1 files changed, 112 insertions, 0 deletions
diff --git a/synapse/storage/controllers/purge_events.py b/synapse/storage/controllers/purge_events.py
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+++ b/synapse/storage/controllers/purge_events.py
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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.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"""
+
+        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).
+        """
+        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