Simon Slavin wrote: > On 18 Nov 2009, at 7:15pm, priimak wrote: > > >> I see. However, the problem is related to journal been named after the >> database name. >> That should not be a problem if I use symlink to access database for >> reads only and >> actual db file name for updating, isn't? >> > > If you use a symbolic link for a database file, there's some doubt about > where the journal file belongs. The documentation says > > "The rollback journal is always located in the same directory as the database > file and has the same name as the database file except with the 8 characters > "-journal" appended." > > The problem is that there's no way for sqlite to tell that your symbolic link > is not the real database file. So it could create the journal file in the > directory containing the link rather than the directory containing the actual > database. And if another application opens the database directly rather than > using the link, it will not find the journal file, so it will not deal with > anything needing the journal file correctly. This is mentioned in section 6 > of > > <http://www.sqlite.org/lockingv3.html> > > If that documentation is right, then for symbolic links, that might be > considered a bug in sqlite. It should be possible to do a 'resolve links' on > the file specification before deciding where to create the journal. On the > other hand, for hard links this is not possible: the hard linking system does > not have a 'real' location for the file and other pointers to it, instead > each link to the file is equally valid. But either way it is documented that > you shouldn't use links. I understand that. However, that would not present a problem if I access database by its symlink for reading only and database directly if I am updating isn't? By the way the reason for that usage ( though there are work arounds ) is that I keep two instances of db file a.db.1 and a.db.2 with symlink a.db pointing to one or there db file. If a.db -> a.db.1 I apply update to a.db.2, swap symlink and then update a.db.2. Symlink a.db used by webapp, which performs *only* select queries. And yes, I do have a.db.1-journal and a.db.2-journal files, but not a.db-journal
That seems safe, isn't? -- Dmitri Priimak _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
