java/pig-galago/src/com/yahoo/pig/BagEvalFunc.java

   1 /*
   2  * Copyright (c) 2007 Yahoo! Inc.  All rights reserved.
   3  * See accompanying LICENSE file.
   4  */
   5 package com.yahoo.pig;
   6
   7 import java.io.IOException;
   8
   9 import com.yahoo.pig.data.*;
  10
  11 /**
  12  * The class is used to implement functions to be applied to
  13  * a dataset. The function is applied to each Tuple in the set.
  14  * The programmer should not make assumptions about state maintained
  15  * between invocations of the invoke() method since the Pig runtime
  16  * will schedule and localize invocations based on information provided
  17  * at runtime.
  18  *
  19  * @author database-systems@yahoo.research
  20  *
  21  */
  22 public abstract class BagEvalFunc extends EvalFunc {
  23
  24     /**
  25      * This callback method must be implemented by all subclasses. This
  26      * is the method that will be invoked on every Tuple of a given dataset.
  27      * Since the dataset may be divided up in a variety of ways the programmer
  28      * should not make assumptions about state that is maintained between
  29      * invocations of this method.
  30      *
  31      * @param input the Tuple to be processed.
  32      * @throws IOException
  33      */
  34     abstract public void exec(Tuple input, DataCollector output) throws IOException;
  35
  36 }