org.apache.hadoop.hive.ql.udf.generic.GenericUDFLevenshtein.java Source code

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Here is the source code for org.apache.hadoop.hive.ql.udf.generic.GenericUDFLevenshtein.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */
package org.apache.hadoop.hive.ql.udf.generic;

import static org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorUtils.PrimitiveGrouping.STRING_GROUP;
import static org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorUtils.PrimitiveGrouping.VOID_GROUP;

import org.apache.commons.lang3.StringUtils;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorConverters.Converter;
import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector.PrimitiveCategory;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
import org.apache.hadoop.io.IntWritable;

/**
 * GenericUDFLevenshtein.
 *
 * This function calculates the Levenshtein distance between two strings.
 * Levenshtein distance is a string metric for measuring the difference between
 * two sequences. Informally, the Levenshtein distance between two words is the
 * minimum number of single-character edits (i.e. insertions, deletions or
 * substitutions) required to change one word into the other. It is named after
 * Vladimir Levenshtein, who considered this distance in 1965
 *
 */
@Description(name = "levenshtein", value = "_FUNC_(str1, str2) - This function calculates the Levenshtein distance between two strings.", extended = "Levenshtein distance is a string metric for measuring the difference between"
        + " two sequences. Informally, the Levenshtein distance between two words is the"
        + " minimum number of single-character edits (i.e. insertions, deletions or"
        + " substitutions) required to change one word into the other. It is named after"
        + " Vladimir Levenshtein, who considered this distance in 1965." + "Example:\n "
        + " > SELECT _FUNC_('kitten', 'sitting');\n 3")
public class GenericUDFLevenshtein extends GenericUDF {
    private transient Converter[] converters = new Converter[2];
    private transient PrimitiveCategory[] inputTypes = new PrimitiveCategory[2];
    private final IntWritable output = new IntWritable();

    @Override
    public ObjectInspector initialize(ObjectInspector[] arguments) throws UDFArgumentException {
        checkArgsSize(arguments, 2, 2);

        checkArgPrimitive(arguments, 0);
        checkArgPrimitive(arguments, 1);

        checkArgGroups(arguments, 0, inputTypes, STRING_GROUP, VOID_GROUP);
        checkArgGroups(arguments, 1, inputTypes, STRING_GROUP, VOID_GROUP);

        obtainStringConverter(arguments, 0, inputTypes, converters);
        obtainStringConverter(arguments, 1, inputTypes, converters);

        ObjectInspector outputOI = PrimitiveObjectInspectorFactory.writableIntObjectInspector;
        return outputOI;
    }

    @Override
    public Object evaluate(DeferredObject[] arguments) throws HiveException {
        String str0 = getStringValue(arguments, 0, converters);
        String str1 = getStringValue(arguments, 1, converters);

        if (str0 == null || str1 == null) {
            return null;
        }

        int dist = StringUtils.getLevenshteinDistance(str0, str1);
        output.set(dist);
        return output;
    }

    @Override
    public String getDisplayString(String[] children) {
        return getStandardDisplayString(getFuncName(), children);
    }

    @Override
    protected String getFuncName() {
        return "levenshtein";
    }
}