Re: join removal

I started looking at this patch and it looks pretty good as far as it
goes. But I think we can do a lot more. It seems to me the cases where
foreign key relationships exist are likely to be really big use cases.

I have one big worry though. Currently you're detecting the unique
property using the planner's path mechanism. I suppose that works, but
it's only an accident of the planner design that the path for the
unique index will always be there if it's the join condition. My
instinct is that this code should be going back to the raw index info
to prove this property. The only practical effect I can think of is
that the plan will have to be marked as being dependent on that index
and that will be hard to do if you haven't identified a specific index
you're basing it on.

I would like to see a list of cases we plan to tackle preferably with
example queries, as a kind of checklist so we can knock them down one
by one. Right now it's unclear just how much of the problem space is
being solved.

Incidentally, guess what other database just got this feature committed...

http://askmonty.org/worklog/Client-BackLog/?tid=17

--
greg
http://mit.edu/~gsstark/resume.pdf