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 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
