Move _get_cache_dict into the SQLBaseStore

synapse/storage/__init__.py

@@ -177,39 +177,6 @@ class DataStore(RoomMemberStore, RoomStore,
         self.__presence_on_startup = None
         return active_on_startup
 
-    def _get_cache_dict(self, db_conn, table, entity_column, stream_column, max_value):
-        # Fetch a mapping of room_id -> max stream position for "recent" rooms.
-        # It doesn't really matter how many we get, the StreamChangeCache will
-        # do the right thing to ensure it respects the max size of cache.
-        sql = (
-            "SELECT %(entity)s, MAX(%(stream)s) FROM %(table)s"
-            " WHERE %(stream)s > ? - 100000"
-            " GROUP BY %(entity)s"
-        ) % {
-            "table": table,
-            "entity": entity_column,
-            "stream": stream_column,
-        }
-
-        sql = self.database_engine.convert_param_style(sql)
-
-        txn = db_conn.cursor()
-        txn.execute(sql, (int(max_value),))
-        rows = txn.fetchall()
-        txn.close()
-
-        cache = {
-            row[0]: int(row[1])
-            for row in rows
-        }
-
-        if cache:
-            min_val = min(cache.values())
-        else:
-            min_val = max_value
-
-        return cache, min_val
-
     def _get_active_presence(self, db_conn):
         """Fetch non-offline presence from the database so that we can register
         the appropriate time outs.

synapse/storage/_base.py

@@ -816,6 +816,40 @@ class SQLBaseStore(object):
             self._next_stream_id += 1
             return i
 
+    def _get_cache_dict(self, db_conn, table, entity_column, stream_column,
+                        max_value):
+        # Fetch a mapping of room_id -> max stream position for "recent" rooms.
+        # It doesn't really matter how many we get, the StreamChangeCache will
+        # do the right thing to ensure it respects the max size of cache.
+        sql = (
+            "SELECT %(entity)s, MAX(%(stream)s) FROM %(table)s"
+            " WHERE %(stream)s > ? - 100000"
+            " GROUP BY %(entity)s"
+        ) % {
+            "table": table,
+            "entity": entity_column,
+            "stream": stream_column,
+        }
+
+        sql = self.database_engine.convert_param_style(sql)
+
+        txn = db_conn.cursor()
+        txn.execute(sql, (int(max_value),))
+        rows = txn.fetchall()
+        txn.close()
+
+        cache = {
+            row[0]: int(row[1])
+            for row in rows
+        }
+
+        if cache:
+            min_val = min(cache.values())
+        else:
+            min_val = max_value
+
+        return cache, min_val
+
 
 class _RollbackButIsFineException(Exception):
     """ This exception is used to rollback a transaction without implying