2011/10/9 Pavel Stehule <pavel.stehule@xxxxxxxxx>: > 2011/10/9 Tom Lane <tgl@xxxxxxxxxxxxx>: >> Pavel Stehule <pavel.stehule@xxxxxxxxx> writes: >>> 2011/10/9 Thom Brown <thom@xxxxxxxxx>: >>>> On 9 October 2011 04:35, Pavel Stehule <pavel.stehule@xxxxxxxxx> wrote: >>>>> It has a sense - index only scan it is faster (and significantly >>>>> faster) on wider tables - or tables with strings where TOAST is not >>>>> active. Maybe there is a some issue because on thin tables is slower >>>>> (and I expect a should be faster everywhere). >> >>>> No, that's my point, I re-tested it on a table with just 2 int >>>> columns, and the results are roughly the same. I added all the >>>> columns to make it expensive to fetch the column being queried. >> >>> then I don't understand >> >> Are you sure you've remembered to vacuum the test table? I get results >> like yours (ie, no speed benefit for index-only scan) if the table >> doesn't have its visibility-map bits set. > > it should be - I didn't do VACUUM > yes, After VACUUM I got a significantly better times - index only scan is about 5-6x better Regards Pavel Stehule > > Regards > > Pavel >> >> regards, tom lane >> > -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
