Archive for December 13th, 2008
arraysize对TFS和IFFS的影响
Saturday, December 13th, 2008
今天发现一个问题，对一个索引执行index fast full scan 的时候，如果在这之前进行了排序，逻辑读会少很多：
例子：
select id from A ;
xecution Plan
———————————————————-
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=62 Card=275240 Bytes=1100960)
1 0 INDEX (FAST FULL SCAN) OF ‘PK_T’ (NON-UNIQUE) (Cost=62 Card=275240 Bytes=1100960)
Statistics
———————————————————-
0 recursive calls
0 db block gets
3326 consistent gets
0 physical reads
0 redo size
1955968 bytes sent via SQL*Net to client
30397 bytes received [...]
