LuciferYang opened a new pull request, #64675:
URL: https://github.com/apache/doris/pull/64675
### What problem does this PR solve?
Problem Summary:
`NumericArithmetic.divideDecimal` (the DECIMALV2 constant-folding `divide`
function) guarded against division by zero by checking the **numerator**
(`first`) instead of the **denominator** (`second`):
```java
public static Expression divideDecimal(DecimalLiteral first, DecimalLiteral
second) {
if (first.getValue().compareTo(BigDecimal.ZERO) == 0) { // wrong
operand
return new NullLiteral(first.getDataType());
}
BigDecimal result = first.getValue().divide(second.getValue());
return new DecimalLiteral(result);
}
```
As a result, when both operands are DECIMALV2 literals:
- `0 / x` folded to **NULL** instead of `0` — a silent wrong result.
- `x / 0` skipped the guard and called `BigDecimal.divide(ZERO)`, throwing
`ArithmeticException`. This is caught by `ExpressionEvaluator.invoke` and the
expression is left unfolded (BE then evaluates it and returns NULL), so it is
not a crash, but the FE folding path is incorrect.
The sibling functions `divideDouble` and `divideDecimalV3` both correctly
check `second`. This PR aligns `divideDecimal` with them by checking the
denominator. Division by zero continues to return NULL, matching Doris/MySQL
semantics (Doris is MySQL-compatible here; it does not raise the ANSI `division
by zero` error).
### Release note
Fix incorrect constant folding of DECIMALV2 division: `0 / x` was folded to
NULL instead of 0.
### Check List (For Author)
- Test
- [x] Unit Test (added `testDivideDecimalZeroNumerator` and
`testDivideDecimalZeroDenominator` in `NumericArithmeticTest`)
- Behavior changed:
- [x] Yes. `0 / x` over constant DECIMALV2 values now correctly folds to
`0` instead of `NULL`. Division by zero still returns NULL (unchanged).
- Does this need documentation?
- [x] No.
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