On Wed, Nov 30, 2011 at 1:21 PM, Black, Michael (IS) <michael.bla...@ngc.com > wrote:
> Maybe we need a "pragma wal_trim" ?? This would automatically trim it > after a checkpoint? Or make it an explicit action? > checkpoint cannot trim. This is because of the rule that checkpoints will never block either readers or writers, and a trim operation requires getting a write lock, and hence as the potential to block writers. That's why the trim is done by the next writer - since it already has to get a write lock and hence has already dealt with any concurrency issues. > > > > Waiting for another write before truncating it seems too late and not a > logical thing to expect. > > > > > > Michael D. Black > > Senior Scientist > > Advanced Analytics Directorate > > Advanced GEOINT Solutions Operating Unit > > Northrop Grumman Information Systems > > ________________________________ > From: sqlite-users-boun...@sqlite.org [sqlite-users-boun...@sqlite.org] > on behalf of Richard Hipp [d...@sqlite.org] > Sent: Wednesday, November 30, 2011 12:10 PM > To: Teg; General Discussion of SQLite Database > Subject: EXT :Re: [sqlite] WAL file size > > On Wed, Nov 30, 2011 at 1:04 PM, Teg <t...@djii.com> wrote: > > > Hello Richard, > > > > When does the WAL get trimmed down? If my transaction completes, does > > the WAL file get deleted? I've seen the WAL grow to 4 times my actual > > DB size so, I don't really want 160 Gigs of WAL hanging out when the > > process that generated it is only run once a month. > > > > SQLite starts writing the WAL file from the beginning again on the first > write transaction that follows a checkpoint that ran to completion and > where there are no readers using the WAL file. A checkpoint will normally > run to completion if there are no readers still using prior transactions. > If there are readers on prior transactions, then the checkpoint cannot run > to completion since that would delete content out from under the readers. > > > > > -- > D. Richard Hipp > d...@sqlite.org > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > -- D. Richard Hipp d...@sqlite.org _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
