All paths of optimizer are just in function "standard_planner", which
mainly calls "subquery_planner", which just takes the rewrited
structure "Query" as the main parameter. But system provides another
way if you wannt to write your own optimizer, that is: define the
global var "planner_hook" to your own optimizer function (please refer
to function "planner"). So this is one of the way prevents the system
takes it own optimizer routine.
If you want to modify the plan returned by the optimizer, you can
add some code just in the function "planner", i.e., takes result as the
param of your routine.
Any way, It is needed that you get very familiar with the structure of "PlannedStmt".
**********************************************************************
2008/6/3 John Cieslewicz <johnc@xxxxxxxxxxxxxxx>:
I completely understand that what I am proposing is somewhat mad and I didn't expect it to be easy.
Basically, I'm doing some research on a new operator and would like to
start testing it by inserting it into a very specific place in very
specific plans without having to do too much work in plan generation or
optimization. I think that I could do this by writing some code to
inspect a plan and swap out the piece that I care about. I realize this
is a hack, but at the moment it's just for research purposes. Though I
have worked with the internals of other db systems, I'm still getting
familiar with postgres. Could such a piece of code be placed in the
optimizer just before it returns an optimized plan or can a plan be
modified after it is returned by the optimizer?
John Cieslewicz.
