설문조사
PostgreSQL/PPAS 관련 듣고 싶은 교육은


총 게시물 72건, 최근 0 건
   

옵티마이저 COST 값에 영향을 주는 핵심 패러미터들

글쓴이 : PostgresDBA 날짜 : 2013-06-28 (금) 23:11 조회 : 4638
Parameter  Description Default  vs page read 
 seq_page_cost  cost of sequentially fetched disk page.  1.00  
 random_page_cost  cost of nonsequentially fetched disk page.  4.00  4x slower
 cpu_tuple_cost  cost of processing each tuple (row).  0.01  100x faster
 cpu_operator_cost  cost of processing each operator or function call.  0.0025  400x faster
 cpu_index_tuple_cost  cost of processing each index entry during an index scan.  0.005  1000x faster

•Costs are estimates of the time a node is expected to take
•By default costs are in units of “time a sequential 8kb block read takes
•Each node has two costs, “startup” cost and “total” cost
•Costs cumulative – parents assume their children's costs
•Optimizer selects plans based on overall lowest startup and total cost

위 5가지 패러미터가 옵티마이저 플랜 수립에 직접적 영향을 주는 핵심 패러미터들입니다.
SQL 튜닝 전문가라면 반드시 살펴봐야할 패러미터들입니다.

   

postgresdba.com