printing the query plan?

Hi,

I want to print the query-plan that will be used before the execution of the query. Therefore put this line at the beginning of the ExecutorStart() function located in execMain.c :

print_plan(queryDesc->plantree,queryDesc->parsetree);

However, it did not work. What I want to ask is:

1. Does postgresql call ExecutorStart()-ExecutorRun-ExecutorEnd functions each time a new query is invoked? If so, why the above line did not work?

2. Can I print just a dummy string inside ExecutorStart() function and will it be shown before the result of the query? Because I also tried this and it also did not work.

Thanks  a lot.

Baran