CBO各種型別成本計算公式

CBO各種型別成本計算公式如下：

Tablescan cost= HWM/dbf_mbrc (參看“增加db_block_size能否提高I/O效能”)

Unique scan cost = blevel +1

Fast Full Scan cost=leaf_blocks/adj_mbrc

Index-only cost = Blevel + effective index selectivity * leaf_blocks

Range Cost = Blevel + effectivity index selectivity* leaf_blocks
                           + effective table selectivity * clustering_factor
(參看“B-TREE成本計算”)

nested loop join cost =outer access cost + (inner access cost * outer cardinality)

sort merge join cost = outer access cost + inner access cost + sort costs

hash join cost = (outer access cost * # of hash partitions) + inner access cost
 

來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/354732/viewspace-616169/，如需轉載，請註明出處，否則將追究法律責任。