clause_element__") + else k, + obj[k]._gen_cache_key(anon_map, bindparams), + ) + for k in obj + ), + ) + + def visit_dml_multi_values( + self, attrname, obj, parent, anon_map, bindparams + ): + # multivalues are simply not cacheable right now + anon_map[NO_CACHE] = True + return () + + +_cache_key_traversal_visitor = _CacheKeyTraversal() |