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From "Viraj Bhat (JIRA)" <j...@apache.org>
Subject [jira] Created: (PIG-546) FilterFunc calls empty constructor when it should be calling parameterized constructor
Date Thu, 27 Nov 2008 02:42:44 GMT
FilterFunc calls empty constructor when it should be calling parameterized constructor
--------------------------------------------------------------------------------------

                 Key: PIG-546
                 URL: https://issues.apache.org/jira/browse/PIG-546
             Project: Pig
          Issue Type: Bug
          Components: impl
    Affects Versions: types_branch
            Reporter: Viraj Bhat
             Fix For: types_branch


The following piece of Pig Script uses a custom UDF known as FILTERFROMFILE which extends
the FilterFunc. It contains two constructors, an empty constructor which is mandatory and
the parameterized constructor. The parameterized constructor  passes the HDFS filename, which
the exec function uses to construct a HashMap. The HashMap is later used for filtering records
based on the match criteria in the HDFS file.
{code}
register util.jar;
--util.jar contains the FILTERFROMFILE class

define FILTER_CRITERION util.FILTERFROMFILE('/user/viraj/insetfilterfile');

RAW_LOGS = load 'mydata.txt' as (url:chararray, numvisits:int);

FILTERED_LOGS = filter RAW_LOGS by FILTER_CRITERION(numvisits);

dump FILTERED_LOGS;
{code}

When you execute the above script,  it results in a single Map only job with 1 Map. It seems
that the empty constructor is called 5 times, and ultimately results in failure of the job.
===========================================
parameterized constructor: /user/viraj/insetfilterfile
parameterized constructor: /user/viraj/insetfilterfile
empty constructor
empty constructor
empty constructor
empty constructor
empty constructor
===========================================
Error in the Hadoop backend
===========================================
java.lang.IllegalArgumentException: Can not create a Path from an empty string
	at org.apache.hadoop.fs.Path.checkPathArg(Path.java:82)
	at org.apache.hadoop.fs.Path.(Path.java:90)
	at org.apache.pig.backend.hadoop.datastorage.HDataStorage.isContainer(HDataStorage.java:199)
	at org.apache.pig.backend.hadoop.datastorage.HDataStorage.asElement(HDataStorage.java:130)
	at org.apache.pig.impl.io.FileLocalizer.openDFSFile(FileLocalizer.java:164)
	at util.FILTERFROMFILE.init(FILTERFROMFILE.java:70)
	at util.FILTERFROMFILE.exec(FILTERFROMFILE.java:89)
	at util.FILTERFROMFILE.exec(FILTERFROMFILE.java:52)
	at org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.getNext(POUserFunc.java:179)
	at org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.getNext(POUserFunc.java:217)
	at org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POFilter.getNext(POFilter.java:148)
	at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapBase.runPipeline(PigMapBase.java:170)
	at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapBase.map(PigMapBase.java:158)
	at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapOnly$Map.map(PigMapOnly.java:65)
	at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:47)
	at org.apache.hadoop.mapred.MapTask.run(MapTask.java:227)
	at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2209)
===========================================
Attaching the sample data and the filter function UDF.

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