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- # Copyright 2020 The Matrix.org Foundation C.I.C.
- #
- # 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 Any, List, Set, Tuple
-
- from synapse.api.errors import SynapseError
- from synapse.storage.databases.main import CacheInvalidationWorkerStore
- from synapse.storage.databases.main.state import StateGroupWorkerStore
- from synapse.types import RoomStreamToken
-
- logger = logging.getLogger(__name__)
-
-
- class PurgeEventsStore(StateGroupWorkerStore, CacheInvalidationWorkerStore):
- async def purge_history(
- self, room_id: str, token: str, delete_local_events: bool
- ) -> Set[int]:
- """Deletes room history before a certain point.
-
- Note that only a single purge can occur at once, this is guaranteed via
- a higher level (in the PaginationHandler).
-
- Args:
- room_id:
- token: A topological token to delete events before
- delete_local_events:
- if True, we will delete local events as well as remote ones
- (instead of just marking them as outliers and deleting their
- state groups).
-
- Returns:
- The set of state groups that are referenced by deleted events.
- """
-
- parsed_token = await RoomStreamToken.parse(self, token)
-
- return await self.db_pool.runInteraction(
- "purge_history",
- self._purge_history_txn,
- room_id,
- parsed_token,
- delete_local_events,
- )
-
- def _purge_history_txn(
- self, txn, room_id: str, token: RoomStreamToken, delete_local_events: bool
- ) -> Set[int]:
- # Tables that should be pruned:
- # event_auth
- # event_backward_extremities
- # event_edges
- # event_forward_extremities
- # event_json
- # event_push_actions
- # event_reference_hashes
- # event_relations
- # event_search
- # event_to_state_groups
- # events
- # rejections
- # room_depth
- # state_groups
- # state_groups_state
- # destination_rooms
-
- # we will build a temporary table listing the events so that we don't
- # have to keep shovelling the list back and forth across the
- # connection. Annoyingly the python sqlite driver commits the
- # transaction on CREATE, so let's do this first.
- #
- # furthermore, we might already have the table from a previous (failed)
- # purge attempt, so let's drop the table first.
-
- txn.execute("DROP TABLE IF EXISTS events_to_purge")
-
- txn.execute(
- "CREATE TEMPORARY TABLE events_to_purge ("
- " event_id TEXT NOT NULL,"
- " should_delete BOOLEAN NOT NULL"
- ")"
- )
-
- # First ensure that we're not about to delete all the forward extremeties
- txn.execute(
- "SELECT e.event_id, e.depth FROM events as e "
- "INNER JOIN event_forward_extremities as f "
- "ON e.event_id = f.event_id "
- "AND e.room_id = f.room_id "
- "WHERE f.room_id = ?",
- (room_id,),
- )
- rows = txn.fetchall()
- max_depth = max(row[1] for row in rows)
-
- if max_depth < token.topological:
- # We need to ensure we don't delete all the events from the database
- # otherwise we wouldn't be able to send any events (due to not
- # having any backwards extremities)
- raise SynapseError(
- 400, "topological_ordering is greater than forward extremeties"
- )
-
- logger.info("[purge] looking for events to delete")
-
- should_delete_expr = "state_key IS NULL"
- should_delete_params = () # type: Tuple[Any, ...]
- if not delete_local_events:
- should_delete_expr += " AND event_id NOT LIKE ?"
-
- # We include the parameter twice since we use the expression twice
- should_delete_params += ("%:" + self.hs.hostname, "%:" + self.hs.hostname)
-
- should_delete_params += (room_id, token.topological)
-
- # Note that we insert events that are outliers and aren't going to be
- # deleted, as nothing will happen to them.
- txn.execute(
- "INSERT INTO events_to_purge"
- " SELECT event_id, %s"
- " FROM events AS e LEFT JOIN state_events USING (event_id)"
- " WHERE (NOT outlier OR (%s)) AND e.room_id = ? AND topological_ordering < ?"
- % (should_delete_expr, should_delete_expr),
- should_delete_params,
- )
-
- # We create the indices *after* insertion as that's a lot faster.
-
- # create an index on should_delete because later we'll be looking for
- # the should_delete / shouldn't_delete subsets
- txn.execute(
- "CREATE INDEX events_to_purge_should_delete"
- " ON events_to_purge(should_delete)"
- )
-
- # We do joins against events_to_purge for e.g. calculating state
- # groups to purge, etc., so lets make an index.
