skeleton for GenericUDAF

SkeletonUDAF.java

package somewhere;

import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDFArgumentLengthException;
import org.apache.hadoop.hive.ql.exec.UDFArgumentTypeException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.parse.SemanticException;
import org.apache.hadoop.hive.ql.udf.generic.AbstractGenericUDAFResolver;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDAFEvaluator;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDAFParameterInfo;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;

@Description(name = "skeleton",
        value = "_FUNC_(something) - Returns something")
public class SkeletonUDAF extends AbstractGenericUDAFResolver {
    @Override
    public GenericUDAFEvaluator getEvaluator(GenericUDAFParameterInfo info) throws SemanticException {
        final ObjectInspector[] OIs = info.getParameterObjectInspectors();
        
        if (OIs.length != 0) {
            throw new UDFArgumentLengthException("Specify  arguments.");
        }
        
        if (/*check type of OIs*/) {
            throw new UDFArgumentTypeException(0, "Only  type argument is acceptable but "
                    + OIs[0].getTypeName() + " was passed as ``");
        }
        
        return new SkeletonUDAFEvaluator();
    }

    private static class SkeletonUDAFEvaluator extends GenericUDAFEvaluator {
        // declare local OIs for PARTIAL1 and COMPLETE: OIs for a original data
        
        // declare local OIs for PARTIAL2 and FINAL: OIs for partial aggregations
        // private StructObjectInspector structOI;
        // private StructField skeletonField;
        // private ObjectInspector skeletonOI;

        @AggregationType(estimable = true)
        static class SkeletonAggregationBuffer extends AbstractAggregationBuffer {
            // declare variables for buffering
            
            @Override
            public int estimate() {
                return 0; // estimating value for size of *this* buffer
            }
            
            public void reset() {
                // enable this buffer to be reused
            }
        }

        @Override
        public ObjectInspector init(Mode mode, ObjectInspector[] OIs) throws HiveException {
            super.init(mode, OIs);
            
            if (mode == Mode.PARTIAL1 || mode == Mode.COMPLETE) {
                // init local OIs by an original data
            } else {
                // init local OIs by a partial aggregation
                // structOI = (StructObjectInspector) OIs[0];
                // skeletonField = structOI.getStructFieldRef("skeleton");
                // skeletonOI = (ObjectInspector) skeletonField.getFieldObjectInspector();
            }
            
            if (mode == Mode.PARTIAL1 || mode == Mode.PARTIAL2) {
                // List<ObjectInspector> fieldOIs = new ArrayList<ObjectInspector>();
                // fieldOIs.add(ObjectInspectorFactory...);
                // return ObjectInspectorFactory.getStandardStructObjectInspector(
                //        Arrays.asList("skeleton"), fieldOIs);
                    
                return null; // OI of a partial aggregation generated by `#terminatePartial(...)`
            } else {
                return null; // OI of a final result value, which is scalar, generated by `#terminate(...)`
            }
        }

        @Override
        public AbstractAggregationBuffer getNewAggregationBuffer() throws HiveException {
            final SkeletonAggregationBuffer myAgg = new SkeletonAggregationBuffer();
            reset(myAgg);
            return myAgg;
        }

        @Override
        public void reset(AggregationBuffer agg) throws HiveException {
            final SkeletonAggregationBuffer myAgg = (SkeletonAggregationBuffer) agg;
            myAgg.reset();
        }

        @Override
        public void iterate(AggregationBuffer agg, Object[] parameters) throws HiveException {
            final SkeletonAggregationBuffer myAgg = (SkeletonAggregationBuffer) agg;
            
            // update myAgg by parameters
        }

        @Override
        public void merge(AggregationBuffer agg, Object other) throws HiveException {
            if (other == null) {
                return;
            }
            
            final SkeletonAggregationBuffer myAgg = (SkeletonAggregationBuffer) agg;
            
            // Object skeleton = skeletonOI.get(structOI.getStructFieldData(other, skeletonField));
            
            // merge other into myAgg
        }

        @Override
        public Object terminatePartial(AggregationBuffer agg) throws HiveException {
            final SkeletonAggregationBuffer myAgg = (SkeletonAggregationBuffer) agg;
            
            // Object[] partialResult = new Object[1];
            // partialResult[0] = witableSkeleton;
            // return partialResult;
            
            // return writable partial result by myAgg
            
            return null;
        }

        @Override
        public Object terminate(AggregationBuffer agg) throws HiveException {
            final SkeletonAggregationBuffer myAgg = (SkeletonAggregationBuffer) agg;
            
            // return writable result by myAgg
            
            return null;
        }
    }
}