Got "LIMIT must not be negative" error as long as it is not a literal

[SteveLauC]

Describe the bug

$ datafusion-cli --color
DataFusion CLI v36.0.0
❯ select * from '1.parquet' limit 1 + 1;
Error during planning: LIMIT must not be negative
❯

It should work as long as it can be evaluated without schema or data, here is how duckdb handles it:

$ duckdb
v0.10.0 20b1486d11
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database.
D create table foo (id int);
D select * from foo limit 1 + 1;
┌────────┐
│   id   │
│ int32  │
├────────┤
│ 0 rows │
└────────┘

To Reproduce

See above, the table (parquet file) should not matter.

Expected behavior

1 + 1 should be evaluated to a constant 2.

Additional context

Related code:

https://github.com/apache/arrow-datafusion/blob/fc81bf10ea7cde55c6d58a670e15bfd0581ec8c2/datafusion/sql/src/query.rs#L240-L257

[SteveLauC]

So if DataFusion wants to follow DuckDB's behavior, then I guess we should evaluate that SQLExpr rather than simply converting it to DataFusion's Expr type.

[jonahgao]

I think ideally it should support any scalar expression. In PostgreSQL, even functions and scalar subqueries are allowed.

psql=> select * from t limit (select * from t limit 1);
 a
---
 1
(1 row)

psql=> select * from t limit random() + 1;
 a
---
 1
(1 row)

[SteveLauC]

any scalar expression

Yeah, as long as it can be evaluated to a number, it should work.

[alamb]

I think we could run the Expr simplifier / const folder on the limit value

I am not sure we can do so from within the planner itself 🤔

https://github.com/apache/arrow-datafusion/blob/1e4ddb6d86328cb6596bb50da9ccc654f19a83ea/datafusion/sql/src/query.rs#L249C1-L253C1