fix typmod value in case of nvarchar(max), varchar(max), varbinary(max)

[skumawat2025]

Description

Previously, there was an issue in handling varchar(max) , nvarchar(max) and varbinary(max) in the code. Specifically, when dealing with atttypmod with a value of -8000 (representing TSQLMaxTypmod) in the PrepareRowDescription function for nvarchar and varchar, an incorrect value of atttypmod was being passed to the SetColMetadataForCharType function. This resulted in setting an incorrect maxSize for the column metadata entry.
Because of this if we assign a long string value to a nvarchar(max) variable with a length such that UTF16 output size is large it will throw a FATAL log elog(FATAL, "UTF16 output of varchar/bpchar exceeds max length");

Additionally, This PR limits a maximum scale value for (var)char, (var)binary, and (n)(var)char types. To do that, we set a limit of 8000 for (var)char and (var)binary, and a limit of 4000 for (n)(var)char.

Signed-off-by: Sandeep Kumawat [email protected]

Issues Resolved

BABEL-4547

Check List

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[KushaalShroff]

We dont need tests to test these changes??

[KushaalShroff]

Looks like this is a common issue for varbinarytypmodin, bpchartypmodin and varchartypmodin but you have fixed only n/varchar

[skumawat2025]

We dont need tests to test these changes??

Added test cases

[skumawat2025]

Looks like this is a common issue for varbinarytypmodin, bpchartypmodin and varchartypmodin but you have fixed only n/varchar

Yes, in tsql these three data-types support max as a scale. So these three have this issue.

1. varchar(max)
2. nvarchar(max)
3. varbinary(max)

In the latest commit I have made changes in parser for varchar(max), nvarchar(max).
For varbinary(max) we can not change typmod value to -1 before in parser because we are calling resolve_varbinary_typmod_from_exp (see code here) for some cases where typmod is -1 inside protocol. So I think we are left with option where we change atttypmod value in protocl for varbinary.