1 files changed, 70 insertions, 0 deletions
diff --git a/synapse/storage/schema/main/delta/78/05_mitigate_stream_ordering_update_race.py b/synapse/storage/schema/main/delta/78/05_mitigate_stream_ordering_update_race.py
new file mode 100644
index 0000000000..1a22f6a404
--- /dev/null
+++ b/synapse/storage/schema/main/delta/78/05_mitigate_stream_ordering_update_race.py
@@ -0,0 +1,70 @@
+# 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.
+
+
+from synapse.storage.database import LoggingTransaction
+from synapse.storage.engines import BaseDatabaseEngine, PostgresEngine
+
+
+def run_create(
+ cur: LoggingTransaction,
+ database_engine: BaseDatabaseEngine,
+) -> None:
+ """
+ An attempt to mitigate a painful race between foreground and background updates
+ touching the `stream_ordering` column of the events table. More info can be found
+ at https://github.com/matrix-org/synapse/issues/15677.
+ """
+
+ # technically the bg update we're concerned with below should only have been added in
+ # postgres but it doesn't hurt to be extra careful
+ if isinstance(database_engine, PostgresEngine):
+ select_sql = """
+ SELECT 1 FROM background_updates
+ WHERE update_name = 'replace_stream_ordering_column'
+ """
+ cur.execute(select_sql)
+ res = cur.fetchone()
+
+ # if the background update `replace_stream_ordering_column` is still pending, we need
+ # to drop the indexes added in 7403, and re-add them to the column `stream_ordering2`
+ # with the idea that they will be preserved when the column is renamed `stream_ordering`
+ # after the background update has finished
+ if res:
+ drop_cse_sql = """
+ ALTER TABLE current_state_events DROP CONSTRAINT event_stream_ordering_fkey
+ """
+ cur.execute(drop_cse_sql)
+
+ drop_lcm_sql = """
+ ALTER TABLE local_current_membership DROP CONSTRAINT event_stream_ordering_fkey
+ """
+ cur.execute(drop_lcm_sql)
+
+ drop_rm_sql = """
+ ALTER TABLE room_memberships DROP CONSTRAINT event_stream_ordering_fkey
+ """
+ cur.execute(drop_rm_sql)
+
+ add_cse_sql = """
+ ALTER TABLE current_state_events ADD CONSTRAINT event_stream_ordering_fkey
+ FOREIGN KEY (event_stream_ordering) REFERENCES events(stream_ordering2) NOT VALID;
+ """
+ cur.execute(add_cse_sql)
+
+ add_lcm_sql = """
+ ALTER TABLE local_current_membership ADD CONSTRAINT event_stream_ordering_fkey
+ FOREIGN KEY (event_stream_ordering) REFERENCES events(stream_ordering2) NOT VALID;
+ """
+ cur.execute(add_lcm_sql)
+
+ add_rm_sql = """
+ ALTER TABLE room_memberships ADD CONSTRAINT event_stream_ordering_fkey
+ FOREIGN KEY (event_stream_ordering) REFERENCES events(stream_ordering2) NOT VALID;
+ """
+ cur.execute(add_rm_sql)
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