On Sat, Feb 21, 2015 at 2:09 PM, Peter Geoghegan <p...@heroku.com> wrote: > I can recreate the problem you see with text sort regressions. > Abbreviation is aborted for the case in question, unsurprisingly, and > fairly far in. With that many tuples, the idea of taking abbreviated > cardinality as a proxy for full cardinality becomes less important, > because either way you have to do at least 10 comparisons per item on > average.
Actually, it's closer to 20 comparisons past 1 million, on average. See my earlier 0002-* patch comments [1]. [1] http://www.postgresql.org/message-id/attachment/35861/0002-Estimate-total-number-of-rows-to-be-sorted.patch (search for "20") -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
