Florian G. Pflug wrote: > Gavin Sherry wrote: > >On Mon, 24 Jul 2006, Golden Liu wrote: > > > >>begin; > >>declare foo cursor for select * from bar for update; > >>fetch foo; > >>update bar set abc='def' where current of foo; > >>fetch foo; > >>delete from bar where current of foo; > >>commit; > > >No one has stepped up to do this for 8.2 so unfortunately you will most > >likely not see this within the next year or so :-(. > > Couldn't this be emulated by doing > begin; > declare foo cursor for select * from bar for update; > fetch foo into v_foo ; > update bar set abc='def' where ctid = v_foo.ctid; > fetch foo into v_foo ; > delete from bar where ctid = v_foo.ctid; > commit; > > Or could a concurrent vacuum run lead to the wrong > rows being updated/deleted?
No, a concurrent vacuum can't change that because vacuum can't change the page unless it can get a super-exclusive lock on it (which means nobody else can have a scan stopped at that page, which is exactly what this cursor has). -- Alvaro Herrera http://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