- txn.execute("CREATE INDEX events_to_purge_id ON events_to_purge(event_id)")
-
- txn.execute("SELECT event_id, should_delete FROM events_to_purge")
- event_rows = txn.fetchall()
- logger.info(
- "[purge] found %i events before cutoff, of which %i can be deleted",
- len(event_rows),
- sum(1 for e in event_rows if e[1]),
- )
-
- logger.info("[purge] Finding new backward extremities")
-
- # We calculate the new entries for the backward extremities by finding
- # events to be purged that are pointed to by events we're not going to
- # purge.
- txn.execute(
- "SELECT DISTINCT e.event_id FROM events_to_purge AS e"
- " INNER JOIN event_edges AS ed ON e.event_id = ed.prev_event_id"
- " LEFT JOIN events_to_purge AS ep2 ON ed.event_id = ep2.event_id"
- " WHERE ep2.event_id IS NULL"
- )
- new_backwards_extrems = txn.fetchall()
-
- logger.info("[purge] replacing backward extremities: %r", new_backwards_extrems)
-
- txn.execute(
- "DELETE FROM event_backward_extremities WHERE room_id = ?", (room_id,)
- )
-
- # Update backward extremeties
- txn.execute_batch(
- "INSERT INTO event_backward_extremities (room_id, event_id)"
- " VALUES (?, ?)",
- [(room_id, event_id) for event_id, in new_backwards_extrems],
- )
-
- logger.info("[purge] finding state groups referenced by deleted events")
-
- # Get all state groups that are referenced by events that are to be
- # deleted.
- txn.execute(
- """
- SELECT DISTINCT state_group FROM events_to_purge
- INNER JOIN event_to_state_groups USING (event_id)
- """
- )
-
- referenced_state_groups = {sg for sg, in txn}
- logger.info(
- "[purge] found %i referenced state groups", len(referenced_state_groups)
- )
-
- logger.info("[purge] removing events from event_to_state_groups")
- txn.execute(
- "DELETE FROM event_to_state_groups "
- "WHERE event_id IN (SELECT event_id from events_to_purge)"
- )
-
- # Delete all remote non-state events
- for table in (
- "events",
- "event_json",
- "event_auth",
- "event_edges",
- "event_forward_extremities",
- "event_reference_hashes",
- "event_relations",
- "event_search",
- "rejections",
- ):
- logger.info("[purge] removing events from %s", table)
-
- txn.execute(
- "DELETE FROM %s WHERE event_id IN ("
- " SELECT event_id FROM events_to_purge WHERE should_delete"
- ")" % (table,)
- )
-
- # event_push_actions lacks an index on event_id, and has one on
- # (room_id, event_id) instead.
- for table in ("event_push_actions",):
- logger.info("[purge] removing events from %s", table)
-
- txn.execute(
- "DELETE FROM %s WHERE room_id = ? AND event_id IN ("
- " SELECT event_id FROM events_to_purge WHERE should_delete"
- ")" % (table,),
- (room_id,),
- )
-
- # Mark all state and own events as outliers
- logger.info("[purge] marking remaining events as outliers")
- txn.execute(
- "UPDATE events SET outlier = ?"
- " WHERE event_id IN ("
- " SELECT event_id FROM events_to_purge "
- " WHERE NOT should_delete"
- ")",
- (True,),
- )
-
- # synapse tries to take out an exclusive lock on room_depth whenever it
- # persists events (because upsert), and once we run this update, we
- # will block that for the rest of our transaction.
- #
- # So, let's stick it at the end so that we don't block event
- # persistence.
- #
- # We do this by calculating the minimum depth of the backwards
- # extremities. However, the events in event_backward_extremities
- # are ones we don't have yet so we need to look at the events that
- # point to it via event_edges table.
- txn.execute(
- """
- SELECT COALESCE(MIN(depth), 0)
- FROM event_backward_extremities AS eb
- INNER JOIN event_edges AS eg ON eg.prev_event_id = eb.event_id
- INNER JOIN events AS e ON e.event_id = eg.event_id
- WHERE eb.room_id = ?
- """,
- (room_id,),
- )
- (min_depth,) = txn.fetchone()
-
- logger.info("[purge] updating room_depth to %d", min_depth)
-
- txn.execute(
- "UPDATE room_depth SET min_depth = ? WHERE room_id = ?",
- (min_depth, room_id),
- )
-
- # finally, drop the temp table. this will commit the txn in sqlite,
- # so make sure to keep this actually last.
