But it's of zero size, so there cannot be anything inside. As far as I have understood, it's just a journal containing the changes since the last checkpoint. If I don't change anything, why should there be the need of this journal? I would expect the journal to be created when the first write operation (INSERT, DELETE, whatsoever) occurs, but not for a read operation.
And moreover, why is read-only-mode allowed to create a journal (this is contradictory to the read-only-idea), but not delete it upon closing the connection? Actually, this leads to more problems: If the database itself has the read-only-attribute set (by filesystem or ACL), SQLite would start journaling changes which can be never be checkpointed. In commonsense, a write operation should immediately terminate and return an error in this case. Finally, I have noticed the immutable mode, but I have a bad feeling about it. If I understand correctly, a second connection could still open the same database in write-mode. I would instead expect that a read-only-connection locked the database (using file locking mechanism) and a parallel write-connection to be blocked until the locked is released. (No temporary files should be required until this moment.) ----- Original Message ----- From: Shawn Wagner <shawnw.mob...@gmail.com> To: SQLite mailing list <sqlite-users@mailinglists.sqlite.org> Sent: Sunday, March 24, 2019, 11:29:58 Subject: [sqlite] read-only database in WAL mode and temporary files Even a read only database needs to create the wal journal if it doesn't exist at the moment for a database that uses that mode: https://www.sqlite.org/wal.html#read_only_databases You might look into the immutable option mentioned there and see if it's appropriate for your needs. On Sun, Mar 24, 2019, 2:33 AM Thomas Kurz <sqlite.2...@t-net.ruhr> wrote: > When I open a database in read-only mode (?mode=ro), I observe that the > WAL and SHM temporary files are created anyway. Is there any possibility to > prevent the creation of these files? Aren't they useless? > Even worse (using sqlite3.exe version 3.27.1): > .open test.db > pragma journal_mode=wal; > create table a (b integer); > insert into a (1); > .quit > This creates database with WAL and SHM files; those files are correctly > removed when exiting. > .open --readonly test.db > select * from a; <--- creates WAL and SHM -- why? > .quit > Now, WAL and SHM files aren't deleted anymore. > Proposal: Neither WAL nor SHM should be created at all when opening a > WAL-mode database in read-only mode. > _______________________________________________ > sqlite-users mailing list > sqlite-users@mailinglists.sqlite.org > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
