oracle执行计划

SQL> set autot trace

SQL> select count(*) from dba_objects;

Execution Plan
----------------------------------------------------------
Plan hash value: 2598313856

-----------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 30 (4)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 | | | |
| 2 | VIEW | DBA_OBJECTS | 8882 | | 30 (4)| 00:00:01 |
| 3 | UNION-ALL | | | | | |
|* 4 | FILTER | | | | | |
|* 5 | HASH JOIN | | 10018 | 743K| 29 (4)| 00:00:01 |
| 6 | TABLE ACCESS FULL | USER$ | 28 | 84 | 2 (0)| 00:00:01 |
|* 7 | TABLE ACCESS FULL | OBJ$ | 10018 | 714K| 26 (0)| 00:00:01 |
|* 8 | TABLE ACCESS BY INDEX ROWID| IND$ | 1 | 7 | 2 (0)| 00:00:01 |
|* 9 | INDEX UNIQUE SCAN | I_IND1 | 1 | | 1 (0)| 00:00:01 |
| 10 | NESTED LOOPS | | 1 | 16 | 1 (0)| 00:00:01 |
| 11 | INDEX FULL SCAN | I_LINK1 | 1 | 13 | 0 (0)| 00:00:01 |
| 12 | TABLE ACCESS CLUSTER | USER$ | 1 | 3 | 1 (0)| 00:00:01 |
|* 13 | INDEX UNIQUE SCAN | I_USER# | 1 | | 0 (0)| 00:00:01 |
-----------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

4 - filter("O"."TYPE#"<>1 AND "O"."TYPE#"<>10 OR "O"."TYPE#"=1 AND (SELECT 1 FROM
"SYS"."IND$" "I" WHERE "I"."OBJ#"=:B1 AND ("I"."TYPE#"=1 OR "I"."TYPE#"=2 OR
"I"."TYPE#"=3 OR "I"."TYPE#"=4 OR "I"."TYPE#"=6 OR "I"."TYPE#"=7 OR "I"."TYPE#"=9))=1)
5 - access("O"."OWNER#"="U"."USER#")
7 - filter("O"."NAME"<>'_NEXT_OBJECT' AND "O"."NAME"<>'_default_auditing_options_'
AND "O"."LINKNAME" IS NULL)
8 - filter("I"."TYPE#"=1 OR "I"."TYPE#"=2 OR "I"."TYPE#"=3 OR "I"."TYPE#"=4 OR
"I"."TYPE#"=6 OR "I"."TYPE#"=7 OR "I"."TYPE#"=9)
9 - access("I"."OBJ#"=:B1)
13 - access("L"."OWNER#"="U"."USER#")

Note
-----
- dynamic sampling used for this statement --表示表没有做分析，使用了动态采样的方式来获取表数据信息

Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
2267 consistent gets
0 physical reads
0 redo size
412 bytes sent via SQL*Net to client
385 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed

执行计划顺序

6,7,5,9,8,4,11,13,12,10,3,2,1,0

Id: 是一个序列号

Operation: 是当前操作的内容

Rows: oracle估算当前操作的返回结果集

Cost (%CPU):oracle计算出来的一个数值，用于说明SQL执行的代价

Time: oracle估算当前操作的时间

access:表示这个条件的值将会影响数据的访问路径

filter: 表示条件的值并不会影响数据访问路径，只起到过滤的作用