> 1. Doing a vacuum immediately after the import isn't useful, there is > nothing to vacuum by definition.
While this is true an ANALYZE should still be done to initialize the statistics. > 2. Doing a vacuum after a diff is also useless, since the vacuum will > probably takes much much longer than applying the diff. (This I noted > when appliyng an empty diff took minutes on my machine). If you leave > it in you won't be able to apply diffs fast enough. I will have to disagree here (and agree with Jochen): >From the documentation[1]: > 1. To recover or reuse disk space occupied by updated or deleted rows. Which in my opinion _only_ makes sense after a diff as it is the only time anything is updated or deleted. Depending on the type of diffs (minute, hour, daily) of course. I import the daily diffs and schedule a VACUUM ANALYZE after each import. > 2. To update data statistics used by the PostgreSQL query planner. Very important, too, depending on the type of queries you run. For me it is a lot of work on the tags tables. On a related note: There was a change between PostgreSQL 8.3 and 8.4 which increased the default_statistics_target from 10 to 100 and its maximum from 1.000 to 10.000 which makes ANALYZE runs take longer but at least for me it helps a lot. Cheers, Lars [1]: http://www.postgresql.org/docs/8.4/static/routine-vacuuming.html _______________________________________________ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
