viirya opened a new pull request, #24380:
URL: https://github.com/apache/datafusion/pull/24380
## Which issue does this PR close?
- Closes #24379.
## Rationale for this change
`simplify_regex_expr` rewrites `col ~ '.*'` to `col IS NOT NULL`. For a NULL
input that returns `false`, but `NULL ~ '.*'` is `NULL` under three-valued
logic — so the rewrite produces wrong results in a projection context:
```sql
SELECT s, s ~ '.*' FROM (VALUES (CAST(NULL AS VARCHAR)), ('x')) t(s);
-- NULL row currently returns `false`; it should be NULL
```
The `!~` (`RegexNotMatch`) branch of the same rule is already NULL-aware
(`col IS NULL AND NULL`); only the `~` branch dropped the NULL.
## What changes are included in this PR?
- Rewrite `col ~ '.*'` to `col IS NOT NULL OR NULL` — `true` for a non-NULL
string, `NULL` for a NULL input.
- In a WHERE filter both FALSE and NULL reject the row, so filter *results*
are unchanged; only the plan text and projection-context values differ.
Existing filter-plan expectations in `simplify_expr.slt` and the
`test_simplify_regex_special_cases` unit test are updated accordingly, and a
projection regression test is added.
## Are these changes tested?
Yes.
- New projection regression test in `simplify_expr.slt` asserting `col ~
'.*'` returns `true`/`true`/`NULL` for `'foo'`/`''`/`NULL`.
- Updated the two filter-context plan expectations (logical + physical) that
previously encoded the `IS NOT NULL` rewrite.
- `simplify_expr.slt`, the `regexp/*` SLTs, and the optimizer simplify unit
tests all pass.
## Are there any user-facing changes?
`col ~ '.*'` in a projection now returns `NULL` for a NULL input instead of
`false`, matching SQL semantics. No API changes.
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