jacktengg opened a new pull request, #64531:
URL: https://github.com/apache/doris/pull/64531
Problem Summary: `FunctionIf` in BE is only reached through `nullif` because
SQL `if` is rewritten to `VectorizedIfExpr`. The `nullif` semantics can be
represented as `if(first = second, null, first)`, so this adds a Nereids
expression normalization rule to rewrite remaining `NullIf` expressions to `If`
after existing constant folding. The nullable-dependent conditional
simplification also falls back to the same rewrite so NullIf does not survive
that path.
Rewriting `nullif` to `if` must not be controlled by
`disable_nereids_expression_rules`, otherwise users could disable the rewrite
and still require BE `FunctionIf` support for `nullif`. This changes
`NullIfToIf` from a pattern rule with an `ExpressionRuleType` bit into a direct
visitor-based expression rewrite rule, and adds coverage that the rewrite still
runs when all expression rule bits are disabled.
### What problem does this PR solve?
Issue Number: close #xxx
Related PR: #xxx
Problem Summary:
### 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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