UDAF on AWS Hive

[Matthew Bryan]

I'm writing a basic group_concat UDAF for the Amazon version of
Hive....and it's working fine for unordered groupings. But I can't
seem to get an ordered version working (filling an array based on an
IntWritable passed alongside). When I move from using Text return type
on terminatePartial() to either Text[] or a State class I start
getting errors:

FAILED: Error in semantic analysis:
org.apache.hadoop.hive.ql.metadata.HiveException: Cannot recognize
return type class [Lorg.apache.hadoop.io.Text; from public
org.apache.hadoop.io.Text[]
com.company.hadoop.hive.udaf.UDAFGroupConcatN$GroupConcatNStringEvaluator.terminatePartial()

or

FAILED: Error in semantic analysis:
org.apache.hadoop.hive.ql.metadata.HiveException: Cannot recognize
return type class
com.company.hadoop.hive.udaf.UDAFGroupConcatN$UDAFGroupConc
atNState from public
com.company.hadoop.hive.udaf.UDAFGroupConcatN$UDAFGroupConcatNState
com.company.hadoop.hive.udaf.UDAFGroupConcatN$GroupConcatNStringEvaluator.terminatePartial
()

What limits are there on the return type of
terminatePartial()....shouldn't it just have to match the argument of
merge and nothing more? Keep in mind this is the Amazon version of
Hive (0.4 I think)....

I put both versions of the UDAF below, ordered and unordered.

Thanks for your time.

Matt


######### Working Unordered ############
/*QUERY: select user, event, group_concat(details) from datatable
group by user,event;*/

package com.company.hadoop.hive.udaf;

import org.apache.hadoop.hive.ql.exec.UDAF;
import org.apache.hadoop.hive.ql.exec.UDAFEvaluator;
import org.apache.hadoop.io.Text;

public class UDAFGroupConcat extends UDAF{

        public static class GroupConcatStringEvaluator implements
UDAFEvaluator {
                private Text mOutput;
                private boolean mEmpty;

        public GroupConcatStringEvaluator() {
                super();
                init();
        }

        public void init() {
                mOutput = null;
                mEmpty = true;
        }

        public boolean iterate(Text o) {
                if (o!=null) {
                        if(mEmpty) {
                                mOutput = new Text(o);
                                mEmpty = false;
                        } else {
                                mOutput.set(mOutput.toString()+"
"+o.toString());
                        }
                }
                return true;
        }
        public Text terminatePartial() {return mEmpty ? null : mOutput;}
        public boolean merge(Text o) {return iterate(o);}
        public Text terminate() {return mEmpty ? null : mOutput;}
}
}

############ Not Working Ordered #############
/*QUERY: select user, event, group_concatN(details, detail_id) from
datatable group by user,event;*/

package com.company.hadoop.hive.udaf;

import org.apache.hadoop.hive.ql.exec.UDAF;
import org.apache.hadoop.hive.ql.exec.UDAFEvaluator;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.IntWritable;

public class UDAFGroupConcatN extends UDAF{

        public static class GroupConcatNStringEvaluator implements
UDAFEvaluator {

                private Text[] mArray;
                private boolean mEmpty;

                public GroupConcatNStringEvaluator() {
                        super();
                        init();
                }

        public void init() {
                mArray = new Text[5];
                mEmpty = true;
        }

        public boolean iterate(Text o, IntWritable N) {
                if (o!=null&&N!=null) {
                        mArray[N.get()].set(o.toString());
                        mEmpty=false;
                }
                return true;
        }
        public Text[] terminatePartial() {return mEmpty ? null : mArray;}
        public boolean merge(Text[] o) {
                if (o!=null) {
                        for(int i=0; i<=5; i++){
                                if(mArray[i].getLength()==0){
                                        mArray[i].set(o[i].toString());
                                }
                        }
                }
                return true;
        }

        public Text[] terminate() {return mEmpty ? null : mArray;}
}
}