At Sun, 30 Dec 2018 12:31:22 +0900, Kohei KaiGai <kaigai@heterodb.com> wrote in
<CAOP8fzY1Oqf-LGdrZT+TAu+JajwPGn1uYnpWWUPL=2LiattjYA@mail.gmail.com>
> 2018年12月30日(日) 4:12 Tom Lane <tgl@sss.pgh.pa.us>:
> On the other hands, the later hook must be dedicated to add regular paths,
> and also provides a chance for extensions to manipulate pre-built path-list
> including Gather-path.
> As long as I know, pg_hint_plan uses the set_rel_pathlist_hook to enforce
> a particular path-node, including Gather-node, by manipulation of the cost
> value. Horiguchi-san, is it right?
Mmm. I haven't expected that it is mentioned here.
Actually in the hook, it changes enable_* planner variables, or
directory manipuraltes path costs or even can clear and
regenerate the path list and gather paths for the parallel
case. It will be happy if we had a chance to manpurate partial
paths before genrating gahter paths.
regards.
--
Kyotaro Horiguchi
NTT Open Source Software Center