datafu.pig.sets

Class SetDifference

java.lang.Object

org.apache.pig.EvalFunc<org.apache.pig.data.DataBag>

datafu.pig.sets.SetOperationsBase

datafu.pig.sets.SetDifference

public class SetDifference
extends SetOperationsBase

Computes the set difference of two or more bags. Duplicates are eliminated. The input bags must be sorted.

If bags A and B are provided, then this computes A-B, i.e. all elements in A that are not in B. If bags A, B and C are provided, then this computes A-B-C, i.e. all elements in A that are not in B or C.

Example:

 
 define SetDifference datafu.pig.sets.SetDifference();

 -- input:
 -- ({(1),(2),(3),(4),(5),(6)},{(3),(4)})
 input = LOAD 'input' AS (B1:bag{T:tuple(val:int)},B2:bag{T:tuple(val:int)});

 input = FOREACH input {
   B1 = ORDER B1 BY val ASC;
   B2 = ORDER B2 BY val ASC;

   -- output:
   -- ({(1),(2),(5),(6)})
   GENERATE SetDifference(B1,B2);
 }
 

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.pig.EvalFunc

org.apache.pig.EvalFunc.SchemaType

Field Summary

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

Constructors

Constructor and Description
SetDifference()

Method Summary

Modifier and Type	Method and Description
int	countMatches(java.util.PriorityQueue<datafu.pig.sets.SetDifference.Pair> pq) Counts how many elements in the priority queue match the element at the front of the queue, which should be from the first bag.
org.apache.pig.data.DataBag	exec(org.apache.pig.data.Tuple input)

Methods inherited from class datafu.pig.sets.SetOperationsBase

outputSchema

Methods inherited from class org.apache.pig.EvalFunc

allowCompileTimeCalculation, finish, getArgToFuncMapping, getCacheFiles, getInputSchema, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, getShipFiles, isAsynchronous, progress, setInputSchema, setPigLogger, setReporter, setUDFContextSignature, warn

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SetDifference

public SetDifference()

Method Detail

countMatches

public int countMatches(java.util.PriorityQueue<datafu.pig.sets.SetDifference.Pair> pq)

Counts how many elements in the priority queue match the element at the front of the queue, which should be from the first bag.

Parameters:

pq - priority queue

Returns:

number of matches

exec

public org.apache.pig.data.DataBag exec(org.apache.pig.data.Tuple input)
                                 throws java.io.IOException

Specified by:

exec in class org.apache.pig.EvalFunc<org.apache.pig.data.DataBag>

Throws:

java.io.IOException