Don't hit DB for noop replications queries

synapse/handlers/typing.py

@@ -221,6 +221,9 @@ class TypingHandler(object):
 
     def get_all_typing_updates(self, last_id, current_id):
         # TODO: Work out a way to do this without scanning the entire state.
+        if last_id == current_id:
+            return []
+
         rows = []
         for room_id, serial in self._room_serials.items():
             if last_id < serial and serial <= current_id:

synapse/storage/account_data.py

@@ -138,6 +138,9 @@ class AccountDataStore(SQLBaseStore):
             A deferred pair of lists of tuples of stream_id int, user_id string,
             room_id string, type string, and content string.
         """
+        if last_room_id == current_id and last_global_id == current_id:
+            return defer.succeed(([], []))
+
         def get_updated_account_data_txn(txn):
             sql = (
                 "SELECT stream_id, user_id, account_data_type, content"

synapse/storage/presence.py

@@ -118,6 +118,9 @@ class PresenceStore(SQLBaseStore):
             )
 
     def get_all_presence_updates(self, last_id, current_id):
+        if last_id == current_id:
+            return defer.succeed([])
+
         def get_all_presence_updates_txn(txn):
             sql = (
                 "SELECT stream_id, user_id, state, last_active_ts,"

synapse/storage/push_rule.py

@@ -421,6 +421,9 @@ class PushRuleStore(SQLBaseStore):
 
     def get_all_push_rule_updates(self, last_id, current_id, limit):
         """Get all the push rules changes that have happend on the server"""
+        if last_id == current_id:
+            return defer.succeed([])
+
         def get_all_push_rule_updates_txn(txn):
             sql = (
                 "SELECT stream_id, event_stream_ordering, user_id, rule_id,"

synapse/storage/tags.py

@@ -68,6 +68,9 @@ class TagsStore(SQLBaseStore):
             A deferred list of tuples of stream_id int, user_id string,
             room_id string, tag string and content string.
         """
+        if last_id == current_id:
+            defer.returnValue([])
+
         def get_all_updated_tags_txn(txn):
             sql = (
                 "SELECT stream_id, user_id, room_id"