Replace `room_depth.min_depth` with a BIGINT (#10289)

while I'm dealing with INTEGERs and BIGINTs, let's replace room_depth.min_depth
with a BIGINT.

4 files changed, 186 insertions, 7 deletions

diff --git a/changelog.d/10289.misc b/changelog.d/10289.misc
new file mode 100644
index 0000000000..2df30e7a7a
--- /dev/null
+++ b/changelog.d/10289.misc
@@ -0,0 +1 @@
+Convert `room_depth.min_depth` column to a `BIGINT`.
diff --git a/synapse/storage/databases/main/room.py b/synapse/storage/databases/main/room.py
index 9f0d64a325..6ddafe5434 100644
--- a/synapse/storage/databases/main/room.py
+++ b/synapse/storage/databases/main/room.py
@@ -25,6 +25,7 @@ from synapse.api.room_versions import RoomVersion, RoomVersions
 from synapse.storage._base import SQLBaseStore, db_to_json
 from synapse.storage.database import DatabasePool, LoggingTransaction
 from synapse.storage.databases.main.search import SearchStore
+from synapse.storage.types import Cursor
 from synapse.types import JsonDict, ThirdPartyInstanceID
 from synapse.util import json_encoder
 from synapse.util.caches.descriptors import cached
@@ -1022,10 +1023,22 @@ class RoomWorkerStore(SQLBaseStore):
         )
 
 
-class RoomBackgroundUpdateStore(SQLBaseStore):
+class _BackgroundUpdates:
     REMOVE_TOMESTONED_ROOMS_BG_UPDATE = "remove_tombstoned_rooms_from_directory"
     ADD_ROOMS_ROOM_VERSION_COLUMN = "add_rooms_room_version_column"
+    POPULATE_ROOM_DEPTH_MIN_DEPTH2 = "populate_room_depth_min_depth2"
+    REPLACE_ROOM_DEPTH_MIN_DEPTH = "replace_room_depth_min_depth"
+
+
+_REPLACE_ROOM_DEPTH_SQL_COMMANDS = (
+    "DROP TRIGGER populate_min_depth2_trigger ON room_depth",
+    "DROP FUNCTION populate_min_depth2()",
+    "ALTER TABLE room_depth DROP COLUMN min_depth",
+    "ALTER TABLE room_depth RENAME COLUMN min_depth2 TO min_depth",
+)
+
 
+class RoomBackgroundUpdateStore(SQLBaseStore):
     def __init__(self, database: DatabasePool, db_conn, hs):
         super().__init__(database, db_conn, hs)
 
@@ -1037,15 +1050,25 @@ class RoomBackgroundUpdateStore(SQLBaseStore):
         )
 
         self.db_pool.updates.register_background_update_handler(
-            self.REMOVE_TOMESTONED_ROOMS_BG_UPDATE,
+            _BackgroundUpdates.REMOVE_TOMESTONED_ROOMS_BG_UPDATE,
             self._remove_tombstoned_rooms_from_directory,
         )
 
         self.db_pool.updates.register_background_update_handler(
-            self.ADD_ROOMS_ROOM_VERSION_COLUMN,
+            _BackgroundUpdates.ADD_ROOMS_ROOM_VERSION_COLUMN,
             self._background_add_rooms_room_version_column,
         )
 
+        # BG updates to change the type of room_depth.min_depth
+        self.db_pool.updates.register_background_update_handler(
+            _BackgroundUpdates.POPULATE_ROOM_DEPTH_MIN_DEPTH2,
+            self._background_populate_room_depth_min_depth2,
+        )
+        self.db_pool.updates.register_background_update_handler(
+            _BackgroundUpdates.REPLACE_ROOM_DEPTH_MIN_DEPTH,
+            self._background_replace_room_depth_min_depth,
+        )
+
     async def _background_insert_retention(self, progress, batch_size):
         """Retrieves a list of all rooms within a range and inserts an entry for each of
         them into the room_retention table.
@@ -1164,7 +1187,9 @@ class RoomBackgroundUpdateStore(SQLBaseStore):
                 new_last_room_id = room_id
 
             self.db_pool.updates._background_update_progress_txn(
-                txn, self.ADD_ROOMS_ROOM_VERSION_COLUMN, {"room_id": new_last_room_id}
+                txn,
+                _BackgroundUpdates.ADD_ROOMS_ROOM_VERSION_COLUMN,
+                {"room_id": new_last_room_id},
             )
 
             return False
@@ -1176,7 +1201,7 @@ class RoomBackgroundUpdateStore(SQLBaseStore):
 
         if end:
             await self.db_pool.updates._end_background_update(
-                self.ADD_ROOMS_ROOM_VERSION_COLUMN
+                _BackgroundUpdates.ADD_ROOMS_ROOM_VERSION_COLUMN
             )
 
         return batch_size
@@ -1215,7 +1240,7 @@ class RoomBackgroundUpdateStore(SQLBaseStore):
 
         if not rooms:
             await self.db_pool.updates._end_background_update(
-                self.REMOVE_TOMESTONED_ROOMS_BG_UPDATE
+                _BackgroundUpdates.REMOVE_TOMESTONED_ROOMS_BG_UPDATE
             )
             return 0
 
