src/main/java/org/apache/datasketches/pig/frequencies/UnionFrequentItemsSketch.java

/*
 * 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.datasketches.pig.frequencies;

import java.io.IOException;

import org.apache.datasketches.ArrayOfItemsSerDe;
import org.apache.datasketches.frequencies.ItemsSketch;
import org.apache.log4j.Logger;
import org.apache.pig.Accumulator;
import org.apache.pig.EvalFunc;
import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.data.DataBag;
import org.apache.pig.data.Tuple;

/**
 * This is a generic implementation to be specialized in concrete UDFs
 * @param <T> Type of item
 */
public abstract class UnionFrequentItemsSketch<T> extends EvalFunc<Tuple> implements Accumulator<Tuple> {
  private final int sketchSize_;
  private final ArrayOfItemsSerDe<T> serDe_;
  private ItemsSketch<T> sketch_;
  private boolean isFirstCall_ = true;

  /**
   * Constructs a function given a sketch size and serde
   * @param sketchSize parameter controlling the size of the sketch and the accuracy
   * @param serDe an instance of ArrayOfItemsSerDe to serialize and deserialize arrays of items
   */
  public UnionFrequentItemsSketch(final int sketchSize, final ArrayOfItemsSerDe<T> serDe) {
    super();
    sketchSize_ = sketchSize;
    serDe_ = serDe;
  }

  @Override
  public Tuple exec(final Tuple inputTuple) throws IOException {
    if (isFirstCall_) {
      // this is to see in the log which way was used by Pig
      Logger.getLogger(getClass()).info("exec is used");
      isFirstCall_ = false;
    }
    if ((inputTuple == null) || (inputTuple.size() == 0)) {
      return null;
    }
    accumulate(inputTuple);
    final Tuple outputTuple = getValue();
    cleanup();
    return outputTuple;
  }

  @Override
  public void accumulate(final Tuple inputTuple) throws IOException {
    if (isFirstCall_) {
      // this is to see in the log which way was used by Pig
      Logger.getLogger(getClass()).info("accumulator is used");
      isFirstCall_ = false;
    }
    if ((inputTuple == null) || (inputTuple.size() != 1)) {
      return;
    }
    final Object obj = inputTuple.get(0);
    if (!(obj instanceof DataBag)) {
      return;
    }
    final DataBag bag = (DataBag) inputTuple.get(0);
    if (bag.size() == 0) {
      return;
    }

    if (sketch_ == null) {
      sketch_ = new ItemsSketch<T>(sketchSize_);
    }
    for (final Tuple innerTuple: bag) {
      final int sz = innerTuple.size();
      if ((sz != 1) || (innerTuple.get(0) == null)) {
        continue;
      }
      final ItemsSketch<T> incomingSketch = Util.deserializeSketchFromTuple(innerTuple, serDe_);
      sketch_.merge(incomingSketch);
    }
  }

  @Override
  public Tuple getValue() {
    if (sketch_ == null) { //return an empty sketch
      try {
        return Util.serializeSketchToTuple(new ItemsSketch<T>(sketchSize_), serDe_);
      } catch (final ExecException ex) {
        throw new RuntimeException("Pig Error: " + ex.getMessage(), ex);
      }
    }

    try {
      return Util.serializeSketchToTuple(sketch_, serDe_);
    } catch (final ExecException ex) {
      throw new RuntimeException("Pig Error: " + ex.getMessage(), ex);
    }
  }

  @Override
  public void cleanup() {
    if (sketch_ != null) {
      sketch_.reset();
    }
  }

}