> The problem I try to solve is something along: a bunch of clients try
to update a count, and ONE of them must initialize > the count if it
does not exist... this can't be done with current infrastructure without
race conditions.
The solution without merge but a unique key in other db's is:
update
if no rows updated
insert
if duplicate key
update
if no rows updated goto insert
note, that the counter updates need to be of the form set x = x + ?
where key=y
do you see a potential race condition with this ?
In pg you also need a savepoint before the insert for this to work.
Depending on the ratio of insert vs update we also start with insert
when
the insert succeeds more that 50% (I would use a higher percentage with
pg though):
insert
if duplicate key
update
if no rows updated goto insert
Andreas
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