/**
* 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.tajo.engine.function.math;
import org.apache.tajo.catalog.Column;
import org.apache.tajo.common.TajoDataTypes;
import org.apache.tajo.datum.Datum;
import org.apache.tajo.datum.DatumFactory;
import org.apache.tajo.datum.NullDatum;
import org.apache.tajo.engine.function.GeneralFunction;
import org.apache.tajo.engine.function.annotation.Description;
import org.apache.tajo.engine.function.annotation.ParamTypes;
import org.apache.tajo.storage.Tuple;
/**
* Function definition
*
* INT8 round(value FLOAT8)
*/
@Description(
functionName = "round",
description = "Round to nearest integer.",
example = "> SELECT round(42.4)\n"
+ "42",
returnType = TajoDataTypes.Type.INT8,
paramTypes = {@ParamTypes(paramTypes = {TajoDataTypes.Type.FLOAT4}),
@ParamTypes(paramTypes = {TajoDataTypes.Type.FLOAT8})}
)
public class Round extends GeneralFunction {
public Round() {
super(new Column[] {
new Column("x", TajoDataTypes.Type.FLOAT8)
});
}
@Override
public Datum eval(Tuple params) {
Datum valueDatum = params.get(0);
if(valueDatum instanceof NullDatum) {
return NullDatum.get();
}
double value = valueDatum.asFloat8();
// Note: there are various round up/down approaches (https://en.wikipedia.org/wiki/Rounding#Tie-breaking).
// Math.round uses an approach different from other programming languages, so the results of round function
// can be different from other DBMSs. For example, Math.round(-5.5) returns -5. In contrast,
// round function in MySQL and PostgreSQL returns -6. The below code is a workaround code for this.
if (value < 0) {
return DatumFactory.createInt8((long) Math.ceil(value - 0.5d));
} else {
return DatumFactory.createInt8((long) Math.floor(value + 0.5d));
}
}
}