whether I can see other alternative plantrees for one query?

hi, all
NOTE: Version is 8.4 Fedora 20 X86_64

for understanding optimizer's internals, I

*set debug_print_plan=on*

and created two tables as follows :

*create table Reserves (sid integer, bid integer,day date,rname
char(25));create table Sailors(sid integer,sname char(25),rating
integer,age real);*

and add 1,000,000 records for each.

and execute the cmd:

*select S.rating,count(*) from Sailors S where S.rating > 5
and S.age = 20 group by S.rating;*

but from the log, I only found the final selected planTree, so I want to
ask:
what should I do if I want to see the other alternative planTrees? any
advice will be apprecitaed!

Dillon Peng