Lordworms commented on PR #10746:
URL: https://github.com/apache/datafusion/pull/10746#issuecomment-2143625294
> I guess I should have added more examples in #10743. So I would argue that
it would be better if the following expressions produced equivalent results:
>
> 1. SELECT '12345'::VARCHAR(2)
> 2. SELECT s::VARCHAR(2) FROM (VALUES ('12345')) t(s)
> 3. SELECT s::VARCHAR(2) FROM vals
>
> But this PR only addresses the first case.
Currently, I think it is tricky to do 2 and 3 since Datafusion would
transform the ast::DataType into arrow::DataType in function
sql_expr_to_logical_expr_internal, however, instead of directing knowing the
string in 1, 2, and 3 would generate a different AST tree like
<img width="976" alt="image"
src="https://github.com/apache/datafusion/assets/48054792/a25e00a5-c295-4e4d-9d71-2fce96e443ce";>
if we want to do the validation on 2 and 3, we need to keep the information
of ast::DataType::Varchar(Some(IntegerLength { length, .. })), but I don't know
whether it is a need currently.
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