Move storage classes into a main "data store".

This is in preparation for having multiple data stores that offer
different functionality, e.g. splitting out state or event storage.

1 files changed, 0 insertions, 1119 deletions

diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index ff63487823..8c4a83a840 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -17,26 +17,6 @@
 import logging
 from collections import namedtuple
 
-from six import iteritems, itervalues
-
-from canonicaljson import json
-
-from twisted.internet import defer
-
-from synapse.api.constants import EventTypes, Membership
-from synapse.metrics import LaterGauge
-from synapse.metrics.background_process_metrics import run_as_background_process
-from synapse.storage._base import LoggingTransaction, make_in_list_sql_clause
-from synapse.storage.background_updates import BackgroundUpdateStore
-from synapse.storage.engines import Sqlite3Engine
-from synapse.storage.events_worker import EventsWorkerStore
-from synapse.types import get_domain_from_id
-from synapse.util.async_helpers import Linearizer
-from synapse.util.caches import intern_string
-from synapse.util.caches.descriptors import cached, cachedInlineCallbacks, cachedList
-from synapse.util.metrics import Measure
-from synapse.util.stringutils import to_ascii
-
 logger = logging.getLogger(__name__)
 
 
@@ -57,1102 +37,3 @@ ProfileInfo = namedtuple("ProfileInfo", ("avatar_url", "display_name"))
 # a given membership type, suitable for use in calculating heroes for a room.
 # "count" points to the total numberr of users of a given membership type.
 MemberSummary = namedtuple("MemberSummary", ("members", "count"))
-
-_MEMBERSHIP_PROFILE_UPDATE_NAME = "room_membership_profile_update"
-_CURRENT_STATE_MEMBERSHIP_UPDATE_NAME = "current_state_events_membership"
-
-
-class RoomMemberWorkerStore(EventsWorkerStore):
-    def __init__(self, db_conn, hs):
-        super(RoomMemberWorkerStore, self).__init__(db_conn, hs)
-
-        # Is the current_state_events.membership up to date? Or is the
-        # background update still running?
-        self._current_state_events_membership_up_to_date = False
-
-        txn = LoggingTransaction(
-            db_conn.cursor(),
-            name="_check_safe_current_state_events_membership_updated",
-            database_engine=self.database_engine,
-        )
-        self._check_safe_current_state_events_membership_updated_txn(txn)
-        txn.close()
-
-        if self.hs.config.metrics_flags.known_servers:
-            self._known_servers_count = 1
-            self.hs.get_clock().looping_call(
-                run_as_background_process,
-                60 * 1000,
-                "_count_known_servers",
-                self._count_known_servers,
-            )
-            self.hs.get_clock().call_later(
-                1000,
-                run_as_background_process,
-                "_count_known_servers",
-                self._count_known_servers,
-            )
-            LaterGauge(
-                "synapse_federation_known_servers",
-                "",
-                [],
-                lambda: self._known_servers_count,
-            )
-
-    @defer.inlineCallbacks
-    def _count_known_servers(self):
-        """
-        Count the servers that this server knows about.
-
-        The statistic is stored on the class for the
-        `synapse_federation_known_servers` LaterGauge to collect.
-        """
-
-        def _transact(txn):
-            if isinstance(self.database_engine, Sqlite3Engine):
-                query = """
-                    SELECT COUNT(DISTINCT substr(out.user_id, pos+1))
-                    FROM (
-                        SELECT rm.user_id as user_id, instr(rm.user_id, ':')
-                            AS pos FROM room_memberships as rm
-                        INNER JOIN current_state_events as c ON rm.event_id = c.event_id
-                        WHERE c.type = 'm.room.member'
-                    ) as out
-                """
-            else:
-                query = """
-                    SELECT COUNT(DISTINCT split_part(state_key, ':', 2))
-                    FROM current_state_events
-                    WHERE type = 'm.room.member' AND membership = 'join';
-                """
-            txn.execute(query)
-            return list(txn)[0][0]
-
-        count = yield self.runInteraction("get_known_servers", _transact)
-
-        # We always know about ourselves, even if we have nothing in
-        # room_memberships (for example, the server is new).
-        self._known_servers_count = max([count, 1])
-        return self._known_servers_count
-
-    def _check_safe_current_state_events_membership_updated_txn(self, txn):
-        """Checks if it is safe to assume the new current_state_events
-        membership column is up to date
-        """
-
-        pending_update = self._simple_select_one_txn(
-            txn,
-            table="background_updates",
-            keyvalues={"update_name": _CURRENT_STATE_MEMBERSHIP_UPDATE_NAME},
-            retcols=["update_name"],
-            allow_none=True,
-        )
-
-        self._current_state_events_membership_up_to_date = not pending_update
-
-        # If the update is still running, reschedule to run.
