feat: support expression in limit clause #19834

0 / 1 tasks completed (+7 optional)

1 task still to be completed (+7 optional)

Task	Status
I have written necessary rustdoc comments.	Incomplete
This validation logic is better placed in binder, and `BoundQuery::limit` remains an `Option<u64>`. Planner is in charge of transforming SQL into a plan graph.	Incomplete
We can do cast first and then `try_fold_const`, rather than using `is_const` and `fold_const` separately.	Incomplete
The allowed casts in PostgreSQL is `assign` rather than `explicit`. (`int` requires `implicit`, `decimal` requires `assign`, `jsonb` requires `explicit`. I tested in PostgreSQL and `LIMIT '1'::jsonb` is not allowed.)	Incomplete
When the evaluated output is `None`, which means SQL NULL, PostgreSQL treats it as no limit. Let's add a test case for this.	Incomplete
Test error cases: wrong type, not const, eval error, negative	Incomplete
Wrong type already handled as `cast_assign` error above.	Incomplete
Not const corresponds to `None`. The test case can be `select 1 limit generate_series(1, 2);`	Incomplete
Eval error corresponds to `Some(Err(_))`. The test case can be `select 1 limit 2/0;`	Incomplete

Task	Status
I have added necessary unit tests and integration tests.	Incomplete
I have added test labels as necessary.	Incomplete
I have added fuzzing tests or opened an issue to track them.	Incomplete
My PR contains breaking changes.	Incomplete
My PR changes performance-critical code, so I will run (micro) benchmarks and present the results.	Incomplete
My PR contains critical fixes that are necessary to be merged into the latest release.	Incomplete
My PR needs documentation updates.	Incomplete