- txn.execute("DROP TABLE events_to_purge")
-
- for event_id, should_delete in event_rows:
- self._invalidate_cache_and_stream(
- txn, self._get_state_group_for_event, (event_id,)
- )
-
- # XXX: This is racy, since have_seen_events could be called between the
- # transaction completing and the invalidation running. On the other hand,
- # that's no different to calling `have_seen_events` just before the
- # event is deleted from the database.
- if should_delete:
- self._invalidate_cache_and_stream(
- txn, self.have_seen_event, (room_id, event_id)
- )
-
- logger.info("[purge] done")
-
- return referenced_state_groups
-
- async def purge_room(self, room_id: str) -> List[int]:
- """Deletes all record of a room
-
- Args:
- room_id
-
- Returns:
- The list of state groups to delete.
- """
- return await self.db_pool.runInteraction(
- "purge_room", self._purge_room_txn, room_id
- )
-
- def _purge_room_txn(self, txn, room_id: str) -> List[int]:
- # First we fetch all the state groups that should be deleted, before
- # we delete that information.
- txn.execute(
- """
- SELECT DISTINCT state_group FROM events
- INNER JOIN event_to_state_groups USING(event_id)
- WHERE events.room_id = ?
- """,
- (room_id,),
- )
-
- state_groups = [row[0] for row in txn]
-
- # Get all the auth chains that are referenced by events that are to be
- # deleted.
- txn.execute(
- """
- SELECT chain_id, sequence_number FROM events
- LEFT JOIN event_auth_chains USING (event_id)
- WHERE room_id = ?
- """,
- (room_id,),
- )
- referenced_chain_id_tuples = list(txn)
-
- logger.info("[purge] removing events from event_auth_chain_links")
- txn.executemany(
- """
- DELETE FROM event_auth_chain_links WHERE
- origin_chain_id = ? AND origin_sequence_number = ?
- """,
- referenced_chain_id_tuples,
- )
-
- # Now we delete tables which lack an index on room_id but have one on event_id
- for table in (
- "event_auth",
- "event_edges",
- "event_json",
- "event_push_actions_staging",
- "event_reference_hashes",
- "event_relations",
- "event_to_state_groups",
- "event_auth_chains",
- "event_auth_chain_to_calculate",
- "redactions",
- "rejections",
- "state_events",
- ):
- logger.info("[purge] removing %s from %s", room_id, table)
-
- txn.execute(
- """
- DELETE FROM %s WHERE event_id IN (
- SELECT event_id FROM events WHERE room_id=?
- )
- """
- % (table,),
- (room_id,),
- )
-
- # and finally, the tables with an index on room_id (or no useful index)
- for table in (
- "current_state_events",
- "destination_rooms",
- "event_backward_extremities",
- "event_forward_extremities",
- "event_push_actions",
- "event_search",
- "events",
- "group_rooms",
- "public_room_list_stream",
- "receipts_graph",
- "receipts_linearized",
- "room_aliases",
- "room_depth",
- "room_memberships",
- "room_stats_state",
- "room_stats_current",
- "room_stats_earliest_token",
- "rooms",
- "stream_ordering_to_exterm",
- "users_in_public_rooms",
- "users_who_share_private_rooms",
- # no useful index, but let's clear them anyway
- "appservice_room_list",
- "e2e_room_keys",
- "event_push_summary",
- "pusher_throttle",
- "group_summary_rooms",
- "room_account_data",
- "room_tags",
- "local_current_membership",
- ):
- logger.info("[purge] removing %s from %s", room_id, table)
- txn.execute("DELETE FROM %s WHERE room_id=?" % (table,), (room_id,))
-
- # Other tables we do NOT need to clear out:
- #
- # - blocked_rooms
- # This is important, to make sure that we don't accidentally rejoin a blocked
- # room after it was purged
- #
- # - user_directory
- # This has a room_id column, but it is unused
- #
-
- # Other tables that we might want to consider clearing out include:
- #
- # - event_reports
- # Given that these are intended for abuse management my initial
- # inclination is to leave them in place.
- #
- # - current_state_delta_stream
- # - ex_outlier_stream
- # - room_tags_revisions
- # The problem with these is that they are largeish and there is no room_id
- # index on them. In any case we should be clearing out 'stream' tables
- # periodically anyway (#5888)
-
- # TODO: we could probably usefully do a bunch more cache invalidation here
-
- # XXX: as with purge_history, this is racy, but no worse than other races
- # that already exist.
- self._invalidate_cache_and_stream(txn, self.have_seen_event, (room_id,))
-
- logger.info("[purge] done")
-
- return state_groups
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