Changes from self review

Signed-off-by: Matt Lord <mattalord@gmail.com>

go/test/endtoend/vtgate/keyspace_watches/keyspace_watch_test.go

@@ -140,6 +140,7 @@ func TestRoutingWithKeyspacesToWatch(t *testing.T) {
 }
 
 func TestVSchemaDDLWithKeyspacesToWatch(t *testing.T) {
+
 	extraVTGateArgs := []string{
 		"--vschema_ddl_authorized_users", "%",
 	}

go/test/endtoend/vtgate/vschema/vschema_test.go

@@ -35,6 +35,7 @@ import (
 	"vitess.io/vitess/go/mysql"
 	"vitess.io/vitess/go/test/endtoend/cluster"
 	"vitess.io/vitess/go/test/endtoend/utils"
+	"vitess.io/vitess/go/vt/vtgate"
 )
 
 var (
@@ -210,15 +211,15 @@ func TestVSchemaSQLAPIConcurrency(t *testing.T) {
 			_, err = mysqlConns[i].ExecuteFetch(fmt.Sprintf("ALTER VSCHEMA ADD TABLE %s", tableName), -1, false)
 			if err != nil {
 				// The error we get is an SQL error so we have to do string matching.
-				if err != nil && strings.Contains(err.Error(), "failed to update vschema as the session's version was stale") {
+				if err != nil && strings.Contains(err.Error(), vtgate.ErrStaleVSchema.Error()) {
 					preventedLostWrites = true
 				}
 			} else {
 				require.NoError(t, err)
 				time.Sleep(time.Duration(rand.Intn(1000) * int(time.Nanosecond)))
 				_, err = mysqlConns[i].ExecuteFetch(fmt.Sprintf("ALTER VSCHEMA DROP TABLE %s", tableName), -1, false)
 				// The error we get is an SQL error so we have to do string matching.
-				if err != nil && strings.Contains(err.Error(), "failed to update vschema as the session's version was stale") {
+				if err != nil && strings.Contains(err.Error(), vtgate.ErrStaleVSchema.Error()) {
 					preventedLostWrites = true
 				} else {
 					require.NoError(t, err)

go/vt/topo/srv_vschema.go

@@ -175,12 +175,8 @@ func (ts *Server) RebuildSrvVSchema(ctx context.Context, cells []string) error {
 			if IsErrType(err, NoNode) {
 				err = nil
 				ksvs = &KeyspaceVSchemaInfo{
-					Name: keyspace,
-					Keyspace: &vschemapb.Keyspace{
-						Sharded:  false,
-						Vindexes: make(map[string]*vschemapb.Vindex),
-						Tables:   make(map[string]*vschemapb.Table),
-					},
+					Name:     keyspace,
+					Keyspace: &vschemapb.Keyspace{},
 				}
 			}
 

go/vt/vtgate/executorcontext/vcursor_impl.go

@@ -1406,7 +1406,8 @@ func (vc *VCursorImpl) ExecuteVSchema(ctx context.Context, keyspace string, vsch
 			return err
 		}
 	} else {
-		// Use the cached version.
+		// Use the cached version as we are in read-only mode
+		// and any writes would fail.
 		ksvs.Name = ksName
 		ksvs.Keyspace = srvVschema.Keyspaces[ksName]
 	}