On Mon, Jan 11, 2010 at 3:52 AM, Robert Haas <robertmh...@gmail.com> wrote:
> On Sun, Jan 10, 2010 at 10:53 AM, Kevin Grittner > <kevin.gritt...@wicourts.gov> wrote: > > seq_page_cost = 0.1 > > random_page_cost = 0.1 > > These might not even be low enough. The reason why bitmap index scans > win over plain index scans, in general, is because you make one pass > through the heap to get all the rows you need instead of bouncing > around doing lots of random access. But of course if all the data is > in RAM then this argument falls down. > > If these aren't enough to get the query planner to DTRT, then the OP > might want to try lowering them further and seeing how low he has to > go to flip the plan... > So if this query usually does *not* hit the cache, it will be probably faster if I leave it like that? While testing a query I execute it that much that it's always getting into the cache. However, since other applications run on the same server, I think that infrequently used data gets flushed after a while, even if the DB could fit in the RAM. -- Mathieu
