Re: [HACKERS] Block level parallel vacuum - Mailing list pgsql-hackers

On Mon, 11 Nov 2019 at 16:36, Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Mon, Nov 11, 2019 at 2:53 PM Mahendra Singh <mahi6run@gmail.com> wrote:
> >
> >
> > For small indexes also, we gained some performance by parallel vacuum.
> >
>
> Thanks for doing all these tests.  It is clear with this and previous
> tests that this patch has benefit in wide variety of cases.  However,
> we should try to see some worst cases as well.  For example, if there
> are multiple indexes on a table and only one of them is large whereas
> all others are very small say having a few 100 or 1000 rows.
>
I did some testing on the above suggested lines. Below is the summary:
Test case:(I created 16 indexes but only 1 index is large, other are very small)
create table test(a int, b int, c int, d int, e int, f int, g int, h int);
create index i3 on test (a) where a > 2000 and a < 3000;
create index i4 on test (a) where a > 3000 and a < 4000;
create index i5 on test (a) where a > 4000 and a < 5000;
create index i6 on test (a) where a > 5000 and a < 6000;
create index i7 on test (b) where a < 1000;
create index i8 on test (c) where a < 1000;
create index i9 on test (d) where a < 1000;
create index i10 on test (d) where a < 1000;
create index i11 on test (d) where a < 1000;
create index i12 on test (d) where a < 1000;
create index i13 on test (d) where a < 1000;
create index i14 on test (d) where a < 1000;
create index i15 on test (d) where a < 1000;
create index i16 on test (d) where a < 1000;
insert into test select i,i,i,i,i,i,i,i from generate_series(1,1000000) as i;
delete from test where a %2=0;
vacuum test;
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