Angus March <an...@uducat.com> wrote: > Yes, I see. So what is key to the problem is that someone tries to > change their read lock to a write lock. I guess I just thought that > the kernel that manages fcntl() would have a way of dealing with > this. Can this situation not be averted if at step 3, transaction A > releases its read lock before requesting a write lock?
Then it wouldn't be much of a transaction, now would it? Imagine the classic example, where a transaction first verifies that the balance in a bank account is sufficient, then performs a withdrawal. If it relinquishes all locks between these two steps, then somebody else may record a withdrawal from that account, so that the write operation would then make the balance negative, thus violating an invariant. Of course, if that's what the application wants, it can simply perform the read and the write operations in two separate transactions. Igor Tandetnik _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