-        if pending_update:
-            self._clock.call_later(
-                15.0,
-                run_as_background_process,
-                "_check_safe_current_state_events_membership_updated",
-                self.runInteraction,
-                "_check_safe_current_state_events_membership_updated",
-                self._check_safe_current_state_events_membership_updated_txn,
-            )
-
-    @cachedInlineCallbacks(max_entries=100000, iterable=True, cache_context=True)
-    def get_hosts_in_room(self, room_id, cache_context):
-        """Returns the set of all hosts currently in the room
-        """
-        user_ids = yield self.get_users_in_room(
-            room_id, on_invalidate=cache_context.invalidate
-        )
-        hosts = frozenset(get_domain_from_id(user_id) for user_id in user_ids)
-        return hosts
-
-    @cached(max_entries=100000, iterable=True)
-    def get_users_in_room(self, room_id):
-        return self.runInteraction(
-            "get_users_in_room", self.get_users_in_room_txn, room_id
-        )
-
-    def get_users_in_room_txn(self, txn, room_id):
-        # If we can assume current_state_events.membership is up to date
-        # then we can avoid a join, which is a Very Good Thing given how
-        # frequently this function gets called.
-        if self._current_state_events_membership_up_to_date:
-            sql = """
-                SELECT state_key FROM current_state_events
-                WHERE type = 'm.room.member' AND room_id = ? AND membership = ?
-            """
-        else:
-            sql = """
-                SELECT state_key FROM room_memberships as m
-                INNER JOIN current_state_events as c
-                ON m.event_id = c.event_id
-                AND m.room_id = c.room_id
-                AND m.user_id = c.state_key
-                WHERE c.type = 'm.room.member' AND c.room_id = ? AND m.membership = ?
-            """
-
-        txn.execute(sql, (room_id, Membership.JOIN))
-        return [to_ascii(r[0]) for r in txn]
-
-    @cached(max_entries=100000)
-    def get_room_summary(self, room_id):
-        """ Get the details of a room roughly suitable for use by the room
-        summary extension to /sync. Useful when lazy loading room members.
-        Args:
-            room_id (str): The room ID to query
-        Returns:
-            Deferred[dict[str, MemberSummary]:
-                dict of membership states, pointing to a MemberSummary named tuple.
-        """
-
-        def _get_room_summary_txn(txn):
-            # first get counts.
-            # We do this all in one transaction to keep the cache small.
-            # FIXME: get rid of this when we have room_stats
-
-            # If we can assume current_state_events.membership is up to date
-            # then we can avoid a join, which is a Very Good Thing given how
-            # frequently this function gets called.
-            if self._current_state_events_membership_up_to_date:
-                # Note, rejected events will have a null membership field, so
-                # we we manually filter them out.
-                sql = """
-                    SELECT count(*), membership FROM current_state_events
-                    WHERE type = 'm.room.member' AND room_id = ?
-                        AND membership IS NOT NULL
-                    GROUP BY membership
-                """
-            else:
-                sql = """
-                    SELECT count(*), m.membership FROM room_memberships as m
-                    INNER JOIN current_state_events as c
-                    ON m.event_id = c.event_id
-                    AND m.room_id = c.room_id
-                    AND m.user_id = c.state_key
-                    WHERE c.type = 'm.room.member' AND c.room_id = ?
-                    GROUP BY m.membership
-                """
-
-            txn.execute(sql, (room_id,))
-            res = {}
-            for count, membership in txn:
-                summary = res.setdefault(to_ascii(membership), MemberSummary([], count))
-
-            # we order by membership and then fairly arbitrarily by event_id so
-            # heroes are consistent
-            if self._current_state_events_membership_up_to_date:
-                # Note, rejected events will have a null membership field, so
-                # we we manually filter them out.
-                sql = """
-                    SELECT state_key, membership, event_id
-                    FROM current_state_events
-                    WHERE type = 'm.room.member' AND room_id = ?
-                        AND membership IS NOT NULL
-                    ORDER BY
-                        CASE membership WHEN ? THEN 1 WHEN ? THEN 2 ELSE 3 END ASC,
-                        event_id ASC
-                    LIMIT ?
-                """
-            else:
-                sql = """
-                    SELECT c.state_key, m.membership, c.event_id
-                    FROM room_memberships as m
-                    INNER JOIN current_state_events as c USING (room_id, event_id)
-                    WHERE c.type = 'm.room.member' AND c.room_id = ?
-                    ORDER BY
-                        CASE m.membership WHEN ? THEN 1 WHEN ? THEN 2 ELSE 3 END ASC,
-                        c.event_id ASC
-                    LIMIT ?
-                """
-
-            # 6 is 5 (number of heroes) plus 1, in case one of them is the calling user.
-            txn.execute(sql, (room_id, Membership.JOIN, Membership.INVITE, 6))
-            for user_id, membership, event_id in txn:
-                summary = res[to_ascii(membership)]
-                # we will always have a summary for this membership type at this
-                # point given the summary currently contains the counts.
