On Thu, 2008-06-26 at 12:36 -0400, Robert Haas wrote: > > IMHO we should have a single parameter which indicates how much planning > > time we consider acceptable for this query. e.g. > > > > optimization_level = 2 (default), varies 1-3 > > > > Most automatic optimisation systems allow this kind of setting, whether > > it be a DBMS, or compilers (e.g. gcc). > > It's my understanding that the philosophy of the PGDG in the past has > been to avoid putting any kind of hints into the system, focusing > rather an improving the planning of queries.
It's not a specific hint, its a general goal setting. Providing information to the optimizer about our goals is not a universally bad thing; telling it to force a particular plan against its better judgement probably is. For example, gcc has exactly this kind of optimization mode. -O2 should be acceptable to us, but an option like -fsplit-ivs-in-unroller probably isn't. > If one were to add a hint, I think the hint should tell the planner: > Hey, see this left join? Now that *is* a hint. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
