/*
 * 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.spark.sql.sources.v2.reader;

import org.apache.spark.annotation.InterfaceStability;

/**
 * An interface to represent the output data partitioning for a data source, which is returned by
 * {@link SupportsReportPartitioning#outputPartitioning()}. Note that this should work like a
 * snapshot. Once created, it should be deterministic and always report the same number of
 * partitions and the same "satisfy" result for a certain distribution.
 */
@InterfaceStability.Evolving
public interface Partitioning {

  /**
   * Returns the number of partitions(i.e., {@link ReadTask}s) the data source outputs.
   */
  int numPartitions();

  /**
   * Returns true if this partitioning can satisfy the given distribution, which means Spark does
   * not need to shuffle the output data of this data source for some certain operations.
   *
   * Note that, Spark may add new concrete implementations of {@link Distribution} in new releases.
   * This method should be aware of it and always return false for unrecognized distributions. It's
   * recommended to check every Spark new release and support new distributions if possible, to
   * avoid shuffle at Spark side for more cases.
   */
  boolean satisfy(Distribution distribution);
}
