ArrayRangeUDF.java

package brickhouse.udf.collect;
/**
 * Copyright 2012 Klout, Inc
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 **/


import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDF;
import org.apache.hadoop.hive.serde2.objectinspector.ListObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector.Category;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector.PrimitiveCategory;
import org.apache.hadoop.hive.serde2.objectinspector.StandardListObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.IntObjectInspector;


/**
 * Based on java.util.Arrays.copyOfRange
 */

public class ArrayRangeUDF extends GenericUDF {
    private ListObjectInspector listInspector;
    private StandardListObjectInspector returnInspector;
    private IntObjectInspector firstIntInspector, secondIntInspector;

    public int[] getIndexes(DeferredObject[] arg0) throws HiveException {
        int start, end, length;

        if (secondIntInspector == null) {
            start = 0;
            end = firstIntInspector.get(arg0[1].get());
            length = end;
        } else {
            start = firstIntInspector.get(arg0[1].get());
            end = secondIntInspector.get(arg0[2].get());
            length = end - start + 1;
        }

        return new int[]{start, end, length};
    }

    @Override
    public Object evaluate(DeferredObject[] arg0) throws HiveException {

        int indexes[] = getIndexes(arg0);

        int start = indexes[0];
        int end = indexes[1];
        int length = indexes[2];

        Object uninspListObj = arg0[0].get();

        int listSize = listInspector.getListLength(uninspListObj);

        Object truncatedListObj = returnInspector.create(length);

        for (int i = 0; i < end && i < listSize; ++i) {
            returnInspector.set(truncatedListObj, i, listInspector.getListElement(uninspListObj, i + start));
        }
        return truncatedListObj;
    }


    @Override
    public String getDisplayString(String[] arg0) {
        return "array_range(" + arg0[0] + ", " + arg0[1] + " , " + arg0[1] + " )";
    }


    @Override
    public ObjectInspector initialize(ObjectInspector[] arg0)
            throws UDFArgumentException {
        ObjectInspector first = arg0[0];
        if (first.getCategory() == Category.LIST) {
            listInspector = (ListObjectInspector) first;
        } else {
            throw new UDFArgumentException(" Expecting an array, one int and one optional int as arguments ");
        }

        ObjectInspector second = arg0[1];
        if (second.getCategory() == Category.PRIMITIVE) {
            PrimitiveObjectInspector secondPrim = (PrimitiveObjectInspector) second;
            if (secondPrim.getPrimitiveCategory() == PrimitiveCategory.INT) {
                firstIntInspector = (IntObjectInspector) second;
            } else {
                throw new UDFArgumentException(" Expecting an array, one int and one optional int as arguments ");
            }
        } else {
            throw new UDFArgumentException(" Expecting an array, one int and one optional int as arguments ");
        }

        if (arg0.length > 2) {

            ObjectInspector third = arg0[2];
            if (third != null) {
                if (third.getCategory() == Category.PRIMITIVE) {
                    PrimitiveObjectInspector thirdPrim = (PrimitiveObjectInspector) third;
                    if (thirdPrim.getPrimitiveCategory() == PrimitiveCategory.INT) {
                        secondIntInspector = (IntObjectInspector) third;
                    } else {
                        throw new UDFArgumentException(" Expecting an array, one int and one optional int as arguments ");
                    }
                } else {
                    throw new UDFArgumentException(" Expecting an array, one int and one optional int as arguments ");
                }
            }
        }


        returnInspector = ObjectInspectorFactory.getStandardListObjectInspector(
                listInspector.getListElementObjectInspector());
        return returnInspector;
    }

}