Re: left-deep plans?

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.

> 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?

-Neil