On Wed, Jun 9, 2010 at 11:26 AM, Jay A. Kreibich <j...@kreibi.ch> wrote:
> On Wed, Jun 09, 2010 at 01:40:30PM +0100, Simon Slavin scratched on the > wall: > > > > On 9 Jun 2010, at 9:48am, Wei Kai wrote: > > > > > I have a problem here. As we know sqlite creates a journal every time a > > > write transaction happens. On a flash file system, when a write to > database > > > failed because of the lack of enough disk spac > > > > Sorry, but if your program crashes because you ran out of disk space, > > you're out of luck. There's no way to have a program recover from > > the situation because you have no space to put the recovered > > information in. You need an intelligent human to decide what can > > be deleted. > > I think the point he was making is that a developer cannot assume > writing data to the middle of an existing file will not return an > out-of-space error. > > I'd be very surprised if SQLite makes any such assumptions, however. > SQLite makes no such assumption. On the other hand, if SQLite is unable to rollback a failed transaction, then it is stuck until the error is resolved. Until sufficient space becomes available on the device to complete the rollback, the database will be unreadable. There isn't much one can do about this when using a rollback journal. The problem does not come up with http://www.sqlite.org/draft/wal.html - the database continues to be readable after a failed checkpoint. > This condition is hardly unique to flash filesystems. Journaled > filesystems can have the same issue, as do sparse files (although I > doubt SQLite would ever create a sparse file). Reallocation of > blocks and automatic defragmentation can also contribute to > similar issues. > > > If you are concerned about this situation, make a file called > > 'wasteofspace' which takes up 10 kilobytes of space. When you > > need emergency space to recover from a crash, delete this file. > > That's not necessarily useful. See above. > > -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 > 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
