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From Daniel Dai <jiany...@yahoo-inc.com>
Subject Re: Custom UDF + Grouping - Unexpected Output
Date Fri, 10 Dec 2010 00:06:34 GMT
In your udf:
if (num1 < num2)
{
    t.set(0, num1 + "," + num2);
}
else if (num2 < num1)
{
    t.set(0, num2 + "," + num1);
}

You actually only put one item into the tuple. So your UDF generate a 
bag of tuples of one field, not two fields.
I think what you mean is:
if (num1 < num2)
{
    t.set(0, num1);
    t.set(1, num2);
}
else if (num2 < num1)
{
    t.set(0, num2);
    t.set(1, num1);
}

Daniel

Michael Moss wrote:
> Thanks, Daniel.
>
> My UDF with schema (which I suspect is culprit) is below. I've tried
> excluding the "outputSchema()" method entirely and a several variations:
>
> (Full source here: http://pastie.org/1362084)
>
> public class NormalizeListUDF extends EvalFunc<DataBag>
> {
> public DataBag exec(Tuple input) throws IOException
> {
> if (input == null || input.size() == 0)
> return null;
> try
> {
> DataBag output = DefaultBagFactory.getInstance().newDefaultBag();
>
> List<Object> tuples = input.getAll();
> String line = (String) tuples.remove(0);
> line = line.trim();
> String[] items = line.split(",");
>
> for (int i = 1; i < items.length - 1; i++)
> {
> for (int j = i + 1; j < items.length; j++)
> {
> int num1 = Integer.parseInt(items[i]);
> int num2 = Integer.parseInt(items[j]);
>
> Tuple t = TupleFactory.getInstance().newTuple(1);
>
> if (num1 < num2)
> {
> t.set(0, num1 + "," + num2);
> }
> else if (num2 < num1)
> {
> t.set(0, num2 + "," + num1);
> }
> output.add(t);
> }
> }
> return output;
> }
> catch (Exception e)
> {
> throw WrappedIOException.wrap("Caught exception processing input row ", e);
> }
> }
>
> public Schema outputSchema(Schema input)
> {
> try
> {
> List<Schema.FieldSchema> fields = new ArrayList<Schema.FieldSchema>();
> Schema.FieldSchema f1 = new Schema.FieldSchema("f1", DataType.INTEGER);
> Schema.FieldSchema f2 = new Schema.FieldSchema("f2", DataType.INTEGER);
> fields.add(f1);
> fields.add(f2);
>  Schema tupleInner = new Schema(fields);
> Schema.FieldSchema tupleSchema = new Schema.FieldSchema("t1", tupleInner,
> DataType.TUPLE);
>
> Schema bagInner = new Schema(tupleSchema);
> Schema.FieldSchema bagSchema = new Schema.FieldSchema("bag", bagInner,
> DataType.BAG);
> return new Schema(bagSchema);
> }
> catch (Exception e)
> {
> return null;
> }
> }
> }
>
> On Wed, Dec 8, 2010 at 7:04 PM, Daniel Dai <jianyong@yahoo-inc.com> wrote:
>
>   
>> It is not expected. I would think something wrong inside NormalizeListUDF.
>> Make sure you feed bag of tuples which has the schema (int, int) inside your
>> UDF. If you can post your UDF, I can know better.
>>
>> Daniel
>>
>>
>> Michael Moss wrote:
>>
>>     
>>> Hello,
>>>
>>> I'm having an issue with a script that uses an EvalFunc I wrote. The issue
>>> is the final output contains characters that I am not expecting (commas -
>>> followed by what I'm guessing are null fields which I do not see).
>>>
>>> Snippet:
>>> C = FOREACH B GENERATE FLATTEN(B) as (f1:int,f2:int);
>>> grunt> DUMP C;
>>> (2,3)
>>> (2,4)
>>> (2,5)
>>> (3,4)
>>> (3,5)
>>> (4,5)
>>> (2,3)
>>> (2,4)
>>> (2,5)
>>> (3,4)
>>> (3,5)
>>> (4,5)
>>>
>>> D = GROUP C by (f1,f2);
>>> grunt> describe D;
>>> D: {group: (f1: int,f2: int),C: {f1: int,f2: int}}
>>>
>>> grunt> DUMP D;
>>> ((2,3,),{(2,3,),(2,3,)})
>>> ((2,4,),{(2,4,),(2,4,)})
>>> ((2,5,),{(2,5,),(2,5,)})
>>> ((3,4,),{(3,4,),(3,4,)})
>>> ((3,5,),{(3,5,),(3,5,)})
>>> ((4,5,),{(4,5,),(4,5,)})
>>>
>>> My question is, what are these extra comma/null fiends in each tuple? I
>>> expected the first row to read as:
>>> ((2,3),{(2,3),(2,3)})
>>>
>>> It seems related, but when I run 'ILLUSTRATE C', I get an exeption:
>>> java.lang.IndexOutOfBoundsException: Index: 1, Size: 1
>>> at java.util.ArrayList.RangeCheck(ArrayList.java:547)
>>> at java.util.ArrayList.get(ArrayList.java:322)
>>> at org.apache.pig.data.DefaultTuple.get(DefaultTuple.java:143)
>>> at org.apache.pig.pen.util.ExampleTuple.get(ExampleTuple.java:80)
>>> at
>>>
>>> org.apache.pig.pen.util.DisplayExamples.MakeArray(DisplayExamples.java:190)
>>> at
>>>
>>> org.apache.pig.pen.util.DisplayExamples.printTabular(DisplayExamples.java:86)
>>> at
>>>
>>> org.apache.pig.pen.util.DisplayExamples.printTabular(DisplayExamples.java:69)
>>> at
>>> org.apache.pig.pen.ExampleGenerator.getExamples(ExampleGenerator.java:143)
>>> at org.apache.pig.PigServer.getExamples(PigServer.java:785)
>>> at
>>>
>>> org.apache.pig.tools.grunt.GruntParser.processIllustrate(GruntParser.java:555)
>>> at
>>>
>>> org.apache.pig.tools.pigscript.parser.PigScriptParser.parse(PigScriptParser.java:246)
>>> at
>>>
>>> org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:162)
>>> at
>>>
>>> org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:138)
>>> at org.apache.pig.tools.grunt.Grunt.run(Grunt.java:75)
>>> at org.apache.pig.Main.main(Main.java:357)
>>>
>>> Excruciating detail below:
>>>
>>> My script:
>>> REGISTER udf.jar
>>> A = LOAD '/pig_input/co.txt' as (line:chararray);
>>> B = FOREACH A GENERATE com.thumbplay.pig.NormalizeListUDF(line) as B;
>>> C = FOREACH B GENERATE FLATTEN(B) as (f1:int,f2:int);
>>> D = GROUP C by (f1,f2);
>>> E = FOREACH D GENERATE group, COUNT(C);
>>> STORE E INTO 'output' USING PigStorage(',');
>>>
>>> Here's what I'm trying to do:
>>> For input:
>>> A,1,2,3
>>> B,1,2,3
>>>
>>> Produce combinations for each row (My UDF does this):
>>> (1,2),(1,3),(2,3)
>>> (1,2),(1,3),(2,3)
>>>
>>> Flatten them:
>>> (1,2),
>>> (1,3),
>>> (2,3),
>>> (1,2),
>>> (1,3),
>>> (2,3)
>>>
>>> Group and count them:
>>> (1,2),2
>>> (1,3),2
>>> (2,3),2
>>>
>>>
>>>       
>>     


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