-                members = summary.members
-                members.append((to_ascii(user_id), to_ascii(event_id)))
-
-            return res
-
-        return self.runInteraction("get_room_summary", _get_room_summary_txn)
-
-    def _get_user_counts_in_room_txn(self, txn, room_id):
-        """
-        Get the user count in a room by membership.
-
-        Args:
-            room_id (str)
-            membership (Membership)
-
-        Returns:
-            Deferred[int]
-        """
-        sql = """
-        SELECT m.membership, count(*) FROM room_memberships as m
-            INNER JOIN current_state_events as c USING(event_id)
-            WHERE c.type = 'm.room.member' AND c.room_id = ?
-            GROUP BY m.membership
-        """
-
-        txn.execute(sql, (room_id,))
-        return {row[0]: row[1] for row in txn}
-
-    @cached()
-    def get_invited_rooms_for_user(self, user_id):
-        """ Get all the rooms the user is invited to
-        Args:
-            user_id (str): The user ID.
-        Returns:
-            A deferred list of RoomsForUser.
-        """
-
-        return self.get_rooms_for_user_where_membership_is(user_id, [Membership.INVITE])
-
-    @defer.inlineCallbacks
-    def get_invite_for_user_in_room(self, user_id, room_id):
-        """Gets the invite for the given user and room
-
-        Args:
-            user_id (str)
-            room_id (str)
-
-        Returns:
-            Deferred: Resolves to either a RoomsForUser or None if no invite was
-                found.
-        """
-        invites = yield self.get_invited_rooms_for_user(user_id)
-        for invite in invites:
-            if invite.room_id == room_id:
-                return invite
-        return None
-
-    @defer.inlineCallbacks
-    def get_rooms_for_user_where_membership_is(self, user_id, membership_list):
-        """ Get all the rooms for this user where the membership for this user
-        matches one in the membership list.
-
-        Filters out forgotten rooms.
-
-        Args:
-            user_id (str): The user ID.
-            membership_list (list): A list of synapse.api.constants.Membership
-            values which the user must be in.
-
-        Returns:
-            Deferred[list[RoomsForUser]]
-        """
-        if not membership_list:
-            return defer.succeed(None)
-
-        rooms = yield self.runInteraction(
-            "get_rooms_for_user_where_membership_is",
-            self._get_rooms_for_user_where_membership_is_txn,
-            user_id,
-            membership_list,
-        )
-
-        # Now we filter out forgotten rooms
-        forgotten_rooms = yield self.get_forgotten_rooms_for_user(user_id)
-        return [room for room in rooms if room.room_id not in forgotten_rooms]
-
-    def _get_rooms_for_user_where_membership_is_txn(
-        self, txn, user_id, membership_list
-    ):
-
-        do_invite = Membership.INVITE in membership_list
-        membership_list = [m for m in membership_list if m != Membership.INVITE]
-
-        results = []
-        if membership_list:
-            if self._current_state_events_membership_up_to_date:
-                clause, args = make_in_list_sql_clause(
-                    self.database_engine, "c.membership", membership_list
-                )
-                sql = """
-                    SELECT room_id, e.sender, c.membership, event_id, e.stream_ordering
-                    FROM current_state_events AS c
-                    INNER JOIN events AS e USING (room_id, event_id)
-                    WHERE
-                        c.type = 'm.room.member'
-                        AND state_key = ?
-                        AND %s
-                """ % (
-                    clause,
-                )
-            else:
-                clause, args = make_in_list_sql_clause(
-                    self.database_engine, "m.membership", membership_list
-                )
-                sql = """
-                    SELECT room_id, e.sender, m.membership, event_id, e.stream_ordering
-                    FROM current_state_events AS c
-                    INNER JOIN room_memberships AS m USING (room_id, event_id)
-                    INNER JOIN events AS e USING (room_id, event_id)
-                    WHERE
-                        c.type = 'm.room.member'
-                        AND state_key = ?
-                        AND %s
-                """ % (
-                    clause,
-                )
-
-            txn.execute(sql, (user_id, *args))
-            results = [RoomsForUser(**r) for r in self.cursor_to_dict(txn)]
-
-        if do_invite:
-            sql = (
-                "SELECT i.room_id, inviter, i.event_id, e.stream_ordering"
-                " FROM local_invites as i"
-                " INNER JOIN events as e USING (event_id)"
-                " WHERE invitee = ? AND locally_rejected is NULL"
-                " AND replaced_by is NULL"
-            )
-
-            txn.execute(sql, (user_id,))
-            results.extend(
-                RoomsForUser(
-                    room_id=r["room_id"],
-                    sender=r["inviter"],
-                    event_id=r["event_id"],
-                    stream_ordering=r["stream_ordering"],
-                    membership=Membership.INVITE,
-                )
-                for r in self.cursor_to_dict(txn)
-            )
-
-        return results
-
-    @cachedInlineCallbacks(max_entries=500000, iterable=True)
-    def get_rooms_for_user_with_stream_ordering(self, user_id):
-        """Returns a set of room_ids the user is currently joined to
-
-        Args:
-            user_id (str)
-
-        Returns:
-            Deferred[frozenset[GetRoomsForUserWithStreamOrdering]]: Returns
-            the rooms the user is in currently, along with the stream ordering
-            of the most recent join for that user and room.
