mrhhsg opened a new pull request, #68503:
URL: https://github.com/apache/doris/pull/68503
### What problem does this PR solve?
Issue Number: None
Related PR: #58200
Problem Summary:
`ntile(1 + 1) OVER (ORDER BY k)` was rejected at analysis time, although
the bucket is a constant expression that folds to `2`:
```
mysql> SELECT ntile(1 + 1) OVER (ORDER BY k) AS bucket
-> FROM (SELECT 1 AS k UNION ALL SELECT 2 UNION ALL SELECT 3) t;
ERROR 1105 (HY000): errCode = 2, detailMessage = The bucket parameter of
NTILE
must be a constant positive integer: ntile((1 + 1))
```
LAG/LEAD (#58200) and NTH_VALUE already accept such expressions, because
their literal checks run after constant folding.
Root cause: `Ntile.checkLegalityBeforeTypeCoercion` runs while the function
is being bound in the analyzer, before `FoldConstant` has turned `1 + 1`
into a literal, and it required the argument to already be a `Literal`.
Every non-literal constant expression therefore failed the check.
Fix: keep the integral-type, LARGEINT and constant checks as they are, then
fold the bucket with `FoldConstantRuleOnFE.evaluateWithoutContext` (the
pattern already used by `Stack`) and require the folded value to be an
integer literal greater than zero. Constant expressions such as `1 + 1`,
`cast(5 - 2 as bigint)` or `abs(-3)` are now accepted, while `0`, `1 - 1`,
`1 - 2`, a NULL result such as `cast('abc' as int)`, a non-constant column
and a LARGEINT bucket are still rejected with the existing error messages.
The backend registers `ntile` only for a non-nullable integer argument and
reads the bucket count from the argument column, so the bucket must still be
a literal when the plan is translated. A `checkLegalityAfterRewrite` is added
that requires a positive integer literal after rewrite (the same approach LAG
and LEAD use). When constant folding is skipped with
`debug_skip_fold_constant=true`, an unfolded expression such as
`cast('3' as int)` is now rejected with the NTILE message instead of failing
in the backend with `Agg Function ntile(int) is not implemented`.
After the fix the query above returns `1, 1, 2`.
### Release note
None
### Check List (For Author)
- Test:
- Unit Test: `NtileBucketTest` covers a literal bucket, foldable
constant expressions, expressions folded to zero/negative/NULL,
non-constant, non-integral and LARGEINT buckets, and the
after-rewrite check for literal and unfolded buckets.
- Regression test: `test_ntile_function` adds `ntile(1 + 1)`,
`ntile(cast(5 - 2 as bigint))`, `ntile(abs(-3))` with generated
output, error cases for `ntile(1 - 1)`, `ntile(1 - 2)` and
`ntile(cast('abc' as int))`, and cases with
`debug_skip_fold_constant=true`.
- Behavior changed: Yes (NTILE now accepts a constant bucket expression
that folds to a positive integer; such queries previously failed)
- Does this need documentation: No
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