利用AWR查看SQL执行计划
利用AWR查看SQL执行计划
在AWR中定位到问题SQL语句后想要了解该SQL statement的具体执行计划,于是就用AWR报告中得到的SQL ID去V$SQL等几个动态性能视图中查询,但发现V$SQL或V$SQL_PLAN视图都已经找不到对应SQL ID的记录,一般来说这些语句已经从shared pool共享池中被替换出去了。
这个时候我们可以尝试使用DBMS_XPLAN.DISPLAY_AWR存储过程来将Oracle Automatic Workload Repository自动负载仓库中记录的SQL语句相关信息抽取出来,如:
SYS@ orcl> select /* extrace_awr */ count(*) from redo_test; COUNT(*) ---------- 213495 SYS@ orcl> select sql_id from v$sql where sql_text like '%extrace_awr%' and sql_text not like '%like%'; SQL_ID ------------- 7d0r6vd8yccuy SYS@ orcl> exec dbms_workload_repository.create_snapshot(); PL/SQL procedure successfully completed. SYS@ orcl> select * from table(dbms_xplan.display_cursor('7d0r6vd8yccuy',0)); PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------- SQL_ID 7d0r6vd8yccuy, child number 0 ------------------------------------- select /* extrace_awr */ count(*) from redo_test Plan hash value: 4170294667 ------------------------------------------------------------------------ | Id | Operation | Name | Rows | Cost (%CPU)| Time | ------------------------------------------------------------------------ | 0 | SELECT STATEMENT | | | 874 (100)| | | 1 | SORT AGGREGATE | | 1 | | | | 2 | TABLE ACCESS FULL| REDO_TEST | 189K| 874 (1)| 00:00:11 | ------------------------------------------------------------------------ Note ----- - dynamic sampling used for this statement (level=2) # 冲刷共享池后v$SQL/V$SQL_PLAN等动态视图内的记录会消失, # 需要注意的是如果在AWR快照自动生成之前冲刷了共享池,那么可能丢失SQL的执行统计信息 SYS@ orcl> alter system flush shared_pool; System altered. SYS@ orcl> select * from table(dbms_xplan.display_cursor('7d0r6vd8yccuy',0)); PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------- SQL_ID: 7d0r6vd8yccuy, child number: 0 cannot be found # 此时就可以利用dbms_xplan.display_awr存储过程来抓取该SQL_ID对应的执行计划 SYS@ orcl> select * from table(dbms_xplan.display_awr('7d0r6vd8yccuy')); PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------- SQL_ID 7d0r6vd8yccuy -------------------- select /* extrace_awr */ count(*) from redo_test Plan hash value: 4170294667 ------------------------------------------------------------------------ | Id | Operation | Name | Rows | Cost (%CPU)| Time | ------------------------------------------------------------------------ | 0 | SELECT STATEMENT | | | 874 (100)| | | 1 | SORT AGGREGATE | | 1 | | | | 2 | TABLE ACCESS FULL| REDO_TEST | 189K| 874 (1)| 00:00:11 | ------------------------------------------------------------------------ Note ----- - dynamic sampling used for this statement (level=2) SYS@ orcl> select * from table(dbms_xplan.display_awr('7d0r6vd8yccuy',null,null,'all')); PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------- SQL_ID 7d0r6vd8yccuy -------------------- select /* extrace_awr */ count(*) from redo_test Plan hash value: 4170294667 ------------------------------------------------------------------------ | Id | Operation | Name | Rows | Cost (%CPU)| Time | ------------------------------------------------------------------------ | 0 | SELECT STATEMENT | | | 874 (100)| | | 1 | SORT AGGREGATE | | 1 | | | | 2 | TABLE ACCESS FULL| REDO_TEST | 189K| 874 (1)| 00:00:11 | ------------------------------------------------------------------------ Query Block Name / Object Alias (identified by operation id): ------------------------------------------------------------- 1 - SEL$1 2 - SEL$1 / REDO_TEST@SEL$1 Note ----- - dynamic sampling used for this statement (level=2) # 也可以从 dba_hist_sql_plan/dba_hist_sqltext等awr历史视图中直接观察该SQL ID对应的语句 SYS@ orcl> select operation, options, object_name from dba_hist_sql_plan where sql_id='7d0r6vd8yccuy'; OPERATION OPTIONS OBJECT_NAME ------------------------------ ------------------------------ ------------------------------- SELECT STATEMENT SORT AGGREGATE TABLE ACCESS FULL REDO_TEST