content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 org.apache.cassandra.distributed.api;
  
  import java.util.Iterator;
  import java.util.List;
  import java.util.function.Function;
  import java.util.function.Predicate;
  
  /**
   * A table of data representing a complete query result.
   * <p>
   * A <code>QueryResult</code> is different from {@link java.sql.ResultSet} in several key ways:
   *
   * <ul>
   *     <li>represents a complete result rather than a cursor</li>
   *     <li>returns a {@link Row} to access the current row of data</li>
   *     <li>relies on object pooling; {@link #hasNext()} may return the same object just with different data, accessing a
   *     {@link Row} from a previous {@link #hasNext()} call has undefined behavior.</li>
   *     <li>includes {@link #filter(Predicate)}, this will do client side filtering since Apache Cassandra is more
   *     restrictive on server side filtering</li>
   * </ul>
   *
   * <h2>Unsafe patterns</h2>
   * <p>
   * Below are a few unsafe patterns which may lead to unexpected results
   *
   * <code>{@code
   * while (rs.hasNext()) {
   *   list.add(rs.next());
   * }
   * }</code>
   *
   * <code>{@code
   * rs.forEach(list::add)
   * }</code>
   * <p>
   * Both cases have the same issue; reference to a row from a previous call to {@link #hasNext()}.  Since the same {@link Row}
   * object can be used across different calls to {@link #hasNext()} this would mean any attempt to access after the fact
   * points to newer data.  If this behavior is not desirable and access is needed between calls, then {@link Row#copy()}
   * should be used; this will clone the {@link Row} and return a new object pointing to the same data.
   */
  public interface QueryResult extends Iterator<Row>
  {
      List<String> names();
      
      List<String> warnings();
  
      default QueryResult filter(Predicate<Row> fn)
      {
          return QueryResults.filter(this, fn);
      }
  
      default <A> Iterator<A> map(Function<? super Row, ? extends A> fn)
      {
          return new Iterator<A>()
          {
              @Override
              public boolean hasNext()
              {
                  return QueryResult.this.hasNext();
              }
  
              @Override
              public A next()
              {
                  return fn.apply(QueryResult.this.next());
              }
          };
      }
  }
  