oracle中查看执行计划的常用方法

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本文介绍了oracle中查看执行计划常用的方法。
1、EXPLAIN PLAN命令
2、AUTOTRACE开关
3、DBMS_XPLAN
4、10046事件

1、EXPLAIN PLAN命令
SQL> var a number;
SQL> var b number;
SQL> exec :a :=0;

PL/SQL procedure successfully completed.

SQL> exec :b :=70000;

PL/SQL procedure successfully completed.
SQL> explain plan for select count(*) fr免费云主机域名om t where object_id between :a and :b;

Explained.

SQL> select * from table(dbms_xplan.display);

PLAN_TABLE_OUTPUT
——————————————————————————–
Plan hash value: 2213771543

—————————————————————————-
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
—————————————————————————-
| 0 | SELECT STATEMENT | | 1 | 5 | 2 (0)| 00:00:01 |
| 1 | SORT AGGREGATE | | 1 | 5 | | |
|* 2 | FILTER | | | | | |
|* 3 | INDEX RANGE SCAN| T_IDX | 180 | 900 | 2 (0)| 00:00:01 |
—————————————————————————-
。。。。省略部分 SQL> set autot traceonly
SQL> select count(*) from t where object_id between :a and :b;
Execution Plan
———————————————————-
Plan hash value: 2213771543

COUNT(*)
———-
136544

SQL> select * from table(dbms_xplan.display_cursor(null,null,’advanced’));

PLAN_TABLE_OUTPUT
——————————————————————————–
SQL_ID 9cgwqzzvtw8wc, child number 0
————————————-
select count(*) from t where object_id between :a and :b

Plan hash value: 853742775

——————————————————————————–
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
——————————————————————————–
| 0 | SELECT STATEMENT | | | | 45 (100)| |
| 1 | SORT AGGREGATE | | 1 | 5 | | |

PLAN_TABLE_OUTPUT
——————————————————————————–
|* 2 | FILTER | | | | | |
|* 3 | INDEX FAST FULL SCAN| T_IDX | 50561 | 246K| 45 (0)| 00:00:01 |。。。省略部分
==》真实的执行计划应该是INDEXFAST FULL SCAN
3、DBMS_XPLAN
DBMS_XPLANB包的常用子程序为：
DISPLAY：配合explain plan for 使用
DISPLAY_CURSOR：适用于sqlplus刚刚执行过的sql执行计划，或在存储在shared pool中的执行计划。
DISPLAY_AWR：sql的执行计划从shared pool中aga out后，如果执行计划被采集到awr报告中，那么就可以使用该方法查看执行计划。
示例：SQL> select status from t where owner=user;
VALID
VALID
VALID
。。。省略部分

31206 rows selected.

SQL> select * from table(dbms_xplan.display_cursor(null,null,’advanced’));

PLAN_TABLE_OUTPUT
—————————————————————————————–
SQL_ID 7m7b6un3xtss3, child number 0
————————————-
select status from t where owner=user

Plan hash value: 47527108

——————————————————————————————
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
——————————————————————————————
| 0 | SELECT STATEMENT | | | | 13 (100)| |
| 1 | TABLE ACCESS BY INDEX ROWID| T | 2255 | 27060 | 13 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | DESC_T_INX | 70 | | 10 (0)| 00:00:01 |
——————————————————————————————

Query Block Name / Object Alias (identified by operation id):
————————————————————-

1 – SEL$1 / T@SEL$1
2 – SEL$1 / T@SEL$1

Outline Data
————-

/*+
BEGIN_OUTLINE_DATA
IGNORE_OPTIM_EMBEDDED_HINTS
OPTIMIZER_FEATURES_ENABLE(‘11.2.0.1’)
DB_VERSION(‘11.2.0.1’)
ALL_ROWS
OUTLINE_LEAF(@”SEL$1″)
INDEX_RS_ASC(@”SEL$1″ “T”@”SEL$1” “DESC_T_INX”)
END_OUTLINE_DATA
*/

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

2 – access(“T”.”SYS_NC00016$”=SYS_OP_DESCEND(USER@!))
filter(SYS_OP_UNDESCEND(“T”.”SYS_NC00016$”)=USER@!)

Column Projection Information (identified by operation id):
———————————————————–

1 – “STATUS”[VARCHAR2,7]
2 – “T”.ROWID[ROWID,10], “T”.”SYS_NC00016$”[RAW,46]

46 rows selected.
==>1.相比AUTOTRACE开关来说看不到相关的统计信息，而且要等到语句执行完成。但获得的执行计划是真实的
2.这里format参数为advanced,相比较于参数all,多了Outline Data这部分的信息输出
3.这里的Rows列值为估计值，要想看到真实值可以将format参数设置为’ALLSTATS LAST’format参数设置为’ALLSTATS LAST’示例：SQL> alter session set statistics_level =all;

Session altered.

SQL> select status from t where owner=user;
VALID
VALID
VALID
。。。。。省略部分
31206 rows selected.

