On Monday 01 September 2008 11:30:58 Marc Cousin wrote: > On Monday 01 September 2008 08:51:48 Kern Sibbald wrote: > > Hello, > > > > Thanks for the patch. I see no problem applying it as it is a comment, > > which is a suggestion. However, as Eric has said, it may not be such a > > good idea for users to turn these indexes on since, as he points out, > > they will probably leave them. > > > > I like Eric's suggestion that dbcheck automatically (possibly with an > > option, or by requesting permission) create and then delete the indexes > > that are needed for speed. > > > > Or perhaps we can speed up dbcheck itself. The current SQL was written > > by me and is *far* from optimal. Marc Cousin has rewritten the dbcheck > > sql in a script file in <bacula-source>/examples/database/dbcheck.sql, > > which he says runs *much* faster. In the short run, I would recommend > > trying out this script. In the long run, when some developer steps > > forward, or we finish our 3.0.0 work, I would like to integrate his ideas > > into dbcheck. > > > > Please see more notes below ...
Thanks. I just added those notes to the script. > > The script version won't work better with mysql without indexes. > > The reason is that the script works with global queries instead of many > small queries like dbcheck. So PostgreSQL can optimise the query by > building hash joins or merge joins. > > Mysql can't do that (last time I checked, at least ...), and will do nested > loops between job and file for instance. And without the missing indexes, > mysql will still be as slow as with dbcheck, as you'll more or less have > thousands of full scans on the job table (where postgresql will do only a > few to build its hash). > > So for dbcheck with mysql, there is no other solution than adding the > missing indexes (but adding and dropping them just for the dbcheck is a > good option). > > ------------------------------------------------------------------------- > This SF.Net email is sponsored by the Moblin Your Move Developer's > challenge Build the coolest Linux based applications with Moblin SDK & win > great prizes Grand prize is a trip for two to an Open Source event anywhere > in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ > _______________________________________________ > Bacula-devel mailing list > Bacula-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/bacula-devel ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Bacula-devel mailing list Bacula-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-devel
