Clear keyspace schema in vtgate before re-loading it

Signed-off-by: Matt Lord <[email protected]>

go/vt/vtgate/schema/tracker.go

@@ -84,9 +84,14 @@ func (t *Tracker) LoadKeyspace(conn queryservice.QueryService, target *querypb.T
 	}
 	t.mu.Lock()
 	defer t.mu.Unlock()
+	// We must clear out any previous schema before loading it here as this is called
+	// whenever a shard's primary tablet starts and sends the initial signal. Without
+	// clearing out the previous schema we can end up with duplicate entries when the
+	// tablet is simply restarted or potentially when we elect a new primary.
+	t.clearKeyspaceTables(target.Keyspace)
 	t.updateTables(target.Keyspace, res)
 	t.tracked[target.Keyspace].setLoaded(true)
-	log.Infof("finished loading schema for keyspace %s. Found %d tables", target.Keyspace, len(res.Rows))
+	log.Infof("finished loading schema for keyspace %s. Found %d columns in total across the tables", target.Keyspace, len(res.Rows))
 	return nil
 }
 
@@ -128,6 +133,7 @@ func (t *Tracker) newUpdateController() *updateController {
 }
 
 func (t *Tracker) initKeyspace(th *discovery.TabletHealth) error {
+
 	err := t.LoadKeyspace(th.Conn, th.Target)
 	if err != nil {
 		log.Warningf("Unable to add keyspace to tracker: %v", err)
@@ -255,3 +261,12 @@ func (tm *tableMap) delete(ks, tbl string) {
 	}
 	delete(m, tbl)
 }
+
+// This empties out any previous schema for for all tables in a keyspace
+// You should call this before initializing/loading a keyspace of the same
+// name in the cache
+func (t *Tracker) clearKeyspaceTables(ks string) {
+	if t.tables != nil {
+		delete(t.tables.m, ks)
+	}
+}

go/vt/vtgate/schema/update_controller_flaky_test.go

@@ -124,7 +124,7 @@ func TestMultipleUpdatesFromDifferentShards(t *testing.T) {
 			signal := func() {
 				signalNb++
 			}
-			kUpdate := updateController{
+			updateCont := updateController{
 				update:       update,
 				signal:       signal,
 				consumeDelay: 5 * time.Millisecond,
@@ -159,13 +159,13 @@ func TestMultipleUpdatesFromDifferentShards(t *testing.T) {
 				if test.delay > 0 {
 					time.Sleep(test.delay)
 				}
-				kUpdate.add(d)
+				updateCont.add(d)
 			}
 
 			for {
-				kUpdate.mu.Lock()
-				done := kUpdate.queue == nil
-				kUpdate.mu.Unlock()
+				updateCont.mu.Lock()
+				done := updateCont.queue == nil
+				updateCont.mu.Unlock()
 				if done {
 					break
 				}