CS3223 2013
Assignment 1: Implement LRU replacement algorithm to replace CLOCK algorithm currently used in PostgreSQL.
The implementation approach is using double linked list (LRU_stack).
Main changes: void StrategyAdjustStack(int buf_id, bool delete):
If (delete): delete the buffer with buf_id fromt the LRU_stack, granted that buffer buf_id exists in the stack.
If (!delete): adjust the position of the buffer buf_id, move it to the head of the stack.