-        """
-        rooms = yield self.get_rooms_for_user_where_membership_is(
-            user_id, membership_list=[Membership.JOIN]
-        )
-        return frozenset(
-            GetRoomsForUserWithStreamOrdering(r.room_id, r.stream_ordering)
-            for r in rooms
-        )
-
-    @defer.inlineCallbacks
-    def get_rooms_for_user(self, user_id, on_invalidate=None):
-        """Returns a set of room_ids the user is currently joined to
-        """
-        rooms = yield self.get_rooms_for_user_with_stream_ordering(
-            user_id, on_invalidate=on_invalidate
-        )
-        return frozenset(r.room_id for r in rooms)
-
-    @cachedInlineCallbacks(max_entries=500000, cache_context=True, iterable=True)
-    def get_users_who_share_room_with_user(self, user_id, cache_context):
-        """Returns the set of users who share a room with `user_id`
-        """
-        room_ids = yield self.get_rooms_for_user(
-            user_id, on_invalidate=cache_context.invalidate
-        )
-
-        user_who_share_room = set()
-        for room_id in room_ids:
-            user_ids = yield self.get_users_in_room(
-                room_id, on_invalidate=cache_context.invalidate
-            )
-            user_who_share_room.update(user_ids)
-
-        return user_who_share_room
-
-    @defer.inlineCallbacks
-    def get_joined_users_from_context(self, event, context):
-        state_group = context.state_group
-        if not state_group:
-            # If state_group is None it means it has yet to be assigned a
-            # state group, i.e. we need to make sure that calls with a state_group
-            # of None don't hit previous cached calls with a None state_group.
-            # To do this we set the state_group to a new object as object() != object()
-            state_group = object()
-
-        current_state_ids = yield context.get_current_state_ids(self)
-        result = yield self._get_joined_users_from_context(
-            event.room_id, state_group, current_state_ids, event=event, context=context
-        )
-        return result
-
-    @defer.inlineCallbacks
-    def get_joined_users_from_state(self, room_id, state_entry):
-        state_group = state_entry.state_group
-        if not state_group:
-            # If state_group is None it means it has yet to be assigned a
-            # state group, i.e. we need to make sure that calls with a state_group
-            # of None don't hit previous cached calls with a None state_group.
-            # To do this we set the state_group to a new object as object() != object()
-            state_group = object()
-
-        with Measure(self._clock, "get_joined_users_from_state"):
-            return (
-                yield self._get_joined_users_from_context(
-                    room_id, state_group, state_entry.state, context=state_entry
-                )
-            )
-
-    @cachedInlineCallbacks(
-        num_args=2, cache_context=True, iterable=True, max_entries=100000
-    )
-    def _get_joined_users_from_context(
-        self,
-        room_id,
-        state_group,
-        current_state_ids,
-        cache_context,
-        event=None,
-        context=None,
-    ):
-        # We don't use `state_group`, it's there so that we can cache based
-        # on it. However, it's important that it's never None, since two current_states
-        # with a state_group of None are likely to be different.
-        # See bulk_get_push_rules_for_room for how we work around this.
-        assert state_group is not None
-
-        users_in_room = {}
-        member_event_ids = [
-            e_id
-            for key, e_id in iteritems(current_state_ids)
-            if key[0] == EventTypes.Member
-        ]
-
-        if context is not None:
-            # If we have a context with a delta from a previous state group,
-            # check if we also have the result from the previous group in cache.
