org.apache.hadoop.hive.ql.udf.generic.GenericUDFLevenshtein Maven / Gradle / Ivy
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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";
}
}