Re: Сreate parallel aggregate

Grigory Smolkin <g(dot)smolkin(at)postgrespro(dot)ru> writes:
> I was trying to create a parallel aggregate with base_type parameter and
> failed

> postgres=# CREATE AGGREGATE ST_Extent_parallel (
> sfunc = ST_CombineBBox,
> combinefunc = ST_CombineBBox,
> finalfunc = box2d,
> stype = box3d,
> basetype = geometry,
> parallel = safe
> );
> ERROR: syntax error at or near "parallel"
> LINE 7: parallel = safe

Old-style CREATE AGGREGATE syntax is only meant to be used with the
options that existed at the time it was deprecated. It's unfortunate that
the error message is so obscure, but Bison doesn't give us a lot of wiggle
room to make it better, and frankly I don't especially care to put much
effort into that anyway. (The actual problem is that old_aggr_elem
has to use IDENT to avoid reduce/reduce conflicts, so none of the option
names can be keywords at all, not even unreserved ones.)

If we do anything about this at all, what I'd be inclined to do is shove
the old-style syntax into a footnote at the bottom of the reference page,
similarly to the way the legacy syntaxes for COPY are documented.
And probably we should strip out all but the historical options from
the list that we claim works with it.

A more aggressive answer would be to drop the old-style CREATE AGGREGATE
syntax altogether ... but seeing that we're still supporting pre-7.3 COPY
syntax, probably that won't fly.

regards, tom lane