presto-hive/src/main/java/io/prestosql/plugin/hive/HiveMetadata.java/HiveMetadata/listSchemas
class HiveMetadata:    private List<String> listSchemas(ConnectorSession session, Optional<String> schemaName)
    {
        if (schemaName.isPresent()) {
            return ImmutableList.of(schemaName.get());
        }
        return listSchemaNames(session);
    }