deniskuzZ commented on code in PR #6878:
URL: https://github.com/apache/hive/pull/6878#discussion_r4294551129
##########
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/TruncDecimal.java:
##########
@@ -45,26 +45,9 @@ public TruncDecimal(int colNum, int scale, int
outputColumnNum) {
@Override
protected void trunc(ColumnVector inputColVector, ColumnVector
outputColVector, int i) {
- HiveDecimal input = ((DecimalColumnVector)
inputColVector).vector[i].getHiveDecimal();
-
- HiveDecimal output = trunc(input);
- ((DecimalColumnVector) outputColVector).vector[i] = new
HiveDecimalWritable(output);
- }
-
- protected HiveDecimal trunc(HiveDecimal input) {
- HiveDecimal pow = HiveDecimal.create(Math.pow(10, Math.abs(scale)));
-
- if (scale >= 0) {
- if (scale != 0) {
- long longValue = input.multiply(pow).longValue();
- return HiveDecimal.create(longValue).divide(pow);
- } else {
- return HiveDecimal.create(input.longValue());
- }
- } else {
- long longValue2 = input.divide(pow).longValue();
- return HiveDecimal.create(longValue2).multiply(pow);
- }
+ HiveDecimalWritable output = ((DecimalColumnVector)
outputColVector).vector[i];
Review Comment:
Fair points, thanks — agreed on keeping it allocation-free. To make the
in-place semantics explicit and keep callers to one line, could the decimal
overload take the output explicitly, like DecimalUtil.round(...) does?
````
public static void trunc(HiveDecimalWritable input, int scale,
HiveDecimalWritable output) {
output.set(input);
output.mutateSetScale(Math.max(scale, MIN_DECIMAL_SCALE),
DECIMAL_ROUND_DOWN);
}
````
Then `TruncDecimal` is `TruncUtils.trunc(inV.vector[i], scale,
outV.vector[i])` and `GenericUDFTrunc` is `TruncUtils.trunc(inputWritable,
scale, decimalOutput)`, and the input writable is never mutated.
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