Enable WAL for SQLite

Signed-off-by: Lorenzo Manacorda <[email protected]>

synapse/storage/engines/sqlite.py

@@ -88,6 +88,10 @@ def on_new_connection(self, db_conn: "LoggingDatabaseConnection") -> None:
 
         db_conn.create_function("rank", 1, _rank)
         db_conn.execute("PRAGMA foreign_keys = ON;")
+
+        # Enable WAL.
+        # see https://www.sqlite.org/wal.html
+        db_conn.execute("PRAGMA journal_mode = WAL;")
         db_conn.commit()
 
     def is_deadlock(self, error: Exception) -> bool: