Dnia 16-12-2005, pią o godzinie 16:16 +1300, Mark Kirkwood napisał(a): > Craig A. James wrote: > > > > > What would be cool would be some way the developer could alter the plan, > > but they way of doing so would strongly encourage the developer to send > > the information to this mailing list. Postgres would essentially say, > > "Ok, you can do that, but we want to know why!" > > > > Yeah it would - an implementation I have seen that I like is where the > developer can supply the *entire* execution plan with a query. This is > complex enough to make casual use unlikely :-), but provides the ability > to try out other plans, and also fix that vital query that must run > today..... I think you could use SPI for that. There is function SPI_prepare, which prepares plan, and SPI_execute_plan, executing it. These functions are defined in src/backend/executor/spi.c. I think (someone please correct me if I'm wrong) you could prepare plan yourself, instead of taking it from SPI_prepare, and give it to SPI_execute_plan. SPI_prepare calls _SPI_prepare_plan, which parses query and calls pg_analyze_and_rewrite. In your version don't call this function, but provide PostgreSQL with your own plan (not-optimised according to PostrgeSQL, but meeting your criteria). -- Tomasz Rybak <bogomips@xxxxxxx>
