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# Copyright 2019 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 itertools
import logging
from typing import TYPE_CHECKING, Set
from synapse.logging.context import nested_logging_context
from synapse.storage.databases import Databases
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
class PurgeEventsStorageController:
"""High level interface for purging rooms and event history."""
def __init__(self, hs: "HomeServer", stores: Databases):
self.stores = stores
async def purge_room(self, room_id: str) -> None:
"""Deletes all record of a room"""
with nested_logging_context(room_id):
state_groups_to_delete = await self.stores.main.purge_room(room_id)
await self.stores.state.purge_room_state(room_id, state_groups_to_delete)
async def purge_history(
self, room_id: str, token: str, delete_local_events: bool
) -> None:
"""Deletes room history before a certain point
Args:
room_id: The 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).
"""
with nested_logging_context(room_id):
state_groups = await self.stores.main.purge_history(
room_id, token, delete_local_events
)
logger.info("[purge] finding state groups that can be deleted")
sg_to_delete = await self._find_unreferenced_groups(state_groups)
await self.stores.state.purge_unreferenced_state_groups(
room_id, sg_to_delete
)
async def _find_unreferenced_groups(self, state_groups: Set[int]) -> Set[int]:
"""Used when purging history to figure out which state groups can be
deleted.
Args:
state_groups: Set of state groups referenced by events
that are going to be deleted.
Returns:
The set of state groups that can be deleted.
"""
# Set of events that we have found to be referenced by events
referenced_groups = set()
# Set of state groups we've already seen
state_groups_seen = set(state_groups)
# Set of state groups to handle next.
next_to_search = set(state_groups)
while next_to_search:
# We bound size of groups we're looking up at once, to stop the
# SQL query getting too big
if len(next_to_search) < 100:
current_search = next_to_search
next_to_search = set()
else:
current_search = set(itertools.islice(next_to_search, 100))
next_to_search -= current_search
referenced = await self.stores.main.get_referenced_state_groups(
current_search
)
referenced_groups |= referenced
# We don't continue iterating up the state group graphs for state
# groups that are referenced.
current_search -= referenced
edges = await self.stores.state.get_previous_state_groups(current_search)
prevs = set(edges.values())
# We don't bother re-handling groups we've already seen
prevs -= state_groups_seen
next_to_search |= prevs
state_groups_seen |= prevs
to_delete = state_groups_seen - referenced_groups
return to_delete
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