Jeff Janes wrote on 26.08.2012 20:45:
The seq scan is estimated to use sequential reads, while the index-only scan is estimated to use random reads (because the index is scanned in logical order, not physical order). If you set random_page_cost equal to seq_page_cost, that would artificially favor the index only scan. Also, your filler is highly compressible, which means the table is much smaller than you might think.
I tried it also with 750000 rows filled with 3 text columns of random string (between 20 and 15000 characters long). But also with that bigger data I just don't get an index scan. Seems that the prerequisites for an index only scan to happen are quite narrow. But given the fact that it's a brand new feature I guess it will improve over time ;) Regards Thomas -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
