> And, to give you a starting point: the discussion has morphed into: 
> "What manual ways can we come up with for the DBA to 
> influence the planner and fix planner "bugs" which won't have 
> the fragility of query-based hints ala Oracle?"

I see a few downsides though:

1. it lacks a way to try out different plans in one session
        without actually influencing other sessions.
Maybe the way to do this is:
        begin work;
        add statistics hints
        explain analyze your select
        rollback work;
this is not enough to try a whole program with a new manual correction

2. To try out sensible plans would only work if there where ways that
allow all
nodetypes (on specific tables/where clauses) to be made more/less
expensive individually.

3. the manual entry may negatively influence other queries that
previously were fast
        thus a typical tuning measure for one bad query plan imposes
high risk  

4. sometimes I know as a developer that certain queries only run in case
abnormal skew in data (e.g. I expect to get a lot of rows even if
usually i would get few)


---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
       choose an index scan if your joining column's datatypes do not

Reply via email to