On Thu, 2002-04-25 at 00:46, mlw wrote: > We have had several threads about index usage, specifically when PostgreSQL has > the choice of using one or not. > > There seems to be a few points of view: > > (1) The planner and statistics need to improve, so that erroneously using an > index (or not) happens less frequently or not at all. > > (2) Use programmatic hints which allow coders specify which indexes are used > during a query. (ala Oracle) > > (3) It is pretty much OK as-is, just use enable_seqscan=false in the query. > > My point of view is about this subject is one from personal experience. I had a > database on which PostgreSQL would always (erroneously) choose not to use an > index. Are my experiences typical? Probably not, but are experiences like it > very common?
I have currently 2 databases that run with enable_seqscan=false to avoid choosing plans that take forever. > I don't know, but we see a number "Why won't PostgreSQL use my > index" messages to at least conclude that it happens every now and then. In my > experience, when it happens, it is very frustrating. > > I think statement (1) is a good idea, but I think it is optimistic to expect > that a statistical analysis of a table will contain enough information for all > possible cases. Perhaps we can come up with some special rules to avoid grossly pessimal plans. -------------------- Hannu ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/users-lounge/docs/faq.html
