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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.drill.common.util;
/*
* Here we compute the scale and precision of the output decimal data type
* based on the input scale and precision. Since division operation can be
* a multiplication operation we compute the scale to be the sum of the inputs.
* Eg: Input1 : precision = 5, scale = 3 ==> max integer digits = 2
* Input2 : precision = 7, scale = 4 ==> max integer digits = 3
*
* Output: max integer digits ==> 2 (left integer digits) + 4 (right scale, when divide results in multiplication)
* max scale ==> 3 + 4 = 7
*
* Minimum precision required ==> 6 + 7 = 13
*
* Since our minimum precision required is 13, we will use DECIMAL18 as the output type
* but since this is divide we will grant the remaining digits in DECIMAL18 to scale
* so we have the following
* output scale ==> 7 + (18 - 13) = 12
* output precision ==> 18
*/
public class DecimalScalePrecisionDivideFunction extends DrillBaseComputeScalePrecision {
public DecimalScalePrecisionDivideFunction(int leftPrecision, int leftScale, int rightPrecision, int rightScale) {
super(leftPrecision, leftScale, rightPrecision, rightScale);
}
@Override
public void computeScalePrecision(int leftPrecision, int leftScale, int rightPrecision, int rightScale) {
// compute the output scale and precision here
outputScale = leftScale + rightScale;
int leftIntegerDigits = leftPrecision - leftScale;
int maxResultIntegerDigits = leftIntegerDigits + rightScale;
outputPrecision = CoreDecimalUtility.getPrecisionRange(outputScale + maxResultIntegerDigits);
// Output precision should be greater or equal to the input precision
outputPrecision = Math.max(outputPrecision, Math.max(leftPrecision, rightPrecision));
// Try and increase the scale if we have any room
outputScale = (outputPrecision - maxResultIntegerDigits >= 0) ? (outputPrecision - maxResultIntegerDigits) : 0;
}
}
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