On Dec 13, 2007 10:06 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I guess that on purely philosophical grounds, it's not an unreasonable
> behavior. For example, "LIMIT n" means "output at most n tuples",
> not "output exactly n tuples". So when it outputs no tuples in the face
> of a negative limit, it's meeting its spec. If you want to throw an
> error for negative limit, shouldn't you logically also throw an error
> for limit larger than the actual number of rows produced by the subplan?
Hmm, good point. It does seem like if you're going to be pedantic,
you should be pedantic on both counts.
Though, I could understand throwing an error on a negative, because
that's likely a bug in the user's code and would enable them to find
out what's wrong. On the limit-larger-than-tuples-returned case, I
don't think it should throw an error because it's generally considered
as, "at most this many". I don't see a case where any user would
think that a negative limit *should* be allowed.
Don't we have any similar usability cases in the system like this,
where negatives are not allowed only for the sake of it being an
insane setting? I'm tired, but I thought we did.
--
Jonah H. Harris, Sr. Software Architect | phone: 732.331.1324
EnterpriseDB Corporation | fax: 732.331.1301
499 Thornall Street, 2nd Floor | jonah.harris@enterprisedb.com
Edison, NJ 08837 | http://www.enterprisedb.com/