On Fri, Dec 10, 2010 at 8:09 PM, Vaibhav Kaushal <vaibhavkaushal...@gmail.com> 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.
I don't understand what it is you are proposing. Quicksort is usually swap based, and so the records would need to be the same size. Are you proposing to do an in-memory sort of pointers, which reference on-disk records? Or an on-disk sort of pointers which reference on-disk (but somewhere else) records? If you are swapping pointers on disk, you have to consider the write performance, not just the read performance. > I would like to do that (coding), but I do not have a SSD on my > machine! That doesn't mean you can't do the coding, it just means you can't test the performance. The barrier to get someone else to performance test it for you is a lot lower than the barrier to get someone else to write it for you and then performance test it for you. (But I can't test-drive it, as I don't have any computer which has both an SSD and a hard drive, just one or the other. And the one with SSD would be hard to compile PG on.) > :( Would it be impractical to try it for me? Again I do not > know how to test PG :( Yeah, I think it would be impractical. If I thought it would likely work, it would be different (at least, it might be if I had the right hardware). But I think it would likely not work. Cheers, Jeff -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
