Well, I'm a relative newbie to SQL, but I have been told that this behaviour
is a bug. I hope I didn't misunderstand something.
To reproduce, first create a table 'counters' that looks like that:
counter1
----------
0
(1 row)
Then execute the following commands parallelly on two psql terminals:
set transaction isolation level serializable;
begin;
update counters set counter1=(select counter1+1 from counters);
(The second psql terminal will not return from executing the last statement)
Commit on both terminals, then do a select again. The result will be:
counter1
----------
1
(1 row)
Oops! ;-)
If instead I use an update statement like that:
update counters set counter1=counter1+1;
psql behaves like expected, i.E. the result is 2.
--
Grüße,
Nico
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