Re: [HACKERS] Block level parallel vacuum

On Thu, Oct 10, 2019 at 2:19 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Fri, Oct 4, 2019 at 4:18 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > On Wed, Oct 2, 2019 at 7:29 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >>
>
> Few more comments:

Thank you for reviewing the patch!

> ---------------------------------
> 1. Caurrently parallel vacuum is allowed for temporary relations
> which is wrong. It leads to below error:
>
> postgres=# create temporary table tmp_t1(c1 int, c2 char(10));
> CREATE TABLE
> postgres=# create index idx_tmp_t1 on tmp_t1(c1);
> CREATE INDEX
> postgres=# create index idx1_tmp_t1 on tmp_t1(c2);
> CREATE INDEX
> postgres=# insert into tmp_t1 values(generate_series(1,10000),'aaaa');
> INSERT 0 10000
> postgres=# delete from tmp_t1 where c1 > 5000;
> DELETE 5000
> postgres=# vacuum (parallel 2) tmp_t1;
> ERROR: cannot access temporary tables during a parallel operation
> CONTEXT: parallel worker
>
> The parallel vacuum shouldn't be allowed for temporary relations.

Fixed.

>
> 2.
> --- a/doc/src/sgml/ref/vacuum.sgml
> +++ b/doc/src/sgml/ref/vacuum.sgml
> @@ -34,6 +34,7 @@ VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [
> <replaceable class="paramet
> SKIP_LOCKED [ <replaceable class="parameter">boolean</replaceable> ]
> INDEX_CLEANUP [ <replaceable
> class="parameter">boolean</replaceable> ]
> TRUNCATE [ <replaceable class="parameter">boolean</replaceable> ]
> + PARALLEL [ <replaceable
> class="parameter">integer</replaceable> ]
>
> Now, if the user gives a command like Vacuum (analyze, parallel)
> <table_name>; it is not very obvious that a parallel option will be
> only used for vacuum purposes but not for analyze. I think we can add
> a note in the docs to mention this explicitly. This can avoid any
> confusion.

Agreed.

Attached the latest version patch although the memory usage problem is
under discussion. I'll update the patches according to the result of
that discussion.

Regards,

--
Masahiko Sawada