這篇文章主要介紹數(shù)據(jù)庫中sql plan baseline怎么用，文中介紹的非常詳細，具有一定的參考價值，感興趣的小伙伴們一定要看完！
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測試內(nèi)容：
1、dba_sql_plan_baselines表中和時間有關(guān)的四個字段CREATED，LAST_MODIFIED，LAST_EXECUTED，LAST_VERIFIED的變化規(guī)律
2、候選sql plan變?yōu)閍ccepted sql plan baseline的幾種方法
3、SQL語句對應(yīng)的sql plan baseline均失效的情況下Optimizer將新生成的執(zhí)行計劃演進為sql plan baseline的過程
4、不同用戶針對各自用戶下的表，執(zhí)行同一條sql語句， sql plan baseline的共享機制
建立測試用表：
grant connect,resource,unlimited tablespace to scott identified by sdfg_1234;
create table scott.t1 tablespace ts_pub as select * from dba_objects;
create table scott.t2 tablespace ts_pub as select * from dba_objects where rownum<100;
exec dbms_stats.gather_table_stats(ownname=>'scott',tabname=>'t1',method_opt=>'for all columns size 1',cascade=>TRUE,no_invalidate=>FALSE);
exec dbms_stats.gather_table_stats(ownname=>'scott',tabname=>'t2',method_opt=>'for all columns size 1',cascade=>TRUE,no_invalidate=>FALSE);
1、dba_sql_plan_baselines表中和時間有關(guān)字段的變化規(guī)律，涉及到以下4個字段
CREATED
LAST_MODIFIED
LAST_EXECUTED
LAST_VERIFIED
###開啟session級的sql capture，自動生成首條sql plan baseline
--session 1，設(shè)置Session級的capture
SQL> select * from dba_sql_plan_baselines;
no rows selected
alter system optimizer_capture_sql_plan_baselines=TRUE;
select count(*) from scott.t1 where object_id in (select object_id from scott.t2);
--session 2，dba_sql_plan_baselines中沒有記錄，因為上述sql只執(zhí)行了一次
select sql_handle,sql_text,plan_name,creator,last_modified,last_executed,last_verified from dba_sql_plan_baselines;
--session 1，再次執(zhí)行一遍sql
select count(*) from scott.t1 where object_id in (select object_id from scott.t2);
--session 2，dba_sql_plan_baselines產(chǎn)生了首條sql plan baseline，首條初始狀態(tài)就是accepted
select sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified from dba_sql_plan_baselines;
###上述結(jié)果中的時間點字段值，last_verified值為空，因為其是這條sql生成的首條baseline所以沒有經(jīng)過驗證；因為是新建的sql plan baseline其余三個時間字段值都一樣
CREATED：02-JUL-14 02.37.20.000000 PM
LAST_MODIFIED：02-JUL-14 02.37.20.000000 PM
LAST_EXECUTED：02-JUL-14 02.37.20.000000 PM
LAST_VERIFIED：NULL
###上述結(jié)果中的時間點字段值，last_verified值為空，因為其是這條sql生成的首條baseline所以沒有經(jīng)過
--session 1，第三次執(zhí)行sql，執(zhí)行前關(guān)閉sql capture參數(shù)
alter session set optimizer_capture_sql_plan_baselines=FALSE;
select count(*) from scott.t1 where object_id in (select object_id from scott.t2);
--session 2，觀察時間字段狀態(tài)，CREATED、LAST MODIFIED兩個字段值沒有變化，這個可以理解，LAST_EXECUTED值應(yīng)該變化為最近一次的執(zhí)行時間，但事實卻沒有變化，即使alter system flush shared_pool以后重新執(zhí)行語句，也沒有變化
select sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified from dba_sql_plan_baselines;
###通過DBMS_XPLAN.DISPLAY_SQL_PLAN_BASELINE查看sql_plan_baseline對應(yīng)的執(zhí)行計劃為FTS
select * from table(dbms_xplan.display_sql_plan_baseline(sql_handle=>'SQL_d11d993788ae4828',plan_name=>'SQL_PLAN_d27ct6y4awk1822a9c5af'));
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------
SQL handle: SQL_d11d993788ae4828
SQL text: select count(*) from scott.t1 where object_id in (select object_id from
scott.t2)
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
Plan name: SQL_PLAN_d27ct6y4awk1822a9c5af Plan id: 581551535
Enabled: YES Fixed: NO Accepted: YES Origin: AUTO-CAPTURE
--------------------------------------------------------------------------------
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 1240933221
------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 9 | 462 (2)| 00:00:06 |
| 1 | SORT AGGREGATE | | 1 | 9 | | |
|* 2 | HASH JOIN RIGHT SEMI| | 3 | 27 | 462 (2)| 00:00:06 |
| 3 | TABLE ACCESS FULL | T2 | 99 | 297 | 5 (0)| 00:00:01 |
| 4 | TABLE ACCESS FULL | T1 | 177K| 1042K| 455 (1)| 00:00:06 |
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("OBJECT_ID"="OBJECT_ID")
28 rows selected.
###t1表的object_id字段上創(chuàng)建索引，再次執(zhí)行sql
create index scott.ind_objid_t1 on scott.t1(object_id) tablespace ts_pub;
exec dbms_stats.gather_table_stats(ownname=>'scott',tabname=>'t1',method_opt=>'for all columns size 1',cascade=>TRUE,no_invalidate=>FALSE);
exec dbms_stats.gather_table_stats(ownname=>'scott',tabname=>'t2',method_opt=>'for all columns size 1',cascade=>TRUE,no_invalidate=>FALSE);
###dba_sql_plan_baselines里又生成了一條plan_name= SQL_PLAN_d27ct6y4awk18b1b38b11(sql_handle與前一條相同的sql)，但沒有被accepted的baseline，這條記錄的CREATED、LAST_MODIFIED字段表明了該條baseline的創(chuàng)建時間，LAST_EXECUTED、LAST_VERIFIED均為空值
col sql_handle format a20
col creator format a5
col sql_text format a50
col created format a30
col last_modified format a30
col last_executed format a30
col last_verified format a30
set linesize 190
set pagesize 200
select sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified from dba_sql_plan_baselines;
###執(zhí)行sql，