On 3 Jul 2015, at 2:31pm, Mikael <mikael.trash at gmail.com> wrote: > Wait, so if connection 1 is doing VACUUM and connection 2 attempts > INSERT/UPDATE/DELETE and connection 3 attempts SELECT all concurrently, > what happens and how ACID will the DB be?
VACUUM locks the database, just like INSERT and UPDATE. Other writing operations will be forced to wait until the VACUUM is complete and the database is unlocked again. Depending on your settings and journal mode, read operations will (I believe) read the uncommitted changes from the 'old' copy of the table, or will be delayed until the VACUUM is complete. Whichever it is, they should get correct data. Of course, waiting for VACUUM may take far longer than waiting for a single INSERT or UPDATE, which is why you need a longer timeout setting than just a few seconds. Simon.
