On Mon, May 17, 2010 at 02:15:09PM -0400, Sam Carleton scratched on the wall: > Michael, > > I really don't mean to be rude, but I know about the SQLITE_BUSY and that it > must be handled and all that good stuff, am I handling it right now? No; > will I? Yes, but that isn't my issue, I understand I need to handle those > conditions and I am confident that I know how to handle that condition.
> My question is real simple: Can I open a DB in read-only and then attach a > :memory: db to it and write to the :memory: db? Or must the file DB be > opened in read/write? No; Yes. Whatever flags are passed to sqlite3_open_v2() appear to be passed to all ATTACHed databases as well, so if you open a database with SQLITE_OPEN_READONLY, the :memory: db is read-only as well. This limits their use. If you open a database read-write, but the file permissions do not allow that, it will still be opened read-only. ATTACHed DBs will open read-write as well. However, if the main db is in a read-only directory, SQLite can't make the proper journal files and returns errors. > Oh, more to your question, let me ask you if this following assumption is > correct: > > *If you only need read-only access, open it in read-only, fore it plays > nicer with other threads that are also doing read-only operations.* Not really. Even if the DB is opened read-only, it still needs to manipulate locks on the file. You might still get SQLITE_BUSY or any other lock-related errors/conditions. -j -- Jay A. Kreibich < J A Y @ K R E I B I.C H > "Our opponent is an alien starship packed with atomic bombs. We have a protractor." "I'll go home and see if I can scrounge up a ruler and a piece of string." --from Anathem by Neal Stephenson _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
