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Data Sketches Pig
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/*
 * Copyright 2019, Verizon Media.
 * Licensed under the terms of the Apache License 2.0. See LICENSE file at the project root for terms.
 */

package com.yahoo.sketches.pig.cpc;

import static com.yahoo.sketches.Util.DEFAULT_UPDATE_SEED;

import java.io.IOException;

import org.apache.log4j.Logger;
import org.apache.pig.Accumulator;
import org.apache.pig.Algebraic;
import org.apache.pig.EvalFunc;
import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.data.DataBag;
import org.apache.pig.data.DataByteArray;
import org.apache.pig.data.DataType;
import org.apache.pig.data.Tuple;

import com.yahoo.sketches.cpc.CpcSketch;

/**
 * This is a Pig UDF that builds sketches from data.
 * This class implements both the Accumulator and Algebraic interfaces.
 *
 * @author Alexander Saydakov
 */
public class DataToSketch extends EvalFunc implements Accumulator, Algebraic {

  private DataByteArray emptySketch_; // this is to cash an empty sketch

  private final int lgK_;
  private final long seed_;
  private CpcSketch accumSketch_;
  private boolean isFirstCall_; // for logging

  /**
   * Constructor with default lgK and seed
   */
  public DataToSketch() {
    this(CpcSketch.DEFAULT_LG_K, DEFAULT_UPDATE_SEED);
  }

  /**
   * Constructor with given lgK as string and default seed
   *
   * @param lgK in a form of a String
   */
  public DataToSketch(final String lgK) {
    this(Integer.parseInt(lgK), DEFAULT_UPDATE_SEED);
  }

  /**
   * Constructor with given lgK and seed as strings
   *
   * @param lgK in a form of a String
   * @param seed in a form of a String
   */
  public DataToSketch(final String lgK, final String seed) {
    this(Integer.parseInt(lgK), Long.parseLong(seed));
  }

  /**
   * Base constructor.
   *
   * @param lgK parameter controlling the sketch size and accuracy
   * @param seed parameter to use during hashing
   */
  public DataToSketch(final int lgK, final long seed) {
    super();
    lgK_ = lgK;
    seed_ = seed;
  }

  /**
   * Top-level exec function.
   * This method accepts an input Tuple containing a Bag of one or more inner Datum Tuples
   * and returns a single serialized CpcSketch as a DataByteArray.
   *
   * Datum Tuple is a Tuple containing a single field, which can be one of the following
   * (Java type: Pig type):
   * 
   *   Byte: BYTE
   *   Integer: INTEGER
   *   Long: LONG
   *   Float: FLOAT
   *   Double: DOUBLE
   *   String: CHARARRAY
   *   DataByteArray: BYTEARRAY
   * 
   *
   * @param inputTuple A tuple containing a single bag, containing Datum Tuples.
   * @return serialized CpcSketch
   * @see "org.apache.pig.EvalFunc.exec(org.apache.pig.data.Tuple)"
   * @throws IOException from Pig
   */

  @Override
  public DataByteArray exec(final Tuple inputTuple) throws IOException {
    if (isFirstCall_) {
      Logger.getLogger(getClass()).info("Exec was used");
      isFirstCall_ = false;
    }
    if (inputTuple == null || inputTuple.size() == 0) {
      if (emptySketch_ == null) {
        emptySketch_ = new DataByteArray(new CpcSketch(lgK_, seed_).toByteArray());
      }
      return emptySketch_;
    }
    final CpcSketch sketch = new CpcSketch(lgK_, seed_);
    final DataBag bag = (DataBag) inputTuple.get(0);
    updateSketch(bag, sketch);
    return new DataByteArray(sketch.toByteArray());
  }

  /**
   * An Accumulator version of the standard exec() method. Like exec(),
   * accumulator is called with a bag of Datum Tuples. Unlike exec(), it doesn't serialize the
   * result at the end. Instead, it can be called multiple times, each time with another bag of
   * Datum Tuples to be input to the sketch.
   *
   * @param inputTuple A tuple containing a single bag, containing Datum Tuples.
   * @see #exec
   * @see "org.apache.pig.Accumulator.accumulate(org.apache.pig.data.Tuple)"
   * @throws IOException by Pig
   */
  @Override
  public void accumulate(final Tuple inputTuple) throws IOException {
    if (isFirstCall_) {
      Logger.getLogger(getClass()).info("Accumulator was used");
      isFirstCall_ = false;
    }
    if (inputTuple == null || inputTuple.size() == 0) { return; }
    final DataBag bag = (DataBag) inputTuple.get(0);
    if (bag == null) { return; }
    if (accumSketch_ == null) {
      accumSketch_ = new CpcSketch(lgK_);
    }
    updateSketch(bag, accumSketch_);
  }

  /**
   * Returns the sketch that has been built up by multiple calls to {@link #accumulate}.
   *
   * @return serialized CpcSketch
   * @see "org.apache.pig.Accumulator.getValue()"
   */
  @Override
  public DataByteArray getValue() {
    if (accumSketch_ == null) {
      if (emptySketch_ == null) {
        emptySketch_ = new DataByteArray(new CpcSketch(lgK_, seed_).toByteArray());
      }
      return emptySketch_;
    }
    return new DataByteArray(accumSketch_.toByteArray());
  }

  /**
   * Cleans up the UDF state after being called using the {@link Accumulator} interface.
   *
   * @see "org.apache.pig.Accumulator.cleanup()"
   */
  @Override
  public void cleanup() {
    accumSketch_ = null;
  }

  @Override
  public String getInitial() {
    return AlgebraicInitial.class.getName();
  }

  @Override
  public String getIntermed() {
    return DataToSketchAlgebraicIntermediate.class.getName();
  }

  @Override
  public String getFinal() {
    return DataToSketchAlgebraicFinal.class.getName();
  }

  static void updateSketch(final DataBag bag, final CpcSketch sketch) throws ExecException {
    // bag is not empty, process each innerTuple in the bag
    for (final Tuple innerTuple: bag) {
      final Object f0 = innerTuple.get(0); // consider only field 0
      if (f0 == null) {
        continue;
      }
      final byte type = innerTuple.getType(0);

      switch (type) {
        case DataType.NULL:
          break;
        case DataType.BYTE:
          sketch.update((byte) f0);
          break;
        case DataType.INTEGER:
          sketch.update((int) f0);
          break;
        case DataType.LONG:
          sketch.update((long) f0);
          break;
        case DataType.FLOAT:
          sketch.update((float) f0);
          break;
        case DataType.DOUBLE:
          sketch.update((double) f0);
          break;
        case DataType.BYTEARRAY: {
          final DataByteArray dba = (DataByteArray) f0;
          sketch.update(dba.get());
          break;
        }
        case DataType.CHARARRAY: {
          final String str = (String) f0;
          // conversion to char[] avoids costly UTF-8 encoding
          sketch.update(str.toCharArray());
          break;
        }
        default:
          throw new IllegalArgumentException("Field 0 of innerTuple must be one of "
              + "NULL, BYTE, INTEGER, LONG, FLOAT, DOUBLE, BYTEARRAY or CHARARRAY. "
              + "Given Type = " + DataType.findTypeName(type)
              + ", Object = " + f0.toString());
      }
    }
  }

}