datafu.pig.util
Class AssertUDF

java.lang.Object
  org.apache.pig.EvalFunc<java.lang.Boolean>
      org.apache.pig.FilterFunc
          datafu.pig.util.AssertUDF

Direct Known Subclasses:

Assert

public class AssertUDF
extends org.apache.pig.FilterFunc

Filter function which asserts that a value is true.

Unfortunately, the Pig interpreter doesn't recognize boolean expressions nested as function arguments, so this uses C-style booleans. That is, the first argument should be an integer. 0 is interpreted as "false", and anything else is considered "true". The function will cause the Pig script to fail if a "false" value is encountered.

There is a unary and a binary version. The unary version just takes a boolean, and throws out a generic exception message when the assertion is violated. The binary version takes a String as a second argument and throws that out when the assertion is violated.

Example:

 FILTER members BY AssertUDF( (member_id >= 0 ? 1 : 0), 'Doh! Some member ID is negative.' );
 
 

Field Summary

Fields inherited from class org.apache.pig.EvalFunc

log, pigLogger, reporter, returnType

Constructor Summary

AssertUDF()

Method Summary

java.lang.Boolean

exec(org.apache.pig.data.Tuple tuple)

Methods inherited from class org.apache.pig.FilterFunc

finish

Methods inherited from class org.apache.pig.EvalFunc

getArgToFuncMapping, getCacheFiles, getInputSchema, getLogger, getPigLogger, getReporter, getReturnType, getSchemaName, isAsynchronous, outputSchema, 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

AssertUDF

public AssertUDF()

Method Detail

exec

public java.lang.Boolean exec(org.apache.pig.data.Tuple tuple)
                       throws java.io.IOException

Specified by:

exec in class org.apache.pig.EvalFunc<java.lang.Boolean>

Throws:

java.io.IOException