-            # If we do then we can reuse that result and simply update it with
-            # any membership changes in `delta_ids`
-            if context.prev_group and context.delta_ids:
-                prev_res = self._get_joined_users_from_context.cache.get(
-                    (room_id, context.prev_group), None
-                )
-                if prev_res and isinstance(prev_res, dict):
-                    users_in_room = dict(prev_res)
-                    member_event_ids = [
-                        e_id
-                        for key, e_id in iteritems(context.delta_ids)
-                        if key[0] == EventTypes.Member
-                    ]
-                    for etype, state_key in context.delta_ids:
-                        users_in_room.pop(state_key, None)
-
-        # We check if we have any of the member event ids in the event cache
-        # before we ask the DB
-
-        # We don't update the event cache hit ratio as it completely throws off
-        # the hit ratio counts. After all, we don't populate the cache if we
-        # miss it here
-        event_map = self._get_events_from_cache(
-            member_event_ids, allow_rejected=False, update_metrics=False
-        )
-
-        missing_member_event_ids = []
-        for event_id in member_event_ids:
-            ev_entry = event_map.get(event_id)
-            if ev_entry:
-                if ev_entry.event.membership == Membership.JOIN:
-                    users_in_room[to_ascii(ev_entry.event.state_key)] = ProfileInfo(
-                        display_name=to_ascii(
-                            ev_entry.event.content.get("displayname", None)
-                        ),
-                        avatar_url=to_ascii(
-                            ev_entry.event.content.get("avatar_url", None)
-                        ),
-                    )
-            else:
-                missing_member_event_ids.append(event_id)
-
-        if missing_member_event_ids:
-            event_to_memberships = yield self._get_joined_profiles_from_event_ids(
-                missing_member_event_ids
-            )
-            users_in_room.update((row for row in event_to_memberships.values() if row))
-
-        if event is not None and event.type == EventTypes.Member:
-            if event.membership == Membership.JOIN:
-                if event.event_id in member_event_ids:
-                    users_in_room[to_ascii(event.state_key)] = ProfileInfo(
-                        display_name=to_ascii(event.content.get("displayname", None)),
-                        avatar_url=to_ascii(event.content.get("avatar_url", None)),
-                    )
-
-        return users_in_room
-
-    @cached(max_entries=10000)
-    def _get_joined_profile_from_event_id(self, event_id):
-        raise NotImplementedError()
-
-    @cachedList(
-        cached_method_name="_get_joined_profile_from_event_id",
-        list_name="event_ids",
-        inlineCallbacks=True,
-    )
-    def _get_joined_profiles_from_event_ids(self, event_ids):
-        """For given set of member event_ids check if they point to a join
-        event and if so return the associated user and profile info.
-
-        Args:
-            event_ids (Iterable[str]): The member event IDs to lookup
-
-        Returns:
-            Deferred[dict[str, Tuple[str, ProfileInfo]|None]]: Map from event ID
-            to `user_id` and ProfileInfo (or None if not join event).
-        """
-
-        rows = yield self._simple_select_many_batch(
-            table="room_memberships",
-            column="event_id",
-            iterable=event_ids,
-            retcols=("user_id", "display_name", "avatar_url", "event_id"),
-            keyvalues={"membership": Membership.JOIN},
-            batch_size=500,
-            desc="_get_membership_from_event_ids",
-        )
-
-        return {
-            row["event_id"]: (
-                row["user_id"],
-                ProfileInfo(
-                    avatar_url=row["avatar_url"], display_name=row["display_name"]
-                ),
-            )
-            for row in rows
-        }
-
-    @cachedInlineCallbacks(max_entries=10000)
-    def is_host_joined(self, room_id, host):
-        if "%" in host or "_" in host:
-            raise Exception("Invalid host name")
-
-        sql = """
-            SELECT state_key FROM current_state_events AS c
-            INNER JOIN room_memberships AS m USING (event_id)
-            WHERE m.membership = 'join'
-                AND type = 'm.room.member'
-                AND c.room_id = ?
-                AND state_key LIKE ?
-            LIMIT 1
-        """
-
-        # We do need to be careful to ensure that host doesn't have any wild cards
-        # in it, but we checked above for known ones and we'll check below that
-        # the returned user actually has the correct domain.
-        like_clause = "%:" + host
-
-        rows = yield self._execute("is_host_joined", None, sql, room_id, like_clause)
-
-        if not rows:
-            return False
-
-        user_id = rows[0][0]
-        if get_domain_from_id(user_id) != host:
-            # This can only happen if the host name has something funky in it
-            raise Exception("Invalid host name")
-
-        return True
-
-    @cachedInlineCallbacks()
-    def was_host_joined(self, room_id, host):
-        """Check whether the server is or ever was in the room.
-
-        Args:
-            room_id (str)
-            host (str)
-
-        Returns:
-            Deferred: Resolves to True if the host is/was in the room, otherwise
-            False.
-        """
-        if "%" in host or "_" in host:
-            raise Exception("Invalid host name")
-
-        sql = """
-            SELECT user_id FROM room_memberships
-            WHERE room_id = ?
-                AND user_id LIKE ?
-                AND membership = 'join'
-            LIMIT 1
-        """
-
-        # We do need to be careful to ensure that host doesn't have any wild cards
-        # in it, but we checked above for known ones and we'll check below that
-        # the returned user actually has the correct domain.
-        like_clause = "%:" + host
-
-        rows = yield self._execute("was_host_joined", None, sql, room_id, like_clause)
-
-        if not rows:
-            return False
-
-        user_id = rows[0][0]
-        if get_domain_from_id(user_id) != host:
-            # This can only happen if the host name has something funky in it
-            raise Exception("Invalid host name")
-
-        return True
-
-    @defer.inlineCallbacks
-    def get_joined_hosts(self, room_id, state_entry):
-        state_group = state_entry.state_group
-        if not state_group:
-            # If state_group is None it means it has yet to be assigned a
-            # state group, i.e. we need to make sure that calls with a state_group
-            # of None don't hit previous cached calls with a None state_group.
