On Sun, Oct 18, 2009 at 3:57 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> You could probably convince me that a merge join is not going to be
>> too useful (how often can you want a merge join on the inner side of a
>> nested loop?
>
> Why not? As Andrew pointed out, what we're really trying to accomplish
> here is consider sub-join plans that are parameterized by a value
> obtained from an outer relation. I think we shouldn't artificially
> limit what we consider.
>
> But anyway I think we're on the same page here: what we ought to do is
> try implementing this scheme without any extra restrictions on what it
> considers, and see what the performance is like. We can try to limit
> what it considers if it turns out not to work well in the simplest
> form.
And then when we get done we can consider implementing $SUBJECT, which
is no longer what this thread is about at all. :-)
...Robert