Connor McDonald <connor_mcdonald_at_yahoo.com> wrote in message news:<3E9E39BF.6878_at_yahoo.com>...
> > Your advice is appreciated.
>
> Hash joins are very senstive to the quality in the optimizer stats. As
> a result, the main drama you might encounter with hash joins is that
> they tend to go exponentially bad when you run out of memory, you end up
> with massive amounts of temp space used, and re-used, and re-used.
>
Yup, that's exactly what my concern is. I think hash join behaves
like sort - when you are out of memory, it does not "continue"
the operation to temp segment. It stops and copies the entire
momory to disk. This is worse than not having a large memory
to begin with. So to avoid this, I'd have to calculate well
to make sure it does not run out of hash_area_size.
Received on Thu Apr 17 2003 - 14:13:42 CDT
