> From: Kai Krueger [mailto:kakrue...@gmail.com] > Subject: Re: [OSM-dev] osm2pgsql slow slim import > > Anyway, as Frederik suggested, I have changed osm2pgsql to automatically > set the parameter synchronous_commit to off for the import session. > > Doing this should be safe. Unlike turning off fsync, turning of > synchronous_commit can not lead to a corrupted database. All that can > happen is that a few transactions that osm2pgsql though were processed > might get lost on a database crash. During a full import that is "fine" > as there is no way to recover from a partial import anyway and one needs > to start from scratch. However, it should also be fine during diff > imports, as it will simply mean some pending ways that were processed > did not get mark as done and will be re-processed on the next diff > import. > > Hopefully this therefore fixes the performance regression introduced > previously. >
I also researched this and came to the same conclusions that synchronous_commit=off is fine for the similar application of pgsnapshot (see http://www.paulnorman.ca/blog/2011/11/loading-a-pgsnapshot-schema-with-a-pla net-take-2/) for both the initial import and diff processing. I also think fsync=off is safe for the initial import if you're prepared to drop everything if you crash. _______________________________________________ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
