On 12/11/2013 02:39 PM, Martijn van Oosterhout wrote: > In this discussion we've mostly used block = 1 postgresql block of 8k. > But when reading from a disk once you've read one block you can > basically read the following ones practically for free. > > So I wonder if you could make your sampling read always 16 consecutive > blocks, but then use 25-50% of the tuples. That way you get many more > tuples for the same amount of disk I/O seeks..
Yeah, that's what I meant by "tune this for the FS". We'll probably have to test a lot of different "block sizes" on different FSes before we arrive at a reasonable size, and even then I'll bet we have to offer a GUC. -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
