org.apache.pig.builtin

Class DIFF

java.lang.Object

org.apache.pig.EvalFunc<DataBag>

org.apache.pig.builtin.DIFF

public class DIFF
extends EvalFunc<DataBag>

DIFF takes two bags as arguments and compares them. Any tuples that are in one bag but not the other are returned. If the fields are not bags then they will be returned if they do not match, or an empty bag will be returned if the two records match.

The implementation assumes that both bags being passed to this function will fit entirely into memory simultaneously. If that is not the case the UDF will still function, but it will be very slow.

Nested Class Summary

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

EvalFunc.SchemaType

Field Summary

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

Constructors

Constructor and Description
DIFF()

Method Summary

Modifier and Type	Method and Description
boolean	allowCompileTimeCalculation() Whether the UDF should be evaluated at compile time if all inputs are constant.
DataBag	exec(Tuple input) Compares a tuple with two fields.

Methods inherited from class org.apache.pig.EvalFunc

finish, getArgToFuncMapping, getCacheFiles, getInputSchema, getLoadCaster, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, getSchemaType, getShipFiles, isAsynchronous, needEndOfAllInputProcessing, outputSchema, progress, setEndOfAllInput, 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

DIFF

public DIFF()

Method Detail

exec

public DataBag exec(Tuple input)
             throws IOException

Compares a tuple with two fields. Emits any differences.

Specified by:

exec in class EvalFunc<DataBag>

Parameters:

input - a tuple with exactly two fields.

Returns:

result, of type T.

Throws:

IOException - if there are not exactly two fields in a tuple

allowCompileTimeCalculation

public boolean allowCompileTimeCalculation()

Description copied from class: EvalFunc

Whether the UDF should be evaluated at compile time if all inputs are constant. This is applicable for most UDF, however, if a UDF will access hdfs file which is not available at compile time, it has to be false

Overrides:

allowCompileTimeCalculation in class EvalFunc<DataBag>

Returns:

Whether or not compile time calculation is allowed, default to false to ensure legacy UDF will get the right behavior