Avoid executing no-op queries.

Author: clokep

synapse/storage/database.py

@@ -1132,7 +1132,7 @@ def simple_insert_many_txn(
         txn: LoggingTransaction,
         table: str,
         keys: Collection[str],
-        values: Iterable[Iterable[Any]],
+        values: Collection[Iterable[Any]],
     ) -> None:
         """Executes an INSERT query on the named table.
 
@@ -1145,6 +1145,9 @@ def simple_insert_many_txn(
             keys: list of column names
             values: for each row, a list of values in the same order as `keys`
         """
+        # IF there's nothing to insert, don't send the query.
+        if not values:
+            return
 
         if isinstance(txn.database_engine, PostgresEngine):
             # We use `execute_values` as it can be a lot faster than `execute_batch`,
@@ -1470,7 +1473,7 @@ def simple_upsert_many_txn(
         key_names: Collection[str],
         key_values: Collection[Iterable[Any]],
         value_names: Collection[str],
-        value_values: Iterable[Iterable[Any]],
+        value_values: Collection[Iterable[Any]],
     ) -> None:
         """
         Upsert, many times.
@@ -1483,6 +1486,9 @@ def simple_upsert_many_txn(
             value_values: A list of each row's value column values.
                 Ignored if value_names is empty.
         """
+        if not value_values:
+            return
+
         if table not in self._unsafe_to_upsert_tables:
             return self.simple_upsert_many_txn_native_upsert(
                 txn, table, key_names, key_values, value_names, value_values
@@ -2059,6 +2065,8 @@ def simple_update_many_txn(
             raise ValueError(
                 f"{len(key_values)} key rows and {len(value_values)} value rows: should be the same number."
             )
+        if not value_values:
+            return
 
         # List of tuples of (value values, then key values)
         # (This matches the order needed for the query)

synapse/storage/databases/main/devices.py

@@ -703,7 +703,7 @@ def _mark_as_sent_devices_by_remote_txn(
             key_names=("destination", "user_id"),
             key_values=[(destination, user_id) for user_id, _ in rows],
             value_names=("stream_id",),
-            value_values=((stream_id,) for _, stream_id in rows),
+            value_values=[(stream_id,) for _, stream_id in rows],
         )
 
         # Delete all sent outbound pokes

synapse/storage/databases/main/events.py

@@ -1454,7 +1454,7 @@ def event_dict(event: EventBase) -> JsonDict:
             txn,
             table="event_json",
             keys=("event_id", "room_id", "internal_metadata", "json", "format_version"),
-            values=(
+            values=[
                 (
                     event.event_id,
                     event.room_id,
@@ -1463,7 +1463,7 @@ def event_dict(event: EventBase) -> JsonDict:
                     event.format_version,
                 )
                 for event, _ in events_and_contexts
-            ),
+            ],
         )
 
         self.db_pool.simple_insert_many_txn(
@@ -1486,7 +1486,7 @@ def event_dict(event: EventBase) -> JsonDict:
                 "state_key",
                 "rejection_reason",
             ),
-            values=(
+            values=[
                 (
                     self._instance_name,
                     event.internal_metadata.stream_ordering,
@@ -1505,7 +1505,7 @@ def event_dict(event: EventBase) -> JsonDict:
                     context.rejected,
                 )
                 for event, context in events_and_contexts
-            ),
+            ],
         )
 
         # If we're persisting an unredacted event we go and ensure
@@ -1528,11 +1528,11 @@ def event_dict(event: EventBase) -> JsonDict:
             txn,
             table="state_events",
             keys=("event_id", "room_id", "type", "state_key"),
-            values=(
+            values=[
                 (event.event_id, event.room_id, event.type, event.state_key)
                 for event, _ in events_and_contexts
                 if event.is_state()
-            ),
+            ],
         )
 
     def _store_rejected_events_txn(

synapse/storage/databases/main/room.py

@@ -2216,7 +2216,7 @@ def _store_partial_state_room_txn(
             txn,
             table="partial_state_rooms_servers",
             keys=("room_id", "server_name"),
-            values=((room_id, s) for s in servers),
+            values=[(room_id, s) for s in servers],
         )
         self._invalidate_cache_and_stream(txn, self.is_partial_state_room, (room_id,))
         self._invalidate_cache_and_stream(

synapse/storage/databases/main/search.py

@@ -106,15 +106,15 @@ def store_search_entries_txn(
                 txn,
                 table="event_search",
                 keys=("event_id", "room_id", "key", "value"),
-                values=(
+                values=[
                     (
                         entry.event_id,
                         entry.room_id,
                         entry.key,
                         _clean_value_for_search(entry.value),
                     )
                     for entry in entries
-                ),
+                ],
             )
 
         else: