/**
* 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;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.vector.VectorizedExpressions;
import org.apache.hadoop.hive.ql.exec.vector.expressions.gen.FuncLog2DoubleToDouble;
import org.apache.hadoop.hive.ql.exec.vector.expressions.gen.FuncLog2LongToDouble;
import org.apache.hadoop.hive.serde2.io.DoubleWritable;
/**
* UDFLog2.
*/
@Description(name = "log2",
value = "_FUNC_(x) - Returns the logarithm of x with base 2",
extended = "Example:\n"
+ " > SELECT _FUNC_(2) FROM src LIMIT 1;\n"
+ " 1")
@VectorizedExpressions({FuncLog2LongToDouble.class, FuncLog2DoubleToDouble.class})
public class UDFLog2 extends UDFMath {
private static final double LOG_2 = Math.log(2.0);
private final DoubleWritable result = new DoubleWritable();
/**
* Returns the logarithm of "a" with base 2.
*/
@Override
protected DoubleWritable doEvaluate(DoubleWritable a) {
if (a.get() <= 0.0) {
return null;
} else {
result.set(Math.log(a.get()) / LOG_2);
return result;
}
}
}