Bruce Momjian wrote: > Vaibhav Kaushal wrote: > > On Fri, 2010-12-10 at 18:07 -0800, Josh Berkus wrote: > > > On 12/10/10 5:06 PM, Daniel Loureiro wrote: > > > > An quicksort method in > > > > sequential disk its just awful to be thinking in a non SSD world, but > > > > its possible in an SSD. > > > > > > So, code it. Shouldn't be hard to write a demo comparison. I don't > > > believe that SSDs make quicksort-on-disk feasible, but would be happy to > > > be proven wrong. > > > > I too do not believe it in normal case. However, considering the 'types' > > of SSDs, it may be feasible! Asking for 'the next page and getting it' > > has a time delay in the process. While on a regular HDD with spindles, > > the question is "where is that page located", with SSDs, the question > > disappears, because the access time is uniform in case of SSDs. Also, > > the access time is about 100 times fasterm which would change quite a > > few things about the whole process. > > What _is_ interesting is that Postgres often has sequential and > random/disk ways of doing things, and by reducing random_page_cost when > using SSDs, you automatically use more random operations, so in a way > the Postgres code was already prepared for SSD usage. Surprisingly, we > had to change very little.
To add to this very late reply, we basically had random methods to do things (in RAM), and sequential/random methods for disk. By changing random_page_cost, we favor doing random things on disk. The big question is whether there are random things we have never implemented on disk that now make sense --- off hand, I can't think of any. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
