org.apache.hudi.common.data.HoodieListData Maven / Gradle / Ivy

/*
 * 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.hudi.common.data;

import org.apache.hudi.common.function.SerializableFunction;
import org.apache.hudi.common.function.SerializablePairFunction;
import org.apache.hudi.common.util.ValidationUtils;
import org.apache.hudi.common.util.collection.Pair;

import java.util.Iterator;
import java.util.List;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.Function;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

import static org.apache.hudi.common.function.FunctionWrapper.throwingMapToPairWrapper;
import static org.apache.hudi.common.function.FunctionWrapper.throwingMapWrapper;

/**
 * In-memory implementation of {@link HoodieData} holding internally a {@link Stream} of objects.
 *
 * {@link HoodieListData} can have either of the 2 execution semantics:
 *
 * 
 *   Eager: with every operation being executed right away
 *   Lazy: with every operation being "stacked up", with it execution postponed until
 *   "terminal" operation is invoked
 * 
 *
 * NOTE: This is an in-memory counterpart for {@code HoodieJavaRDD}, and it strives to provide
 *       similar semantic as RDD container -- all intermediate (non-terminal, not de-referencing
 *       the stream like "collect", "groupBy", etc) operations are executed *lazily*.
 *       This allows to make sure that compute/memory churn is minimal since only necessary
 *       computations will ultimately be performed.
 *
 *       Please note, however, that while RDD container allows the same collection to be
 *       de-referenced more than once (ie terminal operation invoked more than once),
 *       {@link HoodieListData} allows that only when instantiated w/ an eager execution semantic.
 *
 * @param  type of object.
 */
public class HoodieListData extends HoodieBaseListData implements HoodieData {

  private HoodieListData(List data, boolean lazy) {
    super(data, lazy);
  }

  HoodieListData(Stream dataStream, boolean lazy) {
    super(dataStream, lazy);
  }

  /**
   * Creates instance of {@link HoodieListData} bearing *eager* execution semantic
   *
   * @param listData a {@link List} of objects in type T
   * @param       type of object
   * @return a new instance containing the {@link List} reference
   */
  public static  HoodieListData eager(List listData) {
    return new HoodieListData<>(listData, false);
  }

  /**
   * Creates instance of {@link HoodieListData} bearing *lazy* execution semantic
   *
   * @param listData a {@link List} of objects in type T
   * @param       type of object
   * @return a new instance containing the {@link List} reference
   */
  public static  HoodieListData lazy(List listData) {
    return new HoodieListData<>(listData, true);
  }

  @Override
  public void persist(String level) {
    // No OP
  }

  @Override
  public void unpersist() {
    // No OP
  }

  @Override
  public  HoodieData map(SerializableFunction func) {
    return new HoodieListData<>(asStream().map(throwingMapWrapper(func)), lazy);
  }

  @Override
  public  HoodieData mapPartitions(SerializableFunction, Iterator> func, boolean preservesPartitioning) {
    Function, Iterator> mapper = throwingMapWrapper(func);
    return new HoodieListData<>(
        StreamSupport.stream(
            Spliterators.spliteratorUnknownSize(
                mapper.apply(asStream().iterator()), Spliterator.ORDERED), true),
        lazy
    );
  }

  @Override
  public  HoodieData flatMap(SerializableFunction> func) {
    Function> mapper = throwingMapWrapper(func);
    Stream mappedStream = asStream().flatMap(e ->
        StreamSupport.stream(
            Spliterators.spliteratorUnknownSize(mapper.apply(e), Spliterator.ORDERED), true));
    return new HoodieListData<>(mappedStream, lazy);
  }

  @Override
  public  HoodiePairData flatMapToPair(SerializableFunction>> func) {
    Function>> mapper = throwingMapWrapper(func);
    Stream> mappedStream = asStream().flatMap(e ->
        StreamSupport.stream(
            Spliterators.spliteratorUnknownSize(mapper.apply(e), Spliterator.ORDERED), true));

    return new HoodieListPairData<>(mappedStream, lazy);
  }

  @Override
  public  HoodiePairData mapToPair(SerializablePairFunction func) {
    Function> throwableMapToPairFunc = throwingMapToPairWrapper(func);
    return new HoodieListPairData<>(asStream().map(throwableMapToPairFunc), lazy);
  }

  @Override
  public HoodieData distinct() {
    return new HoodieListData<>(asStream().distinct(), lazy);
  }

  @Override
  public HoodieData distinct(int parallelism) {
    return distinct();
  }

  @Override
  public  HoodieData distinctWithKey(SerializableFunction keyGetter, int parallelism) {
    return mapToPair(i -> Pair.of(keyGetter.apply(i), i))
        .reduceByKey((value1, value2) -> value1, parallelism)
        .values();
  }

  @Override
  public HoodieData filter(SerializableFunction filterFunc) {
    return new HoodieListData<>(asStream().filter(r -> throwingMapWrapper(filterFunc).apply(r)), lazy);
  }

  @Override
  public HoodieData union(HoodieData other) {
    ValidationUtils.checkArgument(other instanceof HoodieListData);
    return new HoodieListData<>(Stream.concat(asStream(), ((HoodieListData)other).asStream()), lazy);
  }

  @Override
  public HoodieData repartition(int parallelism) {
    // no op
    return this;
  }

  @Override
  public boolean isEmpty() {
    return super.isEmpty();
  }

  @Override
  public long count() {
    return super.count();
  }

  @Override
  public int getNumPartitions() {
    return 1;
  }

  @Override
  public List collectAsList() {
    return super.collectAsList();
  }
}