Rename database classes to make some sense (#8033)

1 files changed, 1139 insertions, 0 deletions

diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
new file mode 100644
index 0000000000..7c5be251bd
--- /dev/null
+++ b/synapse/storage/databases/main/roommember.py
@@ -0,0 +1,1139 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2018 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+from typing import Iterable, List, Set
+
+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,
+    SQLBaseStore,
+    db_to_json,
+    make_in_list_sql_clause,
+)
+from synapse.storage.database import DatabasePool
+from synapse.storage.databases.main.events_worker import EventsWorkerStore
+from synapse.storage.engines import Sqlite3Engine
+from synapse.storage.roommember import (
+    GetRoomsForUserWithStreamOrdering,
+    MemberSummary,
+    ProfileInfo,
+    RoomsForUser,
+)
+from synapse.types import Collection, 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
+
+logger = logging.getLogger(__name__)
+
+
+_MEMBERSHIP_PROFILE_UPDATE_NAME = "room_membership_profile_update"
+_CURRENT_STATE_MEMBERSHIP_UPDATE_NAME = "current_state_events_membership"
+
+
+class RoomMemberWorkerStore(EventsWorkerStore):
+    def __init__(self, database: DatabasePool, db_conn, hs):
+        super(RoomMemberWorkerStore, self).__init__(database, 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.db_pool.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.db_pool.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.db_pool.runInteraction,
+                "_check_safe_current_state_events_membership_updated",
+                self._check_safe_current_state_events_membership_updated_txn,
+            )
+
+    @cached(max_entries=100000, iterable=True)
+    def get_users_in_room(self, room_id):
+        return self.db_pool.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 [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(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[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((user_id, event_id))
+
+            return res
+
+        return self.db_pool.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_local_user(self, user_id):
+        """ Get all the rooms the *local* user is invited to
+
+        Args:
+            user_id (str): The user ID.
+        Returns:
+            A deferred list of RoomsForUser.
+        """
+
+        return self.get_rooms_for_local_user_where_membership_is(
+            user_id, [Membership.INVITE]
+        )
+
+    @defer.inlineCallbacks
+    def get_invite_for_local_user_in_room(self, user_id, room_id):
+        """Gets the invite for the given *local* 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_local_user(user_id)
+        for invite in invites:
+            if invite.room_id == room_id:
+                return invite
+        return None
+
+    @defer.inlineCallbacks
+    def get_rooms_for_local_user_where_membership_is(self, user_id, membership_list):
+        """ Get all the rooms for this *local* 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.db_pool.runInteraction(
+            "get_rooms_for_local_user_where_membership_is",
+            self._get_rooms_for_local_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_local_user_where_membership_is_txn(
+        self, txn, user_id, membership_list
+    ):
+        # Paranoia check.
+        if not self.hs.is_mine_id(user_id):
+            raise Exception(
+                "Cannot call 'get_rooms_for_local_user_where_membership_is' on non-local user %r"
+                % (user_id,),
+            )
+
+        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 local_current_membership AS c
+            INNER JOIN events AS e USING (room_id, event_id)
+            WHERE
+                user_id = ?
+                AND %s
+        """ % (
+            clause,
+        )
+
+        txn.execute(sql, (user_id, *args))
+        results = [RoomsForUser(**r) for r in self.db_pool.cursor_to_dict(txn)]
+
+        return results
+
+    @cached(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.
+
+        If a remote user only returns rooms this server is currently
+        participating in.
+
+        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.
+        """
+        return self.db_pool.runInteraction(
+            "get_rooms_for_user_with_stream_ordering",
+            self._get_rooms_for_user_with_stream_ordering_txn,
+            user_id,
+        )
+
+    def _get_rooms_for_user_with_stream_ordering_txn(self, txn, user_id):
+        # We use `current_state_events` here and not `local_current_membership`
+        # as a) this gets called with remote users and b) this only gets called
+        # for rooms the server is participating in.
+        if self._current_state_events_membership_up_to_date:
+            sql = """
+                SELECT room_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 c.membership = ?
+            """
+        else:
+            sql = """
+                SELECT room_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 m.membership = ?
+            """
+
+        txn.execute(sql, (user_id, Membership.JOIN))
+        results = frozenset(GetRoomsForUserWithStreamOrdering(*row) for row in txn)
+
+        return results
+
+    async def get_users_server_still_shares_room_with(
+        self, user_ids: Collection[str]
+    ) -> Set[str]:
+        """Given a list of users return the set that the server still share a
+        room with.
