On Tue, Apr 30, 2013 at 4:35 PM, Ryan Johnson <ryan.john...@cs.utoronto.ca>wrote:
> On 30/04/2013 12:59 PM, Richard Hipp wrote: > >> On Thu, Mar 14, 2013 at 2:07 PM, Ryan Johnson >> <ryan.john...@cs.utoronto.ca>**wrote: >> >> Hi all, >>> >>> I'm running sqlite-3.7.13 on cygwin. Playing around with various TPC-H >>> queries with my class recently, I hit a strangely slow query and don't >>> understand why it's so slow. >>> >>> >>> http://www.sqlite.org/draft/**queryplanner-ng.html<http://www.sqlite.org/draft/queryplanner-ng.html> >> > Nice. If you're willing to do quadratic work anyway, would it make sense > to try and establish upper/lower bounds on the optimal solution to decide > how much harder to work? I believe it's possible to find lower bounds for > TSP using minimum spanning trees, and that computing the MST should be > log-linear in the number of joins for most queries; if the "easy" NN=1 > solution isn't too much higher than the lowest of a random selection of > upper bounds, it's probably safe to stop looking; if the best upper bound > is a *lot* lower (like the NN=1 result for Q8 being 14,000 times slower > than the optimal), it probably justifies investing more time with an NNN > search for that particular query, in hopes of bringing down the predicted > runtime; the expected time difference could even be used to set the NNN > factor... > Yes - there are countless tricks like this you can use to make it go faster. Be assured that I will be trying them all out. -- D. Richard Hipp d...@sqlite.org _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
