Pig UDF

pig.udf.COUNT.java

public class COUNT extends EvalFunc<Long> implements Algebraic{
    public Long exec(Tuple input) throws IOException {return count(input);}
    public String getInitial() {return Initial.class.getName();}
    public String getIntermed() {return Intermed.class.getName();}
    public String getFinal() {return Final.class.getName();}
    static public class Initial extends EvalFunc<Tuple> {
        public Tuple exec(Tuple input) throws IOException {return TupleFactory.getInstance().newTuple(count(input));}
    }
    static public class Intermed extends EvalFunc<Tuple> {
        public Tuple exec(Tuple input) throws IOException {return TupleFactory.getInstance().newTuple(sum(input));}
    }
    static public class Final extends EvalFunc<Long> {
        public Tuple exec(Tuple input) throws IOException {return sum(input);}
    }
    static protected Long count(Tuple input) throws ExecException {
        Object values = input.get(0);
        if (values instanceof DataBag) return ((DataBag)values).size();
        else if (values instanceof Map) return new Long(((Map)values).size());
    }
    static protected Long sum(Tuple input) throws ExecException, NumberFormatException {
        DataBag values = (DataBag)input.get(0);
        long sum = 0;
        for (Iterator (Tuple) it = values.iterator(); it.hasNext();) {
            Tuple t = it.next();
            sum += (Long)t.get(0);
        }
        return sum;
    }
}

pig.udf.IntMax.java

public class IntMax extends EvalFunc<Integer> implements Algebraic, Accumulator<Integer> {
    …….
    /* Accumulator interface */
    
    private Integer intermediateMax = null;
    
    @Override
    public void accumulate(Tuple b) throws IOException {
        try {
            Integer curMax = max(b);
            if (curMax == null) {
                return;
            }
            /* if bag is not null, initialize intermediateMax to negative infinity */
            if (intermediateMax == null) {
                intermediateMax = Integer.MIN_VALUE;
            }
            intermediateMax = java.lang.Math.max(intermediateMax, curMax);
        } catch (ExecException ee) {
            throw ee;
        } catch (Exception e) {
            int errCode = 2106;
            String msg = "Error while computing max in " + this.getClass().getSimpleName();
            throw new ExecException(msg, errCode, PigException.BUG, e);           
        }
    }

    @Override
    public void cleanup() {
        intermediateMax = null;
    }

    @Override
    public Integer getValue() {
        return intermediateMax;
    }
}

pig.udf.IsEmpty.java

import java.io.IOException;
import java.util.Map;

import org.apache.pig.FilterFunc;
import org.apache.pig.PigException;
import org.apache.pig.backend.executionengine.ExecException;
import org.apache.pig.data.DataBag;
import org.apache.pig.data.Tuple;
import org.apache.pig.data.DataType;

/**
 * Determine whether a bag or map is empty.
 */
public class IsEmpty extends FilterFunc {

    @Override
    public Boolean exec(Tuple input) throws IOException {
        try {
            Object values = input.get(0);
            if (values instanceof DataBag)
                return ((DataBag)values).size() == 0;
            else if (values instanceof Map)
                return ((Map)values).size() == 0;
            else {
                int errCode = 2102;
                String msg = "Cannot test a " +
                DataType.findTypeName(values) + " for emptiness.";
                throw new ExecException(msg, errCode, PigException.BUG);
            }
        } catch (ExecException ee) {
            throw ee;
        }
    }
}