Andrew Dunstan <andrew@dunslane.net> writes:
> Bruce Momjian wrote:
>> Also, Andrew, on your other patch for log_session_info line, Magnus had
>> the idea of giving each session an id based on the first transaction of
>> the session.
> I did think about using a cluster-wide sequence, if we can make such a
> thing (might also be useful for system generated UIDs too).
Not a good idea IMHO. If you do that, then there will be no such thing
as a purely read-only transaction, because *every* transaction will
include a nextval() call. That means even read-only transactions cannot
commit till the disk spins.
If we want a unique id for transient purposes like logging, then make
some kind of counter in shared memory. Don't use a sequence, it's much
too heavyweight.
regards, tom lane
