com.datastax.driver.core.ResultSet Maven / Gradle / Ivy

/*
 * Copyright DataStax, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.datastax.driver.core;

/**
 * The result of a query.
 *
 * The retrieval of the rows of a ResultSet is generally paged (a first page of result is fetched
 * and the next one is only fetched once all the results of the first one has been consumed). The
 * size of the pages can be configured either globally through {@link QueryOptions#setFetchSize} or
 * per-statement with {@link Statement#setFetchSize}. Though new pages are automatically (and
 * transparently) fetched when needed, it is possible to force the retrieval of the next page early
 * through {@link #fetchMoreResults}. Please note however that this ResultSet paging is not
 * available with the version 1 of the native protocol (i.e. with Cassandra 1.2 or if version 1 has
 * been explicitly requested through {@link Cluster.Builder#withProtocolVersion}). If the protocol
 * version 1 is in use, a ResultSet is always fetched in it's entirely and it's up to the client to
 * make sure that no query can yield ResultSet that won't hold in memory.
 *
 * 
Note that this class is not thread-safe.
 */
public interface ResultSet extends PagingIterable {

  // redeclared only to make clirr happy
  @Override
  Row one();

  /**
   * Returns the columns returned in this ResultSet.
   *
   * @return the columns returned in this ResultSet.
   */
  public ColumnDefinitions getColumnDefinitions();

  /**
   * If the query that produced this ResultSet was a conditional update, return whether it was
   * successfully applied.
   *
   * 
This is equivalent to calling:
   *
   * 

   *
   * 
   * rs.one().getBool("[applied]");
   * 
   *
   * Except that this method peeks at the next row without consuming it.
   *
   * For consistency, this method always returns {@code true} for non-conditional queries
   * (although there is no reason to call the method in that case). This is also the case for
   * conditional DDL statements ({@code CREATE KEYSPACE... IF NOT EXISTS}, {@code CREATE TABLE... IF
   * NOT EXISTS}), for which Cassandra doesn't return an {@code [applied]} column.
   *
   * Note that, for versions of Cassandra strictly lower than 2.0.9 and 2.1.0-rc2, a server-side
   * bug (CASSANDRA-7337) causes this method to always return {@code true} for batches containing
   * conditional queries.
   *
   * @return if the query was a conditional update, whether it was applied. {@code true} for other
   *     types of queries.
   * @see CASSANDRA-7337
   */
  public boolean wasApplied();
}