Re: [PATCH] Exorcise "zero-dimensional" arrays (Was: Re: Should array_length() Return NULL)

On 4 April 2013 01:10, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I think though that the upthread argument that we'd have multiple
> interpretations of the same thing is bogus. To me, the core idea that's
> being suggested here is that '{}' should mean a zero-length 1-D array,
> not a zero-D array as formerly. We would still need a way to represent
> zero-D arrays, if only because they'd still exist on-disk in existing
> databases (assuming we're not willing to break pg_upgrade for this).

Tom,

My thought was that on-disk zero-D arrays should be converted into
empty 1-D arrays (with default lower bounds of course) when they are
read by array_recv. Any SQL operation on your zero-D arrays would
therefore resolve as though they were 1-D. A pg_dump/restore would
result in the arrays being 1-D on the restore side. If pg_upgrade
conserves the zero-D array in binary form, that's okay since the
receiving end will just treat it as 1-D out of array_recv anyway.

My intention was that the zero-D array could continue to live
indefinitely in binary form, but would never be observable as such by
any application code.

Cheers,
BJ