code: protected function findViewNames($schema = '')
      {
          if ($schema === '') {
              $schema = $this->defaultSchema;
          }
          $sql = <<<'SQL'
  SELECT c.relname AS table_name
  FROM pg_class c
  INNER JOIN pg_namespace ns ON ns.oid = c.relnamespace
  WHERE ns.nspname = :schemaName AND (c.relkind = 'v' OR c.relkind = 'm')
  ORDER BY c.relname
  SQL;
          return $this->db->createCommand($sql, [':schemaName' => $schema])->queryColumn();
      }
docs: {@inheritdoc]