sqlite module returns empty instead of nill

[flaviut]

null is returned as "", not as nil as expected. A query with no results returns a row of ""s, not [] as expected.

related to #1364, I wouldn't be surprised if there were more places with this behavior.

[Araq]

This is the documented behaviour. Or at least it is well known. It's also the right behaviour because it's only ambiguous when it's a string and if your data model distinguishes between "" and NULL, it's broken. People who care about not losing information should use the dbj_ modules.

[flaviut]

Sorry, I disagree. Even though it is documented, it is not the expected behavior and leads to information loss, the avoidance of which is highly critical.

[Skrylar]

A string of length zero and a NUL are not identical semantically. (e.g. doing data analysis in R, there is a clear distinction between NA and an empty string; one could mean a user choose to enter a blank option, while the other means the information was not available in the dataset.)

[dom96]

I think the db module should distinguish between "" and NULL. The strutils module should then provide a isNullOrEmpty procedure similar to what C# provides.

[simonkrauter]

Any news after 2 years?
What about adding additional procs like getAllRowsNilable()?

[Araq]

We fixed the db modules since forever.

[dom96]

So the db modules now return nil?

[simonkrauter]

@Araq: What do you mean? I don't see the wanted behavior anywhere.
Code line https://github.com/nim-lang/Nim/blob/devel/lib/impure/db_sqlite.nim#L142 sets the empty string.