@Override
  public boolean namespaceExists(Namespace namespace) {
    return JdbcUtil.namespaceExists(catalogName, connections, namespace);
  }
@Test
  public void testNamespaceExists() {
    TableIdentifier tbl1 = TableIdentifier.of("db", "ns1", "ns2", "metadata");
    TableIdentifier tbl2 = TableIdentifier.of("db", "ns2", "ns3", "tbl2");
    TableIdentifier tbl3 = TableIdentifier.of("db", "ns3", "tbl4");
    TableIdentifier tbl4 = TableIdentifier.of("db", "metadata");

    Lists.newArrayList(tbl1, tbl2, tbl3, tbl4)
        .forEach(t -> catalog.createTable(t, SCHEMA, PartitionSpec.unpartitioned()));
    assertThat(catalog.namespaceExists(Namespace.of("db", "ns1", "ns2")))
        .as("Should true to namespace exist")
        .isTrue();
    assertThat(catalog.namespaceExists(Namespace.of("db", "db2", "not_exist")))
        .as("Should false to namespace doesn't exist")
        .isFalse();
  }