On Sun, Feb 1, 2009 at 12:03 PM, David Fetter <da...@fetter.org> wrote: > On Sat, Jan 31, 2009 at 11:37:39PM -0500, Robert Haas wrote: >> I've been doing some benchmarking and profiling on the PostgreSQL >> query analyzer, and it seems that (at least for the sorts of queries >> that I typically run) the dominant cost is add_path(). I've been >> able to find two optimizations that seem to help significantly: > > Are there any cases you've found where this change significantly > impairs performance, and if so, how did you find them? If not, would > you be up for trying to find some?
Basically, the patch is just performing the same operations with less overhead. For example, add_similar_path() is pretty much the same thing as repeated calls to add_path(), but you save the cost of unnecessary pathkey comparisons and maybe some ListCell alloc/free cycles. So I'm not really sure how it could make things worse, but I'd be interested in knowing if there's a case that you're worried about. It's pretty low-level code, so I don't think there's room for a lot of surprises. ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