+        """
+
+        if not user_ids:
+            return set()
+
+        def _get_users_server_still_shares_room_with_txn(txn):
+            sql = """
+                SELECT state_key FROM current_state_events
+                WHERE
+                    type = 'm.room.member'
+                    AND membership = 'join'
+                    AND %s
+                GROUP BY state_key
+            """
+
+            clause, args = make_in_list_sql_clause(
+                self.database_engine, "state_key", user_ids
+            )
+
+            txn.execute(sql % (clause,), args)
+
+            return {row[0] for row in txn}
+
+        return await self.db_pool.runInteraction(
+            "get_users_server_still_shares_room_with",
+            _get_users_server_still_shares_room_with_txn,
+        )
+
+    @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.
+
+        If a remote user only returns rooms this server is currently
+        participating in.
+        """
+        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 defer.ensureDeferred(context.get_current_state_ids())
+        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 current_state_ids.items()
+            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 context.delta_ids.items()
+                        if key[0] == EventTypes.Member
+                    ]
+                    for etype, state_key in context.delta_ids:
+                        if etype == EventTypes.Member:
+                            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[ev_entry.event.state_key] = ProfileInfo(
+                        display_name=ev_entry.event.content.get("displayname", None),
+                        avatar_url=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[event.state_key] = ProfileInfo(
+                        display_name=event.content.get("displayname", None),
+                        avatar_url=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.db_pool.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.db_pool.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.db_pool.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 = yield 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.db_pool.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 {row[0] for row in txn if row[1] == 0}
+
+        return self.db_pool.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.db_pool.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)
+
+    def get_membership_from_event_ids(
+        self, member_event_ids: Iterable[str]
+    ) -> List[dict]:
+        """Get user_id and membership of a set of event IDs.
+        """
+
+        return self.db_pool.simple_select_many_batch(
+            table="room_memberships",
+            column="event_id",
+            iterable=member_event_ids,
+            retcols=("user_id", "membership", "event_id"),
+            keyvalues={},
+            batch_size=500,
+            desc="get_membership_from_event_ids",
+        )
+
+    async def is_local_host_in_room_ignoring_users(
+        self, room_id: str, ignore_users: Collection[str]
+    ) -> bool:
+        """Check if there are any local users, excluding those in the given
+        list, in the room.
+        """
+
+        clause, args = make_in_list_sql_clause(
+            self.database_engine, "user_id", ignore_users
+        )
+
+        sql = """
+            SELECT 1 FROM local_current_membership
+            WHERE
+                room_id = ? AND membership = ?
+                AND NOT (%s)
+                LIMIT 1
+        """ % (
+            clause,
+        )
+
+        def _is_local_host_in_room_ignoring_users_txn(txn):
+            txn.execute(sql, (room_id, Membership.JOIN, *args))
+
+            return bool(txn.fetchone())
+
+        return await self.db_pool.runInteraction(
+            "is_local_host_in_room_ignoring_users",
+            _is_local_host_in_room_ignoring_users_txn,
+        )
+
+
+class RoomMemberBackgroundUpdateStore(SQLBaseStore):
+    def __init__(self, database: DatabasePool, db_conn, hs):
+        super(RoomMemberBackgroundUpdateStore, self).__init__(database, db_conn, hs)
+        self.db_pool.updates.register_background_update_handler(
+            _MEMBERSHIP_PROFILE_UPDATE_NAME, self._background_add_membership_profile
+        )
+        self.db_pool.updates.register_background_update_handler(
+            _CURRENT_STATE_MEMBERSHIP_UPDATE_NAME,
+            self._background_current_state_membership,
+        )
+        self.db_pool.updates.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.db_pool.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 = db_to_json(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.db_pool.updates._background_update_progress_txn(
+                txn, _MEMBERSHIP_PROFILE_UPDATE_NAME, progress
+            )
+
+            return len(rows)
+
+        result = yield self.db_pool.runInteraction(
+            _MEMBERSHIP_PROFILE_UPDATE_NAME, add_membership_profile_txn
+        )
+
+        if not result:
+            yield self.db_pool.updates._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.db_pool.updates._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.db_pool.runInteraction(
+            "_background_current_state_membership_update",
+            _background_current_state_membership_txn,
+            last_processed_room,
+        )
+
+        if finished:
+            yield self.db_pool.updates._end_background_update(
+                _CURRENT_STATE_MEMBERSHIP_UPDATE_NAME
+            )
+
+        return row_count
+
+
+class RoomMemberStore(RoomMemberWorkerStore, RoomMemberBackgroundUpdateStore):
+    def __init__(self, database: DatabasePool, db_conn, hs):
+        super(RoomMemberStore, self).__init__(database, db_conn, hs)
+
+    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.db_pool.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 state_entry.delta_ids.items():
+                    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 self.hosts_to_joined_users.values())
+        return frozenset(self.hosts_to_joined_users)
+
+    def __len__(self):
+        return self._len