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c66a06ac6b
This is in preparation for having multiple data stores that offer different functionality, e.g. splitting out state or event storage.
325 lines
11 KiB
Python
325 lines
11 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2014-2016 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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from six import iteritems, itervalues
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import attr
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from synapse.api.constants import EventTypes
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logger = logging.getLogger(__name__)
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@attr.s(slots=True)
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class StateFilter(object):
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"""A filter used when querying for state.
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Attributes:
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types (dict[str, set[str]|None]): Map from type to set of state keys (or
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None). This specifies which state_keys for the given type to fetch
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from the DB. If None then all events with that type are fetched. If
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the set is empty then no events with that type are fetched.
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include_others (bool): Whether to fetch events with types that do not
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appear in `types`.
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"""
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types = attr.ib()
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include_others = attr.ib(default=False)
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def __attrs_post_init__(self):
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# If `include_others` is set we canonicalise the filter by removing
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# wildcards from the types dictionary
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if self.include_others:
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self.types = {k: v for k, v in iteritems(self.types) if v is not None}
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@staticmethod
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def all():
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"""Creates a filter that fetches everything.
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Returns:
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StateFilter
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"""
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return StateFilter(types={}, include_others=True)
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@staticmethod
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def none():
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"""Creates a filter that fetches nothing.
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Returns:
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StateFilter
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"""
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return StateFilter(types={}, include_others=False)
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@staticmethod
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def from_types(types):
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"""Creates a filter that only fetches the given types
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Args:
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types (Iterable[tuple[str, str|None]]): A list of type and state
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keys to fetch. A state_key of None fetches everything for
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that type
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Returns:
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StateFilter
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"""
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type_dict = {}
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for typ, s in types:
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if typ in type_dict:
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if type_dict[typ] is None:
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continue
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if s is None:
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type_dict[typ] = None
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continue
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type_dict.setdefault(typ, set()).add(s)
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return StateFilter(types=type_dict)
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@staticmethod
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def from_lazy_load_member_list(members):
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"""Creates a filter that returns all non-member events, plus the member
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events for the given users
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Args:
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members (iterable[str]): Set of user IDs
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Returns:
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StateFilter
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"""
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return StateFilter(types={EventTypes.Member: set(members)}, include_others=True)
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def return_expanded(self):
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"""Creates a new StateFilter where type wild cards have been removed
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(except for memberships). The returned filter is a superset of the
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current one, i.e. anything that passes the current filter will pass
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the returned filter.
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This helps the caching as the DictionaryCache knows if it has *all* the
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state, but does not know if it has all of the keys of a particular type,
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which makes wildcard lookups expensive unless we have a complete cache.
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Hence, if we are doing a wildcard lookup, populate the cache fully so
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that we can do an efficient lookup next time.
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Note that since we have two caches, one for membership events and one for
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other events, we can be a bit more clever than simply returning
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`StateFilter.all()` if `has_wildcards()` is True.
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We return a StateFilter where:
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1. the list of membership events to return is the same
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2. if there is a wildcard that matches non-member events we
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return all non-member events
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Returns:
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StateFilter
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"""
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if self.is_full():
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# If we're going to return everything then there's nothing to do
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return self
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if not self.has_wildcards():
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# If there are no wild cards, there's nothing to do
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return self
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if EventTypes.Member in self.types:
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get_all_members = self.types[EventTypes.Member] is None
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else:
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get_all_members = self.include_others
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has_non_member_wildcard = self.include_others or any(
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state_keys is None
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for t, state_keys in iteritems(self.types)
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if t != EventTypes.Member
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)
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if not has_non_member_wildcard:
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# If there are no non-member wild cards we can just return ourselves
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return self
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if get_all_members:
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# We want to return everything.
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return StateFilter.all()
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else:
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# We want to return all non-members, but only particular
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# memberships
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return StateFilter(
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types={EventTypes.Member: self.types[EventTypes.Member]},
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include_others=True,
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)
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def make_sql_filter_clause(self):
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"""Converts the filter to an SQL clause.
