On Wed, Feb 23, 2005 at 10:02:22AM +1100, Neil Conway wrote: > Kenneth Marshall wrote: > >GEQO is an attempt to provide a near-optimal join order without using > >an exhaustive search. "An exhaustive, deterministic search of a subset > >of the search space" has a non-zero probability of finding only a local > >minimum in execution time. > > I'm not sure what you mean. By an "exhaustive, deterministic search of a > subset of the search space", I was referring to using the normal > planner, but restricting the search space to only left-deep plans. Since > GEQO will also only consider left-deep plans, ISTM there is no issue of > "local minima" that does not apply to an equal degree to GEQO itself.
That is just a direct quote from your text. That is true, that this will have the same "local minima" problem as GEQO. > > >Since purely random selection, with learning, works so well, it may be > >worth developing a new random join-order optimization algorithm > > Yeah, I agree. I've read a few papers on randomized algorithms for join > order selection, but none of them really seemed to be clear winners. Do > you have a reference for the paper you read? > Here is one article that I found relevent in my literature search to find research on join-order optimization. It is appealing in that it should be fairly straightforward to implement and would allow us to consider bushy plans: http://www.cwi.nl/htbin/ins1/publications?request=pdfgz&key=WaPe:BNCOD:00 Ken ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
