starocean999 opened a new pull request, #67154:
URL: https://github.com/apache/doris/pull/67154
### What problem does this PR solve?
Issue Number: close #xxx
Related PR: #xxx
Problem Summary:
Nereids' default DECIMALV3 precision promotion
(`ComputeSignatureHelper.defaultDecimalV3PrecisionPromotion`) recursively
collects every
DECIMALV3 found in the argument types, computes a single global "wider"
type, and then
replaces ALL decimal slots with that one type via
`TypeCoercionUtils.replaceDecimalV3WithTarget`.
For `MAP<K, V>` where K and V are independent type variables with different
precision/scale, merging them into one wider type breaks correctness in two
ways
(they share the same type-derivation path):
1. `MAP_KEYS` (and other map consumers) silently turns legal keys into NULL.
Repro: a `MAP<DECIMAL(76,0), DECIMAL(76,18)>` built from a 76-digit
integral key
and `0.125000000000000000`. Widening the key slot to scale 18 overflows
the big
integral key, so `MAP_KEYS` returns `[null]` instead of the key.
2. `UNNEST(MAP)` (rewritten to `EXPLODE_MAP`) fails type analysis. The
promoted MAP
argument type no longer matches the original input MAP type.
Fix: promote each decimal slot independently instead of merging them. Each
slot
(MAP key/value, ARRAY item, scalar) keeps its own precision/scale derived
from its
own argument type; the wider type is only used for NULL-typed slots and the
placeholder return type. Vararg slots keep the previous behavior to avoid
changing
vararg decimal functions (e.g. `field`).
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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