On 11 Dec 2014, at 10:08, Dan Kennedy wrote: > On 12/11/2014 05:49 AM, Nick wrote: >> On 10 Dec 2014, at 07:35, Dan Kennedy wrote: >> >>> Strictly speaking the database file may not be well-formed even if there is >>> no ongoing checkpoint. If: >>> >>> a) process A opens a read transaction, >>> b) process B opens and commits a write transaction to the database, >>> c) process C checkpoints the db, >>> >>> then the db file considered without the *-wal file may be corrupt. The >>> problem comes about because process C can only checkpoint frames up until >>> the start of B's transaction. And there is an optimization that will >>> prevent it from copying any earlier frames for which there exists a frame >>> in B's transaction that corresponds to the same database page. So it >>> effectively copis only a subset of the modifications made by earlier >>> transactions into the db file - not necessarily creating a valid db file. >> Can this corruption be detected by running PRAGMA quick_check / >> integrity_check? Having the occasional backup db corrupted would be >> tolerable. > > In many cases, but not generally. There would exist cases where a part of a > committed transaction was lost, or the values in unindexed columns where > replaced, that sort of thing.
Ok. Presumably a SQLITE_CHECKPOINT_FULL or SQLITE_CHECKPOINT_RESTART checkpoint mode would ensure the db file is valid? Regards Nick _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
