org.apache.hadoop.hive.ql.udf.UDFLog 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;
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.FuncLogWithBaseDoubleToDouble;
import org.apache.hadoop.hive.ql.exec.vector.expressions.FuncLogWithBaseLongToDouble;
import org.apache.hadoop.hive.ql.exec.vector.expressions.gen.FuncLnDoubleToDouble;
import org.apache.hadoop.hive.ql.exec.vector.expressions.gen.FuncLnLongToDouble;
import org.apache.hadoop.hive.serde2.io.DoubleWritable;
import org.apache.hadoop.hive.serde2.io.HiveDecimalWritable;
/**
* UDFLog.
*/
@Description(name = "log",
value = "_FUNC_([b], x) - Returns the logarithm of x with base b",
extended = "Example:\n"
+ " > SELECT _FUNC_(13, 13) FROM src LIMIT 1;\n"
+ " 1")
@VectorizedExpressions({FuncLogWithBaseLongToDouble.class, FuncLogWithBaseDoubleToDouble.class,
FuncLnLongToDouble.class, FuncLnDoubleToDouble.class})
public class UDFLog extends UDFMath {
private final DoubleWritable result = new DoubleWritable();
/**
* Returns the logarithm of "a" with base "base".
*/
public DoubleWritable evaluate(DoubleWritable base, DoubleWritable a) {
if (a == null || base == null) {
return null;
}
return log(base.get(), a.get());
}
/**
* Get the logarithm of the given decimal input with the given decimal base.
*/
public DoubleWritable evaluate(HiveDecimalWritable baseWritable, HiveDecimalWritable writable) {
if (baseWritable == null || writable == null) {
return null;
}
double base = baseWritable.doubleValue();
double d = writable.doubleValue();
return log(base, d);
}
/**
* Returns the natural logarithm of "a".
*/
@Override
protected DoubleWritable doEvaluate(DoubleWritable a) {
if (a.get() <= 0.0) {
return null;
} else {
result.set(Math.log(a.get()));
return result;
}
}
private DoubleWritable log(double base, double input) {
if (base <= 1.0 || input <= 0.0) {
return null;
}
result.set(Math.log(input) / Math.log(base));
return result;
}
}