Re: [HACKERS] Block level parallel vacuum

On Wed, Oct 2, 2019 at 7:29 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
I have started reviewing this patch and I have some cosmetic comments.
I will continue the review tomorrow.

+This change adds PARALLEL option to VACUUM command that enable us to
+perform index vacuuming and index cleanup with background
+workers. Indivisual

/s/Indivisual/Individual/

+ * parallel worker processes. Individual indexes is processed by one vacuum
+ * process. At beginning of lazy vacuum (at lazy_scan_heap) we prepare the

/s/Individual indexes is processed/Individual indexes are processed/
/s/At beginning/ At the beginning

+ * parallel workers. In parallel lazy vacuum, we enter parallel mode and
+ * create the parallel context and the DSM segment before starting heap
+ * scan.

Can we extend the comment to explain why we do that before starting
the heap scan?

+ else
+ {
+ if (for_cleanup)
+ {
+ if (lps->nworkers_requested > 0)
+ appendStringInfo(&buf,
+ ngettext("launched %d parallel vacuum worker for index cleanup
(planned: %d, requested %d)",
+ "launched %d parallel vacuum workers for index cleanup (planned:
%d, requsted %d)",
+ lps->pcxt->nworkers_launched),
+ lps->pcxt->nworkers_launched,
+ lps->pcxt->nworkers,
+ lps->nworkers_requested);
+ else
+ appendStringInfo(&buf,
+ ngettext("launched %d parallel vacuum worker for index cleanup (planned: %d)",
+ "launched %d parallel vacuum workers for index cleanup (planned: %d)",
+ lps->pcxt->nworkers_launched),
+ lps->pcxt->nworkers_launched,
+ lps->pcxt->nworkers);
+ }
+ else
+ {
+ if (lps->nworkers_requested > 0)
+ appendStringInfo(&buf,
+ ngettext("launched %d parallel vacuum worker for index vacuuming
(planned: %d, requested %d)",
+ "launched %d parallel vacuum workers for index vacuuming (planned:
%d, requested %d)",
+ lps->pcxt->nworkers_launched),
+ lps->pcxt->nworkers_launched,
+ lps->pcxt->nworkers,
+ lps->nworkers_requested);
+ else
+ appendStringInfo(&buf,
+ ngettext("launched %d parallel vacuum worker for index vacuuming
(planned: %d)",
+ "launched %d parallel vacuum workers for index vacuuming (planned: %d)",
+ lps->pcxt->nworkers_launched),
+ lps->pcxt->nworkers_launched,
+ lps->pcxt->nworkers);
+ }

Multiple places I see a lot of duplicate code for for_cleanup is true
or false. The only difference is in the error message whether we give
index cleanup or index vacuuming otherwise complete code is the same
for
both the cases. Can't we create some string and based on the value of
the for_cleanup and append it in the error message that way we can
avoid duplicating this at many places?

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com