On Thursday May 20 2004 8:19, Jeff Davis wrote: > > create table products ( > id serial primary key, > ... > ); > > create table cart_items ( > id serial primary key, > cart_id int references ..., > prod_id int references product(id), > quantity int > ); > > The problem is, when you add the first item to "cart_items" you have to > do an INSERT with a quantity of 1, but after that you need to do > UPDATEs. That would seem to create a potential race condition, so in > order for that to work it would seem you would need to do an ACCESS > EXCLUSIVE lock on the table to make sure no other process was reading > the table at the same time. I'm not sure what potential race condition you see since you haven't said much about how your transactions fit in here. But I would suggest you go with your first design and don't worry about any explicit locking unless/until it clearly becomes a problem. I've built numerous things similar to this, and in my experience, PostgreSQL is very good about managing the locking in an intelligent manner if your transactions are reasonably grouped. HTH. ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
