Is it a reasonable idea to add a counter to set_cheapest? I think this function evaluate the cheapest path. Therefore, it means how many complete plans have been considered, doesn't it?
2009/10/12 纪晓曦 <sheep...@gmail.com> > What I want to count is the number of plans that have been considered > cheapest_path. Since if a path is considered to be a cheapest_path, the > postgres optimizer need to spent time on comparison. I think this is what I > want. > > 2009/10/4 Martijn van Oosterhout <klep...@svana.org> > >> On Sat, Oct 03, 2009 at 04:20:59PM +1000, ????????? wrote: >> > Since I also need to consider gego, is this the best way to do it? >> >> I think you need to be clearer about what you're trying to count. >> Consider a nestjoin plan where: >> >> - For the inner side it considers 7 paths and throws away 4. >> - For the outer side it considers 6 paths and throws away 2. >> >> Do you want the number 3*4=12 or 7*6=42? Or something in between (what >> if in addition to a nestjoin plan otther possibilities are possible). >> >> As you can see, you can't talk about complete plans because they don't >> exist until right at the end, until then it's just considering how to >> combine different paths in sensible ways. >> >> Have a nice day, >> -- >> Martijn van Oosterhout <klep...@svana.org> http://svana.org/kleptog/ >> > Please line up in a tree and maintain the heap invariant while >> > boarding. Thank you for flying nlogn airlines. >> >> -----BEGIN PGP SIGNATURE----- >> Version: GnuPG v1.4.9 (GNU/Linux) >> >> iD8DBQFKyIiaIB7bNG8LQkwRAklcAJsFBOQE/xAscZm0ok4WwxVh+C6x8ACfYuNz >> G4GpDdQ4IuTXGWc5QHhD5dc= >> =ynTH >> -----END PGP SIGNATURE----- >> >> >
