Re: ARRAY() returning NULL instead of ARRAY[] resp. {}

Tom Lane wrote:
> I think he's got a good point, actually. We document the ARRAY-with-
> parens-around-a-SELECT syntax as
>
> The resulting one-dimensional array will have an element for
> each row in the subquery result, with an element type matching
> that of the subquery's output column.
>
> To me, that implies that a subquery result of no rows generates a
> one-dimensional array of no elements, not a null array.

OK, looks like I'm outnumbered.

But as far as I know, we have never had a way to produce a
one-dimensional empty array. Empty arrays thus far have been dimensionless.

Assuming we really want an empty 1D array, I created the attached patch.
This works fine, but now leaves a few oddities to be dealt with, e.g.:

regression=# select array_dims(array(select 1 where false));
array_dims
------------
[1:0]
(1 row)

Any thoughts on how this should be handled for an empty 1D array?

> The point Markus is complaining about seems like it should
> be easily fixable.

Well, "easily" is a relative term. My Postgres hacking neurons have
gotten kind of rusty lately -- but then maybe that was your underlying
point ;-)

Joe