Robert Haas <robertmh...@gmail.com> writes: > One possibility would be to remove join_collapse_limit entirely, but > that would eliminate one possibily-useful piece of functionality that > it current enables: namely, the ability to exactly specify the join > order by setting join_collapse_limit to 1. So one possibility would > be to rename the variable something like explicit_join_order and make > it a Boolean; another possibility would be to change the default value > to INT_MAX.
As the person who put in those thresholds, I kind of prefer going over to the boolean definition. That was the alternative that we considered; the numeric thresholds were used instead because they were easy to implement and seemed to possibly offer more control. But I'm not convinced that anyone has really used them profitably. I agree that the ability to use JOIN syntax to specify the join order exactly (with join_collapse_limit=1) is the only really solid use-case anyone has proposed for either threshold. I'm interested in Andreas' comment that he has use-cases where using the collapse_limit is better than allowing geqo to take over for very large problems ... but I think we need to see those use-cases and see if there's a better fix. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers