"David Parker" <dparker@tazznetworks.com> writes:
> I know from the documentation that the FOR implicitly opens a cursor,
> but I'm wondering if there would be any performance advantages to
> explicitly declaring a cursor and moving through it with FETCH commands?
AFAICS it'd be exactly the same. Might as well stick with the simpler
notation.
> I have to use the ORDER BY, so I imagine I'm taking the hit of
> processing all the records in the table anyway, regardless of how many I
> ultimately fetch.
Not if the ORDER BY can be implemented using an index. Perhaps what you
need is to make sure that an indexscan gets used.
> The nature of the data is that chunksize doesn't necessarily match up
> one-for-one with rows, so I can't use it as a LIMIT value.
Can you set an upper bound on how many rows you need? If you can put a
LIMIT into the select, it'll encourage the planner to use an indexscan,
even if you break out of the loop before the limit is reached.
regards, tom lane