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  * "License"); you may not use this file except in compliance
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 * See the License for the specific language governing permissions and
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package org.apache.pig.backend.hadoop.executionengine.mapReduceLayer;
A special implementation of combiner used only for distinct. This combiner does not even parse out the records. It just throws away duplicate values in the key in order ot minimize the data being sent to the reduce.
public class DistinctCombiner {
    public static class Combine 
        private final Log log = LogFactory.getLog(getClass());
        ProgressableReporter pigReporter;
Configures the reporter
        protected void setup(Context contextthrows IOExceptionInterruptedException {
             = new ProgressableReporter();
The reduce function which removes values.
        protected void reduce(PigNullableWritable keyIterable<NullableTupletupIterContext context
                throws IOExceptionInterruptedException {
            // Take the first value and the key and collect
            // just that.
            Iterator<NullableTupleiter = tupIter.iterator();
            NullableTuple val =;
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