SQL> select * from table(dbms_xplan.display_cursor(null,null,’allstats last’));

PLAN_TABLE_OUTPUT
————————————————————————————————————–
SQL_ID 7m7b6un3xtss3, child number 1
————————————-
select status from t where owner=user

Plan hash value: 47527108

————————————————————————————————————-
| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | Reads |
————————————————————————————————————-
| 0 | SELECT STATEMENT | | 1 | | 31206 |00:00:00.05 | 5555 | 829 |
| 1 | TABLE ACCESS BY INDEX ROWID| T | 1 | 2255 | 31206 |00:00:00.05 | 5555 | 829 |
|* 2 | INDEX RANGE SCAN | DESC_T_INX | 1 | 70 | 31206 |00:00:00.02 | 2190 | 114 |
————————————————————————————————————-

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

2 – access(“T”.”SYS_NC00016$”=SYS_OP_DESCEND(USER@!))
filter(SYS_OP_UNDESCEND(“T”.”SYS_NC00016$”)=USER@!)
==》和advanced参数相比，少了部分输出，但是能够看到每一步获取的实际记录数。
输入sqlid来查看执行计划示例：SQL> select sql_text,sql_id,version_count,executions from v$sqlarea where sql_text like ‘select status from t where owner=user’;

SQL_TEXT SQL_ID VERSION_COUNT EXECUTIONS
—————————————- ————- ————- ———-
select status from t where owner=user 7m7b6un3xtss3 2 3

SQL> select * from table(dbms_xplan.display_cursor(‘7m7b6un3xtss3′,0,’advanced’));

PLAN_TABLE_OUTPUT
——————————————————————————–
SQL_ID 7m7b6un3xtss3, child number 0
————————————-
select status from t where owner=user

Plan hash value: 47527108

Query Block Name / Object Alias (identified by operation id):
————————————————————-

1 – SEL$1 / T@SEL$1
2 – SEL$1 / T@SEL$1

Outline Data
————-

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

2 – access(“T”.”SYS_NC00016$”=SYS_OP_DESCEND(USER@!))
filter(SYS_OP_UNDESCEND(“T”.”SYS_NC00016$”)=USER@!)

Column Projection Information (identified by operation id):
———————————————————–

1 – “STATUS”[VARCHAR2,7]
2 – “T”.ROWID[ROWID,10], “T”.”SYS_NC00016$”[RAW,46]
display_awr 示例：SQL> select sql_text,sql_id,version_count,executions from v$sqlarea where sql_text like ‘select status from t where owner=user’;

no rows selected

SQL> select * from table(dbms_xplan.display_cursor(‘7m7b6un3xtss3′,0,’advanced’));

PLAN_TABLE_OUTPUT
————————————————————————-
SQL_ID: 7m7b6un3xtss3, child number: 0 cannot be found

SQL> select * from table(dbms_xplan.display_awr(‘7m7b6un3xtss3’));

PLAN_TABLE_OUTPUT
————————————————————————-
SQL_ID 7m7b6un3xtss3
——————–
select status from t where owner=user

Plan hash value: 47527108

————————————————————————–
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
————————————————————————–
| 0 | SELECT STATEMENT | | | | 13 (100)| |
| 1 | TABLE ACCESS BY INDEX ROWID| T | 2255 | 27060 | 13 (0)| 00:00:01 |
| 2 | INDEX RANGE SCAN | DESC_T_INX | 70 | | 10 (0)| 00:00:01 |

==>1、相同的执行计划也可以通过@?/rdbms/admin/awrsqrpt 命令获取。
4、10046方式SQL> alter session set tracefile_identifier=plan_10046;

Session altered.

SQL> alter session set events ‘10046 trace name context forever,level 12’;

Session altered.

SQL> select status from t where owner=user;
VALID
VALID
VALID
。。。省略部分

31206 rows selected.

SQL>
SQL> alter session set events ‘10046 trace name context off’;

Session altered.==>可以根据diagnostic_dest 参数找到plan_10046的文件。
使用tkprof进行输出：[ora11@ora12c ~]$ tkprof /ora11_10/ora11/diag/rdbms/ora11/ora11/trace/ora11_ora_26758_PLAN_10046.trc PLAN_10046.trc

TKPROF: Release 11.2.0.1.0 – Development on Tue Aug 15 21:14:49 2017

SQL ID: 57fcnar0x2buq
Plan Hash: 47527108
select status
from
t where owner=user

call count cpu elapsed disk query current rows
——- —— ——– ———- ———- ———- ———- ———-
Parse 1 0.00 0.00 11 57 0 0
Execute 1 0.00 0.00 0 0 0 0
Fetch 2082 0.13 0.13 1007 5555 0 31206
——- —— ——– ———- ———- ———- ———- ———-
total 2084 0.14 0.13 1018 5612 0 31206

Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: SYS

Rows Row Source Operation
——- —————————————————
31206 TABLE ACCESS BY INDEX ROWID T (cr=5555 pr=1007 pw=0 time=76792 us cost=13 size=27060 card=2255)
31206 INDEX RANGE SCAN DESC_T_INX (cr=2190 pr=114 pw=0 time=29158 us cost=10 size=0 card=70)(object id 99885)“oracle中查看执行计划的常用方法”的内容就介绍到这里了，感谢大家的阅读。如果想了解更多行业相关的知识可以关注百云网站，小编将为大家输出更多高质量的实用文章！

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