* Dumb Optimization #1:
- Add executorFunc function pointer to struct PlanState
- in ExecProcNode.c -> ExecProcNode() :- upon first execution, set executorFunc to the function corresponding to
node type- next calls use function pointer
Effect : removes a switch (nodeTag(node)) which otherwise executes for
every tuple returned by every node
Gain :
- 4% CPU time on SELECT sum(an integer column) FROM a table of one million
rows
- nil on selects returning few rows obviously