"Tom Lane" <[EMAIL PROTECTED]> writes: > Gregory Stark <[EMAIL PROTECTED]> writes: >> Recently there was a post on -performance about a particular case where >> Postgres doesn't make very good use of the I/O system. This is when you try >> to >> fetch many records spread throughout a table in random order. > >> http://archives.postgresql.org/pgsql-performance/2007-12/msg00005.php > > Since the OP in that thread has still supplied zero information > (no EXPLAIN, let alone ANALYZE, and no version info), it's pure > guesswork as to what his problem is.
Sure, consider it a hypothetical which needs further experimentation. That's part of why I ran (and will rerun) those synthetic benchmarks to test whether posix_fadvise() actually speeds up subsequent reads on a few operating systems. Surely any proposed patch will have to prove itself on empirical grounds too. I could swear this has been discussed in the past too. I seem to recall Luke disparaging Postgres on the same basis but proposing an immensely complicated solution. posix_fadvise or using libaio in a simplistic fashion as a kind of fadvise would be fairly lightweight way to get most of the benefit of the more complex solutions. -- Gregory Stark EnterpriseDB http://www.enterprisedb.com Get trained by Bruce Momjian - ask me about EnterpriseDB's PostgreSQL training! ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
