1 files changed, 31 insertions, 4 deletions
diff --git a/synapse/storage/registration.py b/synapse/storage/registration.py
index 2dd14aba1c..80d76bf9d7 100644
--- a/synapse/storage/registration.py
+++ b/synapse/storage/registration.py
@@ -474,17 +474,44 @@ class RegistrationStore(RegistrationWorkerStore,
 
     @defer.inlineCallbacks
     def get_user_id_by_threepid(self, medium, address):
-        ret = yield self._simple_select_one(
+        """Returns user id from threepid
+
+        Args:
+            medium (str): threepid medium e.g. email
+            address (str): threepid address e.g. me@example.com
+
+        Returns:
+            Deferred[str|None]: user id or None if no user id/threepid mapping exists
+        """
+        user_id = yield self.runInteraction(
+            "get_user_id_by_threepid", self.get_user_id_by_threepid_txn,
+            medium, address
+        )
+        defer.returnValue(user_id)
+
+    def get_user_id_by_threepid_txn(self, txn, medium, address):
+        """Returns user id from threepid
+
+        Args:
+            txn (cursor):
+            medium (str): threepid medium e.g. email
+            address (str): threepid address e.g. me@example.com
+
+        Returns:
+            str|None: user id or None if no user id/threepid mapping exists
+        """
+        ret = self._simple_select_one_txn(
+            txn,
             "user_threepids",
             {
                 "medium": medium,
                 "address": address
             },
-            ['user_id'], True, 'get_user_id_by_threepid'
+            ['user_id'], True
         )
         if ret:
-            defer.returnValue(ret['user_id'])
-        defer.returnValue(None)
+            return ret['user_id']
+        return None
 
     def user_delete_threepid(self, user_id, medium, address):
         return self._simple_delete(