Add no_scatter flag to vttestserver

go/cmd/vttestserver/cli/main.go

@@ -224,6 +224,8 @@ func New() (cmd *cobra.Command) {
 	cmd.Flags().DurationVar(&config.VtgateTabletRefreshInterval, "tablet_refresh_interval", 10*time.Second, "Interval at which vtgate refreshes tablet information from topology server.")
 
 	cmd.Flags().BoolVar(&doCreateTCPUser, "initialize-with-vt-dba-tcp", false, "If this flag is enabled, MySQL will be initialized with an additional user named vt_dba_tcp, who will have access via TCP/IP connection.")
+
+	cmd.Flags().BoolVar(&config.NoScatter, "no_scatter", false, "when set to true, the planner will fail instead of producing a plan that includes scatter queries")
 	acl.RegisterFlags(cmd.Flags())
 
 	return cmd

go/cmd/vttestserver/cli/main_test.go

@@ -186,6 +186,21 @@ func TestForeignKeysAndDDLModes(t *testing.T) {
 	assert.NoError(t, err)
 }
 
+func TestNoScatter(t *testing.T) {
+	conf := config
+	defer resetConfig(conf)
+
+	cluster, err := startCluster("--no_scatter")
+	assert.NoError(t, err)
+	defer cluster.TearDown()
+
+	_ = execOnCluster(cluster, "app_customer", func(conn *mysql.Conn) error {
+		_, err = conn.ExecuteFetch("SELECT * FROM customers", 100, false)
+		require.ErrorContains(t, err, "plan includes scatter, which is disallowed")
+		return nil
+	})
+}
+
 // TestCreateDbaTCPUser tests that the vt_dba_tcp user is created and can connect through TCP/IP connection
 // when --initialize-with-vt-dba-tcp is set to true.
 func TestCreateDbaTCPUser(t *testing.T) {

go/flags/endtoend/vttestserver.txt

@@ -92,6 +92,7 @@ Flags:
       --mysql_server_version string                                      MySQL server version to advertise. (default "8.0.30-Vitess")
       --mysqlctl_mycnf_template string                                   template file to use for generating the my.cnf file during server init
       --mysqlctl_socket string                                           socket file to use for remote mysqlctl actions (empty for local actions)
+      --no_scatter                                                       when set to true, the planner will fail instead of producing a plan that includes scatter queries
       --null_probability float                                           The probability to initialize a field with 'NULL'  if --initialize_with_random_data is true. Only applies to fields that can contain NULL values. (default 0.1)
       --num_shards strings                                               Comma separated shard count (one per keyspace) (default [2])
       --onclose_timeout duration                                         wait no more than this for OnClose handlers before stopping (default 10s)

go/vt/vttest/local_cluster.go

@@ -156,6 +156,9 @@ type Config struct {
 	ExternalTopoGlobalRoot string
 
 	VtgateTabletRefreshInterval time.Duration
+
+	// Set the planner to fail on scatter queries
+	NoScatter bool
 }
 
 // InitSchemas is a shortcut for tests that just want to setup a single

go/vt/vttest/vtprocess.go

@@ -235,6 +235,7 @@ func VtcomboProcess(environment Environment, args *Config, mysql MySQLManager) (
 		fmt.Sprintf("--enable_online_ddl=%t", args.EnableOnlineDDL),
 		fmt.Sprintf("--enable_direct_ddl=%t", args.EnableDirectDDL),
 		fmt.Sprintf("--enable_system_settings=%t", args.EnableSystemSettings),
+		fmt.Sprintf("--no_scatter=%t", args.NoScatter),
 	}...)
 
 	// If topo tablet refresh interval is not defined then we will give it value of 10s. Please note