feiniaofeiafei opened a new pull request, #69093:
URL: https://github.com/apache/doris/pull/69093
### What problem does this PR solve?
Issue Number: close #xxx
Related PR: #xxx
Problem Summary:
Eager aggregation restores join multiplicity by multiplying partial SUM
values by opposite-side counts. Ordinary decimal multiplication can reduce the
scale according to `decimal_overflow_scale`.
This causes either:
- An output type mismatch when an upper projection still expects the
original SUM type.
- Silent precision loss when the reduced-scale result reaches the query
output.
For example, a valid SUM of `0.0000000004` could become `0.000000`.
This Pr fix this problem:
- Introduce an internal decimal multiplication expression that preserves the
SUM result type.
- Cast the compensation input to the original SUM type when necessary.
- Preserve multiplication statistics estimation and prevent arithmetic
simplification or FE constant folding from reverting to ordinary decimal
multiplication semantics.
- Reuse the existing BE multiplication and overflow checks. No BE changes
are required.
### Release note
None
### Check List (For Author)
- Test <!-- At least one of them must be included. -->
- [ ] Regression test
- [ ] Unit Test
- [ ] Manual test (add detailed scripts or steps below)
- [ ] No need to test or manual test. Explain why:
- [ ] This is a refactor/code format and no logic has been changed.
- [ ] Previous test can cover this change.
- [ ] No code files have been changed.
- [ ] Other reason <!-- Add your reason? -->
- Behavior changed:
- [ ] No.
- [ ] Yes. <!-- Explain the behavior change -->
- Does this need documentation?
- [ ] No.
- [ ] Yes. <!-- Add document PR link here. eg:
https://github.com/apache/doris-website/pull/1214 -->
### Check List (For Reviewer who merge this PR)
- [ ] Confirm the release note
- [ ] Confirm test cases
- [ ] Confirm document
- [ ] Add branch pick label <!-- Add branch pick label that this PR should
merge into -->
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