org.apache.pig.builtin

Class SUBTRACT

java.lang.Object

org.apache.pig.EvalFunc<DataBag>

org.apache.pig.builtin.SUBTRACT

public class SUBTRACT
extends EvalFunc<DataBag>

SUBTRACT takes two bags as arguments and returns a new bag composed of tuples of first bag not in the second bag.
If null, bag arguments are replaced by empty bags.

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
SUBTRACT()

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 the two bag fields from input Tuple and returns a new bag composed of elements of first bag not in the second bag.

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

SUBTRACT

public SUBTRACT()

Method Detail

exec

public DataBag exec(Tuple input)
             throws java.io.IOException

Compares the two bag fields from input Tuple and returns a new bag composed of elements of first bag not in the second bag.

Specified by:

exec in class EvalFunc<DataBag>

Parameters:

input - a tuple with exactly two bag fields.

Returns:

result, of type T.

Throws:

java.io.IOException - if there are not exactly two fields in a tuple or if they are not DataBag.

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