Postgresql exceptions

[jcristovao]

Hello,

Perhaps I'm missing something obvious, but I somewhat was expecting withStmt' to return a SqlError, not a user error:

user error (Postgresql.withStmt': bad result status FatalError (("PGRES_FATAL_ERROR","ERROR: duplicate key value violates...

I guess this as to do with using fail which then gets turned into a UserError/IOError by with.

Would there be any way to bracket an insert just on SqlError, or do I have to bracket into the far more general IOError?

Thanks

[snoyberg]

I'm not able to work on the codebase right now (getting ready to travel), but this seems like a reasonable request. If someone sends a PR, I'll be happy to merge. Otherwise, I probably won't be able to get to this for another week or two.

[jcristovao]

So, I've took a stab at this, let me know what you think.
Thanks!

[snoyberg]

This looks good to me, sorry for the delayed review. Unless someone has an objection, I'd merge this in.

[jcristovao]

Thanks!

[AKurilin]

Would this by any chance expose the underlying Postgres error code or whatever it is translated to by the library being used to execute the query? e.g. PostgreSQL.Simple exposes a type for constraint violation errors. It's useful to pattern-match against for insertions and updates, when you want to perform the operation first, and handle the exception, as opposed to the less reliable check & insert approach.

[jcristovao]

That's precisely my use case, and why I submitted this patch ;)

[jonkri]

+1

[gregwebs]

@snoyberg do you know what the status of this issue is?

[snoyberg]

IIRC, I'm waiting for @jcristovao to send a PR with his change. Though if people are more eager to see this go out the door, anyone else could theoretically take @jcristovao's commit and send it as a PR him/herself.

[jcristovao]

Ok, I forgot I did not actually submited this as a PR, my bad.
Will take care of this tomorrow

[jonkri]

Thanks! :)