Stephen Frost <sfr...@snowman.net> writes: > * Tom Lane (t...@sss.pgh.pa.us) wrote: >> A variant idea would be to replace the exact cost comparison with a >> second round of fuzzy cost comparison, but with a much tighter fuzz >> factor, maybe 1e-6 instead of 0.01.
> Not impressed with this idea- the notion that our model is good enough > to produce valid values out to that many digits is, well, unlikely. While I remain convinced of the abstract truth of that position, I've committed a patch that uses a second round of fuzzy comparison. It turned out that simply removing the exact comparison as per my first proposal resulted in a surprisingly large number of changes in the regression test results; apparently, a lot more cases than we realized have multiple plans with indistinguishable costs. I didn't feel like going through and validating the test result changes, and besides that this could have resulted in changes in behavior-in-the-field that people would complain about. 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