com.hazelcast.org.apache.calcite.adapter.enumerable.LazyAggregateLambdaFactory Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of hazelcast-sql Show documentation
SQL Parser and Optimizer
There is a newer version: 5.4.0
/*
 * 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 com.hazelcast.com.liance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.com.hazelcast.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.hazelcast.org.apache.calcite.adapter.enumerable;

import com.hazelcast.org.apache.calcite.linq4j.function.Function0;
import com.hazelcast.org.apache.calcite.linq4j.function.Function1;
import com.hazelcast.org.apache.calcite.linq4j.function.Function2;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * Generate aggregate lambdas that preserve the input source before calling each
 * aggregate adder, this implementation is generally used when we need to sort the input
 * before performing aggregation.
 *
 * @param  Type of the enumerable input source
 * @param  Type of the group-by key
 * @param  Type of the original accumulator
 * @param  Type of the enumerable output result
 */
public class LazyAggregateLambdaFactory
    implements AggregateLambdaFactory, TResult, TKey> {

  private final Function0 accumulatorInitializer;
  private final List> accumulators;

  public LazyAggregateLambdaFactory(
      Function0 accumulatorInitializer,
      List> accumulators) {
    this.accumulatorInitializer = accumulatorInitializer;
    this.accumulators = accumulators;
  }

  public Function0> accumulatorInitializer() {
    return LazySource::new;
  }

  public Function2,
      TSource, LazySource> accumulatorAdder() {
    return (lazySource, source) -> {
      lazySource.add(source);
      return lazySource;
    };
  }

  public Function1, TResult> singleGroupResultSelector(
      Function1 resultSelector) {
    return lazySource -> {
      final TOrigAccumulate accumulator = accumulatorInitializer.apply();
      for (LazyAccumulator acc : accumulators) {
        acc.accumulate(lazySource, accumulator);
      }
      return resultSelector.apply(accumulator);
    };
  }

  public Function2, TResult> resultSelector(
      Function2 resultSelector) {
    return (groupByKey, lazySource) -> {
      final TOrigAccumulate accumulator = accumulatorInitializer.apply();
      for (LazyAccumulator acc : accumulators) {
        acc.accumulate(lazySource, accumulator);
      }
      return resultSelector.apply(groupByKey, accumulator);
    };
  }

  /**
   * Cache the input sources. (Will be aggregated in result selector.)
   *
   * @param  Type of the enumerable input source.
   */
  public static class LazySource implements Iterable {
    private final List list = new ArrayList<>();

    private void add(TSource source) {
      list.add(source);
    }

    @Override public Iterator iterator() {
      return list.iterator();
    }
  }

  /**
   * Accumulate on the cached input sources.
   *
   * @param  Type of the original accumulator
   * @param  Type of the enumerable input source.
   */
  public interface LazyAccumulator {
    void accumulate(Iterable sourceIterable, TOrigAccumulate accumulator);
  }
}