Re: BUG #4509: array_cat's null behaviour is inconsistent

Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> Kevin Field wrote:
>> select array_cat(null::integer[], '{3}'::integer[]);
>> ...doesn't return NULL, which it should, for consistency.

> Doesn't make sense to me either. I found that this was changed between
> 8.1 (where it returns null) and 8.2, but I find nothing in the
> respective release notes or commit messages about this change. Tom?

Hm, I seem to have changed it in the patch that added support for nulls
within arrays, but I don't recall the reasoning for this detail ATM.

I'm loath to change just this one thing though. If we're going to
monkey with it, I think we should start by having a thought-through
proposal about the behavior of all the array functions for corner
cases like null arrays and empty arrays (cf recent discussion about
zero-dimensional arrays).

regards, tom lane