Re: [COMMITTERS] pgsql: Don't generate parallel paths for rels with parallel-restricted

On Thu, Jun 9, 2016 at 11:38 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>
> > Could you answer my question about whether adjust_appendrel_attrs()
> > might translate Vars into non-Vars?
>
> Yes, absolutely.

Isn't this true only for UNION ALL cases and not for inheritance child
relations (at least that is what seems to be mentioned in comments
for translated_vars in AppendRelInfo)? If that is right, then I think
there shouldn't be a problem w.r.t parallel plans even if
adjust_appendrel_attrs() translate Vars into non-Vars, because for UNION
ALL it seems parent rels rtekind is RTE_SUBQUERY and we consider such rels
as parallel unsafe (see set_rel_consider_parallel()). So it doesn't matter
even if child rels target list contains any parallel unsafe expression, as
we are not going to create parallel paths for such relations.

With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com