> > /* Retrieve next id in sequence: */
> > BEGIN;
> > SELECT id FROM id_allocator; /* This is the id to use */
> > UPDATE id_allocator SET id = id + 1;
> > COMMIT; /* Can't use the id until the transaction successfully commits!
> > */
>
> Just a side note; Traditionally this is done the other way around, i.e.
> update then select. The
> reason for this is the (small) window in the critical section for another
> session to issue the
> select at the same time causing a deadlock. Locking the table exclusively at
> the beginnng of the
> transaction avoids that problem.
True enough. You also need to do "BEGIN EXCLUSIVE;"
instead of begin. Or just handle the busy condition.
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