Use execute_batch instead of executemany in places (#9181)

`execute_batch` does fewer round trips in postgres than `executemany`, but does not give a correct `txn.rowcount` result after.

changelog.d/9181.misc

@@ -0,0 +1 @@
+Speed up batch insertion when using PostgreSQL.

synapse/storage/database.py

@@ -267,8 +267,7 @@ class LoggingTransaction:
 
             self._do_execute(lambda *x: execute_batch(self.txn, *x), sql, args)
         else:
-            for val in args:
-                self.execute(sql, val)
+            self.executemany(sql, args)
 
     def execute_values(self, sql: str, *args: Any) -> List[Tuple]:
         """Corresponds to psycopg2.extras.execute_values. Only available when
@@ -888,7 +887,7 @@ class DatabasePool:
             ", ".join("?" for _ in keys[0]),
         )
 
-        txn.executemany(sql, vals)
+        txn.execute_batch(sql, vals)
 
     async def simple_upsert(
         self,

synapse/storage/databases/main/events.py

@@ -876,7 +876,7 @@ class PersistEventsStore:
                         WHERE room_id = ? AND type = ? AND state_key = ?
                     )
                 """
-                txn.executemany(
+                txn.execute_batch(
                     sql,
                     (
                         (
@@ -895,7 +895,7 @@ class PersistEventsStore:
                 )
                 # Now we actually update the current_state_events table
 
-                txn.executemany(
+                txn.execute_batch(
                     "DELETE FROM current_state_events"
                     " WHERE room_id = ? AND type = ? AND state_key = ?",
                     (
@@ -907,7 +907,7 @@ class PersistEventsStore:
                 # We include the membership in the current state table, hence we do
                 # a lookup when we insert. This assumes that all events have already
                 # been inserted into room_memberships.
-                txn.executemany(
+                txn.execute_batch(
                     """INSERT INTO current_state_events
                         (room_id, type, state_key, event_id, membership)
                     VALUES (?, ?, ?, ?, (SELECT membership FROM room_memberships WHERE event_id = ?))
@@ -927,7 +927,7 @@ class PersistEventsStore:
             # we have no record of the fact the user *was* a member of the
             # room but got, say, state reset out of it.
             if to_delete or to_insert:
-                txn.executemany(
+                txn.execute_batch(
                     "DELETE FROM local_current_membership"
                     " WHERE room_id = ? AND user_id = ?",
                     (
@@ -938,7 +938,7 @@ class PersistEventsStore:
                 )
 
             if to_insert:
-                txn.executemany(
+                txn.execute_batch(
                     """INSERT INTO local_current_membership
                         (room_id, user_id, event_id, membership)
                     VALUES (?, ?, ?, (SELECT membership FROM room_memberships WHERE event_id = ?))
@@ -1738,7 +1738,7 @@ class PersistEventsStore:
         """
 
         if events_and_contexts:
-            txn.executemany(
+            txn.execute_batch(
                 sql,
                 (
                     (
@@ -1767,7 +1767,7 @@ class PersistEventsStore:
 
         # Now we delete the staging area for *all* events that were being
         # persisted.
-        txn.executemany(
+        txn.execute_batch(
             "DELETE FROM event_push_actions_staging WHERE event_id = ?",
             ((event.event_id,) for event, _ in all_events_and_contexts),
         )
@@ -1886,7 +1886,7 @@ class PersistEventsStore:
             " )"
         )
 
-        txn.executemany(
+        txn.execute_batch(
             query,
             [
                 (e_id, ev.room_id, e_id, ev.room_id, e_id, ev.room_id, False)
@@ -1900,7 +1900,7 @@ class PersistEventsStore:
             "DELETE FROM event_backward_extremities"
             " WHERE event_id = ? AND room_id = ?"
         )
-        txn.executemany(
+        txn.execute_batch(
             query,
             [
                 (ev.event_id, ev.room_id)