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For example:
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f = StateFilter.from_types([("m.room.create", "")])
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clause, args = f.make_sql_filter_clause()
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clause == "(type = ? AND state_key = ?)"
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args == ['m.room.create', '']
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Returns:
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tuple[str, list]: The SQL string (may be empty) and arguments. An
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empty SQL string is returned when the filter matches everything
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(i.e. is "full").
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"""
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where_clause = ""
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where_args = []
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if self.is_full():
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return where_clause, where_args
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if not self.include_others and not self.types:
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# i.e. this is an empty filter, so we need to return a clause that
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# will match nothing
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return "1 = 2", []
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# First we build up a lost of clauses for each type/state_key combo
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clauses = []
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for etype, state_keys in iteritems(self.types):
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if state_keys is None:
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clauses.append("(type = ?)")
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where_args.append(etype)
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continue
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for state_key in state_keys:
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clauses.append("(type = ? AND state_key = ?)")
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where_args.extend((etype, state_key))
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# This will match anything that appears in `self.types`
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where_clause = " OR ".join(clauses)
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# If we want to include stuff that's not in the types dict then we add
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# a `OR type NOT IN (...)` clause to the end.
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if self.include_others:
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if where_clause:
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where_clause += " OR "
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where_clause += "type NOT IN (%s)" % (",".join(["?"] * len(self.types)),)
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where_args.extend(self.types)
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return where_clause, where_args
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def max_entries_returned(self):
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"""Returns the maximum number of entries this filter will return if
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known, otherwise returns None.
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For example a simple state filter asking for `("m.room.create", "")`
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will return 1, whereas the default state filter will return None.
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This is used to bail out early if the right number of entries have been
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fetched.
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"""
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if self.has_wildcards():
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return None
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return len(self.concrete_types())
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def filter_state(self, state_dict):
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"""Returns the state filtered with by this StateFilter
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Args:
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state (dict[tuple[str, str], Any]): The state map to filter
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Returns:
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dict[tuple[str, str], Any]: The filtered state map
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"""
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if self.is_full():
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return dict(state_dict)
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filtered_state = {}
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for k, v in iteritems(state_dict):
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typ, state_key = k
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if typ in self.types:
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state_keys = self.types[typ]
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if state_keys is None or state_key in state_keys:
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filtered_state[k] = v
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elif self.include_others:
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filtered_state[k] = v
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return filtered_state
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def is_full(self):
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"""Whether this filter fetches everything or not
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Returns:
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bool
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"""
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return self.include_others and not self.types
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def has_wildcards(self):
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"""Whether the filter includes wildcards or is attempting to fetch
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specific state.
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Returns:
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bool
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"""
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return self.include_others or any(
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state_keys is None for state_keys in itervalues(self.types)
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)
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def concrete_types(self):
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"""Returns a list of concrete type/state_keys (i.e. not None) that
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will be fetched. This will be a complete list if `has_wildcards`
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returns False, but otherwise will be a subset (or even empty).
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Returns:
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list[tuple[str,str]]
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"""
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return [
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(t, s)
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for t, state_keys in iteritems(self.types)
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if state_keys is not None
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for s in state_keys
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]
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def get_member_split(self):
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"""Return the filter split into two: one which assumes it's exclusively
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matching against member state, and one which assumes it's matching
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against non member state.
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This is useful due to the returned filters giving correct results for
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`is_full()`, `has_wildcards()`, etc, when operating against maps that
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either exclusively contain member events or only contain non-member
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events. (Which is the case when dealing with the member vs non-member
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state caches).
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Returns:
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tuple[StateFilter, StateFilter]: The member and non member filters
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"""
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if EventTypes.Member in self.types:
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state_keys = self.types[EventTypes.Member]
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if state_keys is None:
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member_filter = StateFilter.all()
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else:
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member_filter = StateFilter({EventTypes.Member: state_keys})
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elif self.include_others:
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member_filter = StateFilter.all()
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else:
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member_filter = StateFilter.none()
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non_member_filter = StateFilter(
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types={k: v for k, v in iteritems(self.types) if k != EventTypes.Member},
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include_others=self.include_others,
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)
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return member_filter, non_member_filter
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