On Mon, 11 Nov 2019 at 16:36, Amit Kapila <amit.kapil...@gmail.com> wrote: > > On Mon, Nov 11, 2019 at 2:53 PM Mahendra Singh <mahi6...@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. >
Thanks Amit for your comments. 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; case 1: vacuum without using parallel workers. vacuum test; 228.259 ms case 2: vacuum with 1 parallel worker. vacuum (parallel 1) test; 251.725 ms case 3: vacuum with 3 parallel workers. vacuum (parallel 3) test; 259.986 >From above results, it seems that if indexes are small, then parallel vacuum is not beneficial as compared to normal vacuum. > Note: Please don't use the top-posting style to reply. Here, we use > inline reply. Okay. I will follow inline reply. Thanks and Regards Mahendra Thalor EnterpriseDB: http://www.enterprisedb.com