@@ -1224,7 +1249,7 @@ class RoomBackgroundUpdateStore(SQLBaseStore):
             await self.set_room_is_public(room_id, False)
 
         await self.db_pool.updates._background_update_progress(
-            self.REMOVE_TOMESTONED_ROOMS_BG_UPDATE, {"room_id": rooms[-1]}
+            _BackgroundUpdates.REMOVE_TOMESTONED_ROOMS_BG_UPDATE, {"room_id": rooms[-1]}
         )
 
         return len(rooms)
@@ -1268,6 +1293,71 @@ class RoomBackgroundUpdateStore(SQLBaseStore):
 
         return max_ordering is None
 
+    async def _background_populate_room_depth_min_depth2(
+        self, progress: JsonDict, batch_size: int
+    ) -> int:
+        """Populate room_depth.min_depth2
+
+        This is to deal with the fact that min_depth was initially created as a
+        32-bit integer field.
+        """
+
+        def process(txn: Cursor) -> int:
+            last_room = progress.get("last_room", "")
+            txn.execute(
+                """
+                UPDATE room_depth SET min_depth2=min_depth
+                WHERE room_id IN (
+                   SELECT room_id FROM room_depth WHERE room_id > ?
+                   ORDER BY room_id LIMIT ?
+                )
+                RETURNING room_id;
+                """,
+                (last_room, batch_size),
+            )
+            row_count = txn.rowcount
+            if row_count == 0:
+                return 0
+            last_room = max(row[0] for row in txn)
+            logger.info("populated room_depth up to %s", last_room)
+
+            self.db_pool.updates._background_update_progress_txn(
+                txn,
+                _BackgroundUpdates.POPULATE_ROOM_DEPTH_MIN_DEPTH2,
+                {"last_room": last_room},
+            )
+            return row_count
+
+        result = await self.db_pool.runInteraction(
+            "_background_populate_min_depth2", process
+        )
+
+        if result != 0:
+            return result
+
+        await self.db_pool.updates._end_background_update(
+            _BackgroundUpdates.POPULATE_ROOM_DEPTH_MIN_DEPTH2
+        )
+        return 0
+
+    async def _background_replace_room_depth_min_depth(
+        self, progress: JsonDict, batch_size: int
+    ) -> int:
+        """Drop the old 'min_depth' column and rename 'min_depth2' into its place."""
+
+        def process(txn: Cursor) -> None:
+            for sql in _REPLACE_ROOM_DEPTH_SQL_COMMANDS:
+                logger.info("completing room_depth migration: %s", sql)
+                txn.execute(sql)
+
+        await self.db_pool.runInteraction("_background_replace_room_depth", process)
+
+        await self.db_pool.updates._end_background_update(
+            _BackgroundUpdates.REPLACE_ROOM_DEPTH_MIN_DEPTH,
+        )
+
+        return 0
+
 
 class RoomStore(RoomBackgroundUpdateStore, RoomWorkerStore, SearchStore):
     def __init__(self, database: DatabasePool, db_conn, hs):
diff --git a/synapse/storage/schema/main/delta/61/02drop_redundant_room_depth_index.sql b/synapse/storage/schema/main/delta/61/02drop_redundant_room_depth_index.sql
new file mode 100644
index 0000000000..35ca7a40c0
--- /dev/null
+++ b/synapse/storage/schema/main/delta/61/02drop_redundant_room_depth_index.sql
@@ -0,0 +1,18 @@
+/* Copyright 2021 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.
+ */
+
+-- this index is redundant; there is another UNIQUE index on this table.
+DROP INDEX IF EXISTS room_depth_room;
+
diff --git a/synapse/storage/schema/main/delta/61/03recreate_min_depth.py b/synapse/storage/schema/main/delta/61/03recreate_min_depth.py
new file mode 100644
index 0000000000..f8d7db9f2e
--- /dev/null
+++ b/synapse/storage/schema/main/delta/61/03recreate_min_depth.py
@@ -0,0 +1,70 @@
+# Copyright 2021 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.
+
+"""
+This migration handles the process of changing the type of `room_depth.min_depth` to
+a BIGINT.
+"""
+from synapse.storage.engines import BaseDatabaseEngine, PostgresEngine
+from synapse.storage.types import Cursor
+
+
+def run_create(cur: Cursor, database_engine: BaseDatabaseEngine, *args, **kwargs):
+    if not isinstance(database_engine, PostgresEngine):
+        # this only applies to postgres - sqlite does not distinguish between big and
+        # little ints.
+        return
+
+    # First add a new column to contain the bigger min_depth
+    cur.execute("ALTER TABLE room_depth ADD COLUMN min_depth2 BIGINT")
+
+    # Create a trigger which will keep it populated.
+    cur.execute(
+        """
+        CREATE OR REPLACE FUNCTION populate_min_depth2() RETURNS trigger AS $BODY$
+            BEGIN
+                new.min_depth2 := new.min_depth;
+                RETURN NEW;
+            END;
+        $BODY$ LANGUAGE plpgsql
+        """
+    )
+
+    cur.execute(
+        """
+        CREATE TRIGGER populate_min_depth2_trigger BEFORE INSERT OR UPDATE ON room_depth
+        FOR EACH ROW
+        EXECUTE PROCEDURE populate_min_depth2()
+        """
+    )
+
+    # Start a bg process to populate it for old rooms
+    cur.execute(
+        """
+       INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
+            (6103, 'populate_room_depth_min_depth2', '{}')
+       """
+    )
+
+    # and another to switch them over once it completes.
+    cur.execute(
+        """
+        INSERT INTO background_updates (ordering, update_name, progress_json, depends_on) VALUES
+            (6103, 'replace_room_depth_min_depth', '{}', 'populate_room_depth2')
+        """
+    )
+
+
+def run_upgrade(cur: Cursor, database_engine: BaseDatabaseEngine, *args, **kwargs):
+    pass