-            # To do this we set the state_group to a new object as object() != object()
-            state_group = object()
-
-        with Measure(self._clock, "get_joined_hosts"):
-            return (
-                yield self._get_joined_hosts(
-                    room_id, state_group, state_entry.state, state_entry=state_entry
-                )
-            )
-
-    @cachedInlineCallbacks(num_args=2, max_entries=10000, iterable=True)
-    # @defer.inlineCallbacks
-    def _get_joined_hosts(self, room_id, state_group, current_state_ids, state_entry):
-        # We don't use `state_group`, its there so that we can cache based
-        # on it. However, its important that its never None, since two current_state's
-        # with a state_group of None are likely to be different.
-        # See bulk_get_push_rules_for_room for how we work around this.
-        assert state_group is not None
-
-        cache = self._get_joined_hosts_cache(room_id)
-        joined_hosts = yield cache.get_destinations(state_entry)
-
-        return joined_hosts
-
-    @cached(max_entries=10000)
-    def _get_joined_hosts_cache(self, room_id):
-        return _JoinedHostsCache(self, room_id)
-
-    @cachedInlineCallbacks(num_args=2)
-    def did_forget(self, user_id, room_id):
-        """Returns whether user_id has elected to discard history for room_id.
-
-        Returns False if they have since re-joined."""
-
-        def f(txn):
-            sql = (
-                "SELECT"
-                "  COUNT(*)"
-                " FROM"
-                "  room_memberships"
-                " WHERE"
-                "  user_id = ?"
-                " AND"
-                "  room_id = ?"
-                " AND"
-                "  forgotten = 0"
-            )
-            txn.execute(sql, (user_id, room_id))
-            rows = txn.fetchall()
-            return rows[0][0]
-
-        count = yield self.runInteraction("did_forget_membership", f)
-        return count == 0
-
-    @cached()
-    def get_forgotten_rooms_for_user(self, user_id):
-        """Gets all rooms the user has forgotten.
-
-        Args:
-            user_id (str)
-
-        Returns:
-            Deferred[set[str]]
-        """
-
-        def _get_forgotten_rooms_for_user_txn(txn):
-            # This is a slightly convoluted query that first looks up all rooms
-            # that the user has forgotten in the past, then rechecks that list
-            # to see if any have subsequently been updated. This is done so that
-            # we can use a partial index on `forgotten = 1` on the assumption
-            # that few users will actually forget many rooms.
-            #
-            # Note that a room is considered "forgotten" if *all* membership
-            # events for that user and room have the forgotten field set (as
-            # when a user forgets a room we update all rows for that user and
-            # room, not just the current one).
-            sql = """
-                SELECT room_id, (
-                    SELECT count(*) FROM room_memberships
-                    WHERE room_id = m.room_id AND user_id = m.user_id AND forgotten = 0
-                ) AS count
-                FROM room_memberships AS m
-                WHERE user_id = ? AND forgotten = 1
-                GROUP BY room_id, user_id;
-            """
-            txn.execute(sql, (user_id,))
-            return set(row[0] for row in txn if row[1] == 0)
-
-        return self.runInteraction(
-            "get_forgotten_rooms_for_user", _get_forgotten_rooms_for_user_txn
-        )
-
-    @defer.inlineCallbacks
-    def get_rooms_user_has_been_in(self, user_id):
-        """Get all rooms that the user has ever been in.
-
-        Args:
-            user_id (str)
-
-        Returns:
-            Deferred[set[str]]: Set of room IDs.
-        """
-
-        room_ids = yield self._simple_select_onecol(
-            table="room_memberships",
-            keyvalues={"membership": Membership.JOIN, "user_id": user_id},
-            retcol="room_id",
-            desc="get_rooms_user_has_been_in",
-        )
-
-        return set(room_ids)
-
-
-class RoomMemberBackgroundUpdateStore(BackgroundUpdateStore):
-    def __init__(self, db_conn, hs):
-        super(RoomMemberBackgroundUpdateStore, self).__init__(db_conn, hs)
-        self.register_background_update_handler(
-            _MEMBERSHIP_PROFILE_UPDATE_NAME, self._background_add_membership_profile
-        )
-        self.register_background_update_handler(
-            _CURRENT_STATE_MEMBERSHIP_UPDATE_NAME,
-            self._background_current_state_membership,
-        )
-        self.register_background_index_update(
-            "room_membership_forgotten_idx",
-            index_name="room_memberships_user_room_forgotten",
-            table="room_memberships",
-            columns=["user_id", "room_id"],
-            where_clause="forgotten = 1",
-        )
-
-    @defer.inlineCallbacks
-    def _background_add_membership_profile(self, progress, batch_size):
-        target_min_stream_id = progress.get(
-            "target_min_stream_id_inclusive", self._min_stream_order_on_start
-        )
-        max_stream_id = progress.get(
-            "max_stream_id_exclusive", self._stream_order_on_start + 1
-        )
-
-        INSERT_CLUMP_SIZE = 1000
-
-        def add_membership_profile_txn(txn):
-            sql = """
-                SELECT stream_ordering, event_id, events.room_id, event_json.json
-                FROM events
-                INNER JOIN event_json USING (event_id)
-                INNER JOIN room_memberships USING (event_id)
-                WHERE ? <= stream_ordering AND stream_ordering < ?
