Sayan Biswas <formal.sayan@xxxxxxxxx> writes: > 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. The comment on standard_planner might help you: * Note to plugin authors: standard_planner() scribbles on its Query input, * so you'd better copy that data structure if you want to plan more than once. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
