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 com.datastax.dse.driver.api.core.cql.reactive;
  
  import com.datastax.oss.driver.api.core.cql.ColumnDefinitions;
  import com.datastax.oss.driver.api.core.cql.ExecutionInfo;
  import edu.umd.cs.findbugs.annotations.NonNull;
  import org.reactivestreams.Publisher;
  
  /**
   * Interface implemented by all the reactive result set publishers provided by the driver, and
   * notably by {@link ReactiveResultSet}.
   */
  public interface ReactiveQueryMetadata {
  
    /**
     * Returns metadata about the {@linkplain ColumnDefinitions columns} contained in this result set.
     *
     * <p>This publisher emits exactly one item as soon as the first response arrives, then completes.
     * If the query execution fails <em>within the first request-response cycle</em>, then this
     * publisher will fail with the same error; however if the error happens <em>after the first
     * response</em>, then this publisher will be already completed and will not acknowledge that
     * error in any way.
     *
     * <p>By default, publishers returned by this method do not support multiple subscriptions.
     *
     * @see ReactiveRow#getColumnDefinitions()
     */
    @NonNull
    Publisher<? extends ColumnDefinitions> getColumnDefinitions();
  
    /**
     * Returns {@linkplain ExecutionInfo information about the execution} of all requests that have
     * been performed so far to assemble this result set.
     *
     * <p>If the query is not paged, this publisher will emit exactly one item as soon as the response
     * arrives, then complete. If the query is paged, it will emit multiple items, one per page; then
     * it will complete when the last page arrives. If the query execution fails, then this publisher
     * will fail with the same error.
     *
     * <p>By default, publishers returned by this method do not support multiple subscriptions.
     *
     * @see ReactiveRow#getExecutionInfo()
     */
    @NonNull
    Publisher<? extends ExecutionInfo> getExecutionInfos();
  
    /**
     * If the query that produced this result was a conditional update, indicates whether it was
     * successfully applied.
     *
     * <p>This publisher emits exactly one item as soon as the first response arrives, then completes.
     * If the query execution fails <em>within the first request-response cycle</em>, then this
     * publisher will fail with the same error; however if the error happens <em>after the first
     * response</em>, then this publisher will be already completed and will not acknowledge that
     * error in any way.
     *
     * <p>By default, publishers returned by this method do not support multiple subscriptions.
     *
     * <p>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.
     *
     * <p>Note that, for versions of Cassandra strictly lower than 2.1.0-rc2, a server-side bug (<a
     * href="https://issues.apache.org/jira/browse/CASSANDRA-7337">CASSANDRA-7337</a>) causes this
     * method to always return {@code true} for batches containing conditional queries.
     *
     * @see ReactiveRow#wasApplied()
     */
    @NonNull
    Publisher<Boolean> wasApplied();
  }
  