Greg Smith <[EMAIL PROTECTED]> writes: >> I have an updated patch I'll be sending along shortly. You might want to test >> with that? > > Obviously I've got everything setup to test right now, am currently analyzing > your earlier patch and the sequential scan fork that derived from it. If > you've got a later version of the bitmap heap scan one as well, I'll replace > the one I had been planning to test (your bitmap-preread-v9) with that one > when > it's available.
Well here you go. It includes: . Bitmap heap scans (as before) . Index scans . Setting POSIX_FADV_SEQUENTIAL for bulk sequential scans . Improved (ie, debugged) autoconf tests for posix_fadvise (and posix_fallocate though I don't have any code using it yet) The bitmap heap scans are still prefetching the number of buffers I estimate based on effective_spindle_count according to my magic formula. We've been discussing throwing that out, I just haven't modified this to do that yet. Index scans prefetch all pages for matching index tuples on the leaf page when we do page-at-a-time scans. I haven't bothered doing the gradual ramp-up or keeping a ring of the optimal size prefetched. The sequential scan stuff is based on Zoltan's posts but done in a different way. It passes an i/o access strategy to smgr and fd.c which keeps track of what the previous strategy was and calls posix_fadvise if it's changed. This will correctly handle queries which reference the same table twice even if one reference is a sequential scan and the other is an index lookup. I have *not* been able to observe any significant effect from POSIX_FADV_SEQUENTIAL but I'm not sure what circumstances it was a problem. It sounds like it's a peculiar situation which is not easy to reliably reproduce.
bitmap-preread-v18.diff.gz
Description: Binary data
-- Gregory Stark EnterpriseDB http://www.enterprisedb.com Ask me about EnterpriseDB's Slony Replication support!
-- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
