spork-master/src/org/apache/pig/backend/hadoop/executionengine/spark/converter/FilterConverter.java
package org.apache.pig.backend.hadoop.executionengine.spark.converter;

import java.io.Serializable;
import java.util.List;

import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.POStatus;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.Result;
import org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POFilter;
import org.apache.pig.backend.hadoop.executionengine.spark.SparkUtil;
import org.apache.pig.data.Tuple;

import scala.runtime.AbstractFunction1;
import org.apache.spark.rdd.RDD;

/**
 * Converter that converts an RDD to a filtered RRD using POFilter
 */
@SuppressWarnings({ "serial" })
public class FilterConverter implements POConverter<Tuple, Tuple, POFilter> {

    @Override
    public RDD<Tuple> convert(List<RDD<Tuple>> predecessors,
            POFilter physicalOperator) {
        SparkUtil.assertPredecessorSize(predecessors, physicalOperator, 1);
        RDD<Tuple> rdd = predecessors.get(0);
        FilterFunction filterFunction = new FilterFunction(physicalOperator);
        return rdd.filter(filterFunction);
    }

    private static class FilterFunction extends
            AbstractFunction1<Tuple, Object> implements Serializable {

        private POFilter poFilter;

        private FilterFunction(POFilter poFilter) {
            this.poFilter = poFilter;
        }

        @Override
        public Boolean apply(Tuple v1) {
            Result result;
            try {
                poFilter.setInputs(null);
                poFilter.attachInput(v1);
                result = poFilter.getNextTuple();
            } catch (ExecException e) {
                throw new RuntimeException("Couldn't filter tuple", e);
            }

            if (result == null) {
                return false;
            }

            switch (result.returnStatus) {
            case POStatus.STATUS_OK:
                return true;
            case POStatus.STATUS_EOP: // TODO: probably also ok for EOS,
                                      // END_OF_BATCH
                return false;
            default:
                throw new RuntimeException(
                        "Unexpected response code from filter: " + result);
            }
        }
    }
}