-                AND type = 'm.room.member'
-                ORDER BY stream_ordering DESC
-                LIMIT ?
-            """
-
-            txn.execute(sql, (target_min_stream_id, max_stream_id, batch_size))
-
-            rows = self.cursor_to_dict(txn)
-            if not rows:
-                return 0
-
-            min_stream_id = rows[-1]["stream_ordering"]
-
-            to_update = []
-            for row in rows:
-                event_id = row["event_id"]
-                room_id = row["room_id"]
-                try:
-                    event_json = json.loads(row["json"])
-                    content = event_json["content"]
-                except Exception:
-                    continue
-
-                display_name = content.get("displayname", None)
-                avatar_url = content.get("avatar_url", None)
-
-                if display_name or avatar_url:
-                    to_update.append((display_name, avatar_url, event_id, room_id))
-
-            to_update_sql = """
-                UPDATE room_memberships SET display_name = ?, avatar_url = ?
-                WHERE event_id = ? AND room_id = ?
-            """
-            for index in range(0, len(to_update), INSERT_CLUMP_SIZE):
-                clump = to_update[index : index + INSERT_CLUMP_SIZE]
-                txn.executemany(to_update_sql, clump)
-
-            progress = {
-                "target_min_stream_id_inclusive": target_min_stream_id,
-                "max_stream_id_exclusive": min_stream_id,
-            }
-
-            self._background_update_progress_txn(
-                txn, _MEMBERSHIP_PROFILE_UPDATE_NAME, progress
-            )
-
-            return len(rows)
-
-        result = yield self.runInteraction(
-            _MEMBERSHIP_PROFILE_UPDATE_NAME, add_membership_profile_txn
-        )
-
-        if not result:
-            yield self._end_background_update(_MEMBERSHIP_PROFILE_UPDATE_NAME)
-
-        return result
-
-    @defer.inlineCallbacks
-    def _background_current_state_membership(self, progress, batch_size):
-        """Update the new membership column on current_state_events.
-
-        This works by iterating over all rooms in alphebetical order.
-        """
-
-        def _background_current_state_membership_txn(txn, last_processed_room):
-            processed = 0
-            while processed < batch_size:
-                txn.execute(
-                    """
-                        SELECT MIN(room_id) FROM current_state_events WHERE room_id > ?
-                    """,
-                    (last_processed_room,),
-                )
-                row = txn.fetchone()
-                if not row or not row[0]:
-                    return processed, True
-
-                next_room, = row
-
-                sql = """
-                    UPDATE current_state_events
-                    SET membership = (
-                        SELECT membership FROM room_memberships
-                        WHERE event_id = current_state_events.event_id
-                    )
-                    WHERE room_id = ?
-                """
-                txn.execute(sql, (next_room,))
-                processed += txn.rowcount
-
-                last_processed_room = next_room
-
-            self._background_update_progress_txn(
-                txn,
-                _CURRENT_STATE_MEMBERSHIP_UPDATE_NAME,
-                {"last_processed_room": last_processed_room},
-            )
-
-            return processed, False
-
-        # If we haven't got a last processed room then just use the empty
-        # string, which will compare before all room IDs correctly.
-        last_processed_room = progress.get("last_processed_room", "")
-
-        row_count, finished = yield self.runInteraction(
-            "_background_current_state_membership_update",
-            _background_current_state_membership_txn,
-            last_processed_room,
-        )
-
-        if finished:
-            yield self._end_background_update(_CURRENT_STATE_MEMBERSHIP_UPDATE_NAME)
-
-        return row_count
-
-
-class RoomMemberStore(RoomMemberWorkerStore, RoomMemberBackgroundUpdateStore):
-    def __init__(self, db_conn, hs):
-        super(RoomMemberStore, self).__init__(db_conn, hs)
-
-    def _store_room_members_txn(self, txn, events, backfilled):
-        """Store a room member in the database.
-        """
-        self._simple_insert_many_txn(
-            txn,
-            table="room_memberships",
-            values=[
-                {
-                    "event_id": event.event_id,
-                    "user_id": event.state_key,
-                    "sender": event.user_id,
-                    "room_id": event.room_id,
-                    "membership": event.membership,
-                    "display_name": event.content.get("displayname", None),
-                    "avatar_url": event.content.get("avatar_url", None),
-                }
-                for event in events
-            ],
-        )
-
-        for event in events:
-            txn.call_after(
-                self._membership_stream_cache.entity_has_changed,
-                event.state_key,
-                event.internal_metadata.stream_ordering,
-            )
-            txn.call_after(
-                self.get_invited_rooms_for_user.invalidate, (event.state_key,)
-            )
-
-            # We update the local_invites table only if the event is "current",
-            # i.e., its something that has just happened. If the event is an
-            # outlier it is only current if its an "out of band membership",
-            # like a remote invite or a rejection of a remote invite.
