Re: *_collapse_limit, geqo_threshold

Dimitri Fontaine <dfontaine@hi-media.com> writes:
> Another idea would be to have more complex metrics for deciding when  
> to run geqo, that is guesstimate the query planning difficulty very  
> quickly, based on more than just the number of relations in the from:  
> presence of subqueries, UNION, EXISTS, IN, or branches in where  
> clause, number of operators and index support for them, maybe some  
> information from the stats too...

Pointless, since GEQO is only concerned with examining alternative join
orderings.  I see no reason whatever to think that number-of-relations
isn't the correct variable to test to decide whether to use it.
        regards, tom lane