Re: add PROCESS_MAIN to VACUUM - Mailing list pgsql-hackers

On Mon, Mar 06, 2023 at 01:13:37PM -0800, Nathan Bossart wrote:
> On Mon, Mar 06, 2023 at 03:48:28PM -0500, Melanie Plageman wrote:
> > On Mon, Mar 6, 2023 at 3:27 PM Nathan Bossart <nathandbossart@gmail.com> wrote:
> >> On Mon, Mar 06, 2023 at 02:40:09PM -0500, Melanie Plageman wrote:
> >> > I noticed in vacuum_rel() in vacuum.c where table_relation_vacuum() is
> >> > called, 4211fbd84 changes the else into an else if [1]. I understand
> >> > after reading the commit and re-reading the code why that is now, but I
> >> > was initially confused. I was thinking it might be nice to have a
> >> > comment mentioning why there is no else case here (i.e. that the main
> >> > table relation will be vacuumed on the else if branch).
> >>
> >> This was a hack to avoid another level of indentation for that whole block
> >> of code, but based on your comment, it might be better to just surround
> >> this entire section with an "if (params->options & VACOPT_PROCESS_MAIN)"
> >> check.  WDYT?
> > 
> > I think that would be clearer.
> 
> Here's a patch.  Thanks for reviewing.

> diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
> index 580f966499..fb1ef28fa9 100644
> --- a/src/backend/commands/vacuum.c
> +++ b/src/backend/commands/vacuum.c
> @@ -2060,23 +2060,25 @@ vacuum_rel(Oid relid, RangeVar *relation, VacuumParams *params, bool skip_privs)

I would move this comment inside of the outer if statement since it is
distinguishing between the two branches of the inner if statement.

Also, I would still consider putting a comment above that reminds us that
VACOPT_PROCESS_MAIN is the default and will vacuum the main relation.

>      /*
>       * Do the actual work --- either FULL or "lazy" vacuum
>       */
> -    if ((params->options & VACOPT_FULL) &&
> -        (params->options & VACOPT_PROCESS_MAIN))
> +    if (params->options & VACOPT_PROCESS_MAIN)
>      {
> -        ClusterParams cluster_params = {0};
> +        if (params->options & VACOPT_FULL)
> +        {
> +            ClusterParams cluster_params = {0};
>  
> -        /* close relation before vacuuming, but hold lock until commit */
> -        relation_close(rel, NoLock);
> -        rel = NULL;
> +            /* close relation before vacuuming, but hold lock until commit */
> +            relation_close(rel, NoLock);
> +            rel = NULL;
>  
> -        if ((params->options & VACOPT_VERBOSE) != 0)
> -            cluster_params.options |= CLUOPT_VERBOSE;
> +            if ((params->options & VACOPT_VERBOSE) != 0)
> +                cluster_params.options |= CLUOPT_VERBOSE;
>  
> -        /* VACUUM FULL is now a variant of CLUSTER; see cluster.c */
> -        cluster_rel(relid, InvalidOid, &cluster_params);
> +            /* VACUUM FULL is now a variant of CLUSTER; see cluster.c */
> +            cluster_rel(relid, InvalidOid, &cluster_params);
> +        }
> +        else
> +            table_relation_vacuum(rel, params, vac_strategy);
>      }
> -    else if (params->options & VACOPT_PROCESS_MAIN)
> -        table_relation_vacuum(rel, params, vac_strategy);
>  
>      /* Roll back any GUC changes executed by index functions */
>      AtEOXact_GUC(false, save_nestlevel);


- Melanie