Modifying Postgresql Optimizer to select optimal memory

Hello everyone,

We are currently working on a DBMS course project that requires us to
modify postgresql optimizer. We need to vary work_mem within a range and
note down the cost at those points(allocated memory) after 'explain'
operation and then select the optimal tradeoff. We were changing
"postgresql-9.1.12/src/backend/optimizer/plan/planner.c" where we created a
new function mem_tradeoff() that calls planner() within a for loop for the
varying memory. This mem_tradeoff() is called from pg_plan_query() in
"postgresql-9.1.12/src/backend/tcop/postgres.c". The problem is, if the for
loop runs only one iteration, everything is fine, but if we print
plan->planTree->total_cost, it is printed 132 times for any query. Also if
the for loop runs more than one iteration, we get a segmentation fault. Any
help is very much appreciated.

Thank you,
Sayan

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Don't kill the dream - execute it.