-            is_new_state = not backfilled and (
-                not event.internal_metadata.is_outlier()
-                or event.internal_metadata.is_out_of_band_membership()
-            )
-            is_mine = self.hs.is_mine_id(event.state_key)
-            if is_new_state and is_mine:
-                if event.membership == Membership.INVITE:
-                    self._simple_insert_txn(
-                        txn,
-                        table="local_invites",
-                        values={
-                            "event_id": event.event_id,
-                            "invitee": event.state_key,
-                            "inviter": event.sender,
-                            "room_id": event.room_id,
-                            "stream_id": event.internal_metadata.stream_ordering,
-                        },
-                    )
-                else:
-                    sql = (
-                        "UPDATE local_invites SET stream_id = ?, replaced_by = ? WHERE"
-                        " room_id = ? AND invitee = ? AND locally_rejected is NULL"
-                        " AND replaced_by is NULL"
-                    )
-
-                    txn.execute(
-                        sql,
-                        (
-                            event.internal_metadata.stream_ordering,
-                            event.event_id,
-                            event.room_id,
-                            event.state_key,
-                        ),
-                    )
-
-    @defer.inlineCallbacks
-    def locally_reject_invite(self, user_id, room_id):
-        sql = (
-            "UPDATE local_invites SET stream_id = ?, locally_rejected = ? WHERE"
-            " room_id = ? AND invitee = ? AND locally_rejected is NULL"
-            " AND replaced_by is NULL"
-        )
-
-        def f(txn, stream_ordering):
-            txn.execute(sql, (stream_ordering, True, room_id, user_id))
-
-        with self._stream_id_gen.get_next() as stream_ordering:
-            yield self.runInteraction("locally_reject_invite", f, stream_ordering)
-
-    def forget(self, user_id, room_id):
-        """Indicate that user_id wishes to discard history for room_id."""
-
-        def f(txn):
-            sql = (
-                "UPDATE"
-                "  room_memberships"
-                " SET"
-                "  forgotten = 1"
-                " WHERE"
-                "  user_id = ?"
-                " AND"
-                "  room_id = ?"
-            )
-            txn.execute(sql, (user_id, room_id))
-
-            self._invalidate_cache_and_stream(txn, self.did_forget, (user_id, room_id))
-            self._invalidate_cache_and_stream(
-                txn, self.get_forgotten_rooms_for_user, (user_id,)
-            )
-
-        return self.runInteraction("forget_membership", f)
-
-
-class _JoinedHostsCache(object):
-    """Cache for joined hosts in a room that is optimised to handle updates
-    via state deltas.
-    """
-
-    def __init__(self, store, room_id):
-        self.store = store
-        self.room_id = room_id
-
-        self.hosts_to_joined_users = {}
-
-        self.state_group = object()
-
-        self.linearizer = Linearizer("_JoinedHostsCache")
-
-        self._len = 0
-
-    @defer.inlineCallbacks
-    def get_destinations(self, state_entry):
-        """Get set of destinations for a state entry
-
-        Args:
-            state_entry(synapse.state._StateCacheEntry)
-        """
-        if state_entry.state_group == self.state_group:
-            return frozenset(self.hosts_to_joined_users)
-
-        with (yield self.linearizer.queue(())):
-            if state_entry.state_group == self.state_group:
-                pass
-            elif state_entry.prev_group == self.state_group:
-                for (typ, state_key), event_id in iteritems(state_entry.delta_ids):
-                    if typ != EventTypes.Member:
-                        continue
-
-                    host = intern_string(get_domain_from_id(state_key))
-                    user_id = state_key
-                    known_joins = self.hosts_to_joined_users.setdefault(host, set())
-
-                    event = yield self.store.get_event(event_id)
-                    if event.membership == Membership.JOIN:
-                        known_joins.add(user_id)
-                    else:
-                        known_joins.discard(user_id)
-
-                        if not known_joins:
-                            self.hosts_to_joined_users.pop(host, None)
-            else:
-                joined_users = yield self.store.get_joined_users_from_state(
-                    self.room_id, state_entry
-                )
-
-                self.hosts_to_joined_users = {}
-                for user_id in joined_users:
-                    host = intern_string(get_domain_from_id(user_id))
-                    self.hosts_to_joined_users.setdefault(host, set()).add(user_id)
-
-            if state_entry.state_group:
-                self.state_group = state_entry.state_group
-            else:
-                self.state_group = object()
-            self._len = sum(len(v) for v in itervalues(self.hosts_to_joined_users))
-        return frozenset(self.hosts_to_joined_users)
-
-    def __len__(self):
-        return self._len