after a few rethinks, a working implementation of pushers.

synapse/storage/_base.py

@@ -195,6 +195,51 @@ class SQLBaseStore(object):
         txn.execute(sql, values.values())
         return txn.lastrowid
 
+    def _simple_upsert(self, table, keyvalues, values):
+        """
+        :param table: The table to upsert into
+        :param keyvalues: Dict of the unique key tables and their new values
+        :param values: Dict of all the nonunique columns and their new values
+        :return: A deferred
+        """
+        return self.runInteraction(
+            "_simple_upsert",
+            self._simple_upsert_txn, table, keyvalues, values
+        )
+
+    def _simple_upsert_txn(self, txn, table, keyvalues, values):
+        # Try to update
+        sql = "UPDATE %s SET %s WHERE %s" % (
+            table,
+            ", ".join("%s = ?" % (k) for k in values),
+            " AND ".join("%s = ?" % (k) for k in keyvalues)
+        )
+        sqlargs = values.values() + keyvalues.values()
+        logger.debug(
+            "[SQL] %s Args=%s",
+            sql, sqlargs,
+        )
+
+        txn.execute(sql, sqlargs)
+        if txn.rowcount == 0:
+            # We didn't update and rows so insert a new one
+            allvalues = {}
+            allvalues.update(keyvalues)
+            allvalues.update(values)
+
+            sql = "INSERT INTO %s (%s) VALUES (%s)" % (
+                table,
+                ", ".join(k for k in allvalues),
+                ", ".join("?" for _ in allvalues)
+            )
+            logger.debug(
+                "[SQL] %s Args=%s",
+                sql, keyvalues.values(),
+            )
+            txn.execute(sql, allvalues.values())
+
+
+
     def _simple_select_one(self, table, keyvalues, retcols,
                            allow_none=False):
         """Executes a SELECT query on the named table, which is expected to