2016-12-21 0:01 GMT+01:00 Tom Lane <t...@sss.pgh.pa.us>: > Pavel Stehule <pavel.steh...@gmail.com> writes: > > I am trying to fix slow query on PostgreSQL 9.5.4. > > The data are almost in RAM > > If it's all in RAM, you'd likely be well-served to lower random_page_cost. > It looks to me like the planner is estimating pretty accurately how many > heap fetches will be eliminated by using the extra index; where it's off > seems to be in the cost of those heap fetches relative to the index work. >
When I decrease random page cost, then the cost of bitmapscan was decreased too https://explain.depesz.com/s/7CAJ .. random page cost 2 https://explain.depesz.com/s/iEBW .. random page cost 2, bitmapscan off https://explain.depesz.com/s/W4zw .. random page cost 2 https://explain.depesz.com/s/Gar .. random page cost 1, bitmapscan off I played with other costs, but without any success, the cost of bitmapscan is significantly cheaper then index scan. Regards Pavel > regards, tom lane >
