Hello, I wonder if POSIX_FADV_RANDOM and POSIX_FADV_SEQUENTIAL are still innacurate for postgreSQL ?
I find «A related problem is that the smgr uses the same FD to access the same relation no matter how many scans are in progress. Think about a complex query that is doing both a seqscan and an indexscan on the same relation (a self- join could easily do this). You'd really need to change this if you want POSIX_FADV_SEQUENTIAL and POSIX_FADV_RANDOM to get set usefully. » (tom lane, 2003) And also : « Surely POSIX_FADV_SEQUENTIAL is the one intended to hint seq scans, and POSIX_FADV_RANDOM to hint random access. No? ISTM, _WILLNEED seems just right for small random-access blocks. Anyway, for those who want to see what they do in Linux, http://www.gelato.unsw.edu.au/lxr/source/mm/fadvise.c Pretty scary that Bruce said it could make older linuxes dump core - there isn't a lot of code there. » (ron mayer, 2006) But that seems a bit old. ---- Cédric Villemain Administrateur de Base de Données Cel: +33 (0)6 74 15 56 53 http://dalibo.com - http://dalibo.org
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