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

Joe Conway wrote:
> 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 ;-)

No one responed to this email, so I will try.  Is this the one
dimmentional array you were talking about?
test=> select array_dims('{}'::integer[]); array_dims------------(1 row)

Why is [1:0] wrong to return?

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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