On 19 Oct 2012, at 9:40pm, Efim Dyadkin <efim.dyad...@pdgm.com> wrote:
> You are right about the purpose of unlink but it is out of context. There are > a transaction in progress and hot journal on disk. If journal can't be > deleted by the end of transaction, the transaction can't be considered to be > successfully finished. This is not correct. SQLite does not close the journal file at the end of every transaction unless you have only a single connection to the database and the journal mode set to DELETE, and that is not common these days because creating and deleting files is so slow. The times you should see a journal file deleted is when all connections to the database have been closed: you've done a _close() for every _open(). <http://www.sqlite.org/pragma.html#pragma_journal_mode> You can ignore things like journal files, which file data is stored in, and where in the file it's stored. SQLite should be creating and deleting its own files as it sees fit, and if you create, edit or delete any of them yourself then you can consider your database to be potentially wrong or corrupt. Don't mess with any SQLite files. > But current implementation of Sqlite considers this transaction as > successfully committed! This is how to know that a transaction is finished: you execute the SQL command "COMMIT" and the function call returns with the code SQLITE_OK rather than an error. If this has happened, the transaction is successfully committed. Whether you happen to notice files on disk being created, resized, deleted or deletable is useful for monitoring whether database connections are open, but not to individual transactions. > The problem with file system going down during a transaction is a real > problem that occurred to our customers. For them it was absolutely a disaster > because they lost data they had successfully saved. If the file system goes down /during/ a transaction, your application did not save data. Your application's user interface should not be indicating to the user that data is saved during a transaction. It should do that only once the "COMMIT" is reported successful. Simon. _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
