Re: parallel vacuum comments

On Thu, Dec 16, 2021 at 1:56 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Wed, Dec 15, 2021 at 1:33 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >
> > I've attached an updated patch. The patch incorporated several changes
> > from the last version:
> >
> > * Rename parallel_vacuum_begin() to parallel_vacuum_init()
> > * Unify the terminology; use "index bulk-deletion" and "index cleanup"
> > instead of "index vacuum" and "index cleanup".
> >
>
> I am not sure it is a good idea to do this as part of the main patch
> as the intention of that is to just refactor parallel vacuum code. I
> suggest doing this as a separate patch.

Okay.

> Also, can we move the common
> code to be shared between vacuumparallel.c and vacuumlazy.c as a
> separate patch?

You mean vac_tid_reaped() and vac_cmp_itemptr() etc.? If so, do both
vacuumparallel.c and vacuumlazy.c have the same functions?

>
> Few other comments and questions:
> ============================
> 1. /* Outsource everything to parallel variant */
> - parallel_vacuum_process_all_indexes(vacrel, true);
> + LVSavedErrInfo saved_err_info;
> +
> + /*
> + * Outsource everything to parallel variant. Since parallel vacuum will
> + * set the error context on an error we temporarily disable setting our
> + * error context.
> + */
> + update_vacuum_error_info(vacrel, &saved_err_info,
> + VACUUM_ERRCB_PHASE_UNKNOWN,
> + InvalidBlockNumber, InvalidOffsetNumber);
> +
> + parallel_vacuum_bulkdel_all_indexes(vacrel->pvs, vacrel->old_live_tuples);
> +
> + /* Revert to the previous phase information for error traceback */
> + restore_vacuum_error_info(vacrel, &saved_err_info);
>
> Is this change because you want a separate error callback for parallel
> vacuum? If so, I suggest we can discuss this as a separate patch from
> the refactoring patch.

Because it seems natural to me that the leader and worker use the same
error callback.

Okay, I'll remove that change in the next version patch.

> 2. Is introducing bulkdel_one_index/cleanup_one_index related to new
> error context, or "Unify the terminology" task? Is there any other
> reason for the same?

Because otherwise both vacuumlazy.c and vacuumparallel.c will have the
same functions.

>
> 3. Why did you introduce
> parallel_vacuum_bulkdel_all_indexes()/parallel_vacuum_cleanup_all_indexes()?
> Is it because of your task "Unify the terminology"?

This is because parallel bulk-deletion and cleanup require different
numbers of inputs (num_table_tuples etc.) and the caller
(vacuumlazy.c) cannot set them directly to ParallelVacuumState.

>
> 4.
> @@ -3086,7 +2592,6 @@ lazy_cleanup_one_index(Relation indrel,
> IndexBulkDeleteResult *istat,
> ivinfo.report_progress = false;
> ivinfo.estimated_count = estimated_count;
> ivinfo.message_level = elevel;
> -
> ivinfo.num_heap_tuples = reltuples;
>
> This seems like an unrelated change.

Yes, but I think it's an unnecessary break so we can change it
together. Should it be done in a separate patch?

Regards,

--
Masahiko Sawada
EDB: https://www.enterprisedb.com/