On Thu, Nov 29, 2012 at 02:39:49PM +0000, Black, Michael (IS) scratched on the wall: > I thought a backup was using a snapshot and locking the database?
No... the source DB remains available. That's largely the point of the API. In fact, the full name is the "Online Backup API." The fact that it can also be used to copy in-memory DBs is more of a side benefit, even if it was a much needed benefit. http://www.sqlite.org/c3ref/backup_finish.html SQLite holds a write transaction open on the destination database file for the duration of the backup operation. The source database is read-locked only while it is being read; it is not locked continuously for the entire backup operation. Thus, the backup may be performed on a live source database without preventing other database connections from reading or writing to the source database while the backup is underway. If the source database is modified by the same connection doing the backup, the page updates are written to both DBs. If the source DB is modified by any other connection, the backup automatically restarts. Because it is easy to imagine a case when the backup gets caught in a restart loop, some people choose to make the backup a more atomic operation by having the backup "step" function copy all the pages in one go. In that case it is likely that the majority of pages are written out in-order, but I wouldn't want to bank on that. -j -- Jay A. Kreibich < J A Y @ K R E I B I.C H > "Intelligence is like underwear: it is important that you have it, but showing it to the wrong people has the tendency to make them feel uncomfortable." -- Angela Johnson _______________________________________________ sqlite-users mailing list [email protected] http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
