code: function FilteredPoolCluster(poolCluster, patternArg, selectorArg) {
    const cluster = poolCluster;
    const pattern = patternArg;
    const selector = selectorArg;
  
    /**
     * Get a connection according to previously indicated pattern and selector.
     *
     * @return {Promise}
     */
    this.getConnection = () => {
      return cluster.getConnection(pattern, selector);
    };
  
    /**
     * Execute a query on one connection from available pools matching pattern
     * in cluster.
     *
     * @param sql   sql command
     * @param value parameter value of sql command (not mandatory)
     * @return {Promise}
     */
    this.query = function(sql, value) {
      return cluster
        .getConnection(pattern, selector)
        .then(conn => {
          return conn
            .query(sql, value)
            .then(res => {
              conn.end();
              return res;
            })
            .catch(err => {
              conn.end();
              return Promise.reject(err);
            });
        })
        .catch(err => {
          return Promise.reject(err);
        });
    };
  
    /**
     * Execute a batch on one connection from available pools matching pattern
     * in cluster.
     *
     * @param sql   sql command
     * @param value parameter value of sql command
     * @return {Promise}
     */
    this.batch = function(sql, value) {
      return cluster
        .getConnection(pattern, selector)
        .then(conn => {
          return conn
            .batch(sql, value)
            .then(res => {
              conn.end();
              return res;
            })
            .catch(err => {
              conn.end();
              return Promise.reject(err);
            });
        })
        .catch(err => {
          return Promise.reject(err);
        });
    };
  }
docs: Similar to pool cluster with pre-set pattern and selector.
  Additional method query
  
  @param poolCluster    cluster
  @param patternArg     pre-set pattern
  @param selectorArg    pre-set selector
  @constructor