Thanks for the thorough explanation, Rowan. I must say I learned something, myself!
On November 23, 2017 11:23:11 PM EST, Rowan Worth <row...@dug.com> wrote: >On 24 November 2017 at 10:27, J. King <jk...@jkingweb.ca> wrote: > >> The rollback journal is used to return the database to its previous >state >> in the case of a partial write, not complete writes which are >interrupted. >> As you didn't commit the transaction, no write occurred, never mind a >> partial one, so the database remained in its initial state. >> >> Deleting a rollback journal is a bad idea. In this case it was >harmless, >> but normally it's an excellent way to corrupt your database. >> >> As to where uncommitted transactions live, I am not sure. I'll let >someone >> else answer that. >> > >When a database page is modified during a transaction, the initial data >is >written to the rollback journal and the modified data is held in memory >until COMMIT or the transaction memory cache is exceeded (see PRAGMA >cache_size). > >If either of those happen, sqlite obtains an EXCLUSIVE lock on the >database >and starts writing the modified data (after making sure the rollback >journal is properly synced to disk). At this point you have a partially >committed transaction and the DB is not necessarily consistent (which >is >why it's done under an exclusive lock, and why deleting the rollback >journal is a terrible idea as you said). > >In the case of COMMIT this is just a matter of I/O (syncing the DB and >deleting the rollback journal) and should be fairly quick. But in the >case >of a cache spill, this partially committed state can be observed for >much >longer, depending on the size of the transaction. > >-Rowan >_______________________________________________ >sqlite-users mailing list >sqlite-users@mailinglists.sqlite.org >http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users -- Sent from my Android device with K-9 Mail. Please excuse my brevity. _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
