On Mon, Aug 04, 2008 at 05:19:50PM -0400, Robert Treat wrote: > See, this is what we ended up talking about before. Someone will say "I'd > like > to prevent my devs from accidentally doing queries with cartesian products" > and they will use this to do it... but that will only work in some cases, so > it becomes a poor tool to solve a different problem. > > BTW, what I really love about statement costs, is that they aren't even > reliable on the same machine with the same data. I have seen query plans > which run on the same data on the same machine where the resultant query > runtime can vary from 2 hours to 5 hours, depending on how much other > concurrent traffic is on the machine. Awesome eh?
Sure, I don't think anyone believes that costs are precise. But the case that is interesting is 2 hours versus years and years. > The footgun in my mind is that people will think this solves a number of > problems even though it doesnt solve them well. However, the footgun for yo I suspect that a good solution to this problem is impossible as it is more or less the halting problem. So I'm willing to accept a poor solution based on costs and then hope we improve the cost model. -dg -- David Gould [EMAIL PROTECTED] 510 536 1443 510 282 0869 If simplicity worked, the world would be overrun with insects. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
