On Fri, Nov 23, 2012 at 3:05 AM, Cédric Villemain <cedric@xxxxxxxxxxxxxxx> wrote: > Le mercredi 21 novembre 2012 17:34:02, Craig James a écrit : >> On Wed, Nov 21, 2012 at 5:42 AM, Kevin Grittner <kgrittn@xxxxxxxx> wrote: >> > It's a tough problem. Disguising and not documenting the available >> > optimizer hints leads to more reports on where the optimizer should >> > be smarter, and has spurred optimizer improvements. ... >> > Regarding the above-mentioned benefits we would stand to lose by >> > having clear and documented hints, perhaps we could occasionally >> > solicit input on where people are finding hints useful to get ideas >> > on where we might want to improve the optimizer. As far as worrying >> > about people using hints to force a plan which is sub-optimal -- >> > isn't that getting into nanny mode a bit too much? >> >> Toward that end, the hint documentation (which is almost always viewed as >> HTML) could be prefaced by a strong suggestion to post performance >> questions in this group first, with links to the "subscribe" page and the >> "how to report performance problems" FAQ. The hint documentation could even >> be minimalistic; suggest to developers that they should post their >> problematic queries here before resorting to hints. That would give the >> experts an opportunity to provide the normal advice. The correct hint >> syntax would be suggested only when all other avenues failed. > > We have hooks in PostgreSQL. We already have at least one extension which is > using that to change the planner behavior. > > We can have a bit more hooks and try to improve the cost estimate, this part > of the code is known to be built by reports and human estimations, also the > 9.2 version got heavy modifications in this area. > > Let the 'Hints' be inside an extension thus we are able to track them and fix > the planner/costestimate issues. > > I don't see why PostgreSQL needs 'Hints' *in-core*. Here here! PostgreSQL is well known for its extensibility and this is the perfect place for hints. That way they can get worked on without becoming a crutch for every user and forcing the backend developers to support what may or may not be a good idea syntax wise. After a few different people have banged some code out to make workable hint syntaxes for their own use maybe then it will be time to revisit adding hints to core. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
