[postgis-devel] Aggregate STYPE

[Sandro Santilli]

On Fri, Mar 02, 2018 at 02:52:03PM -0800, Paul Ramsey wrote:
> Memory test, ancient developers:
> 
> The CREATE AGGREGATE for ST_Union has
> 
>    stype = pgis_abs
> 
> The CREATE AGGREGATE for ST_AsMVT has
> 
>    stype = internal
> 
> Now, pgis_abs is just a stub type, it's not real at all, the
> input/output functions don't do anything, etc. So, is the retention of
> that type an echo of an earlier time when it wasn't possible to
> aggregate with an internal stype, or is there an *extra* reason why we
> don't just use stype=internal for ST_Union()?

My guess is we want "internal" nowadays, and "pgis_abs" is a leftover
from the far past. A quick look reveals that use of "internal" for
state types was introduced in PostGIS-2.4. PostgreSQL documentation
talk about an "internal" type even in version 7.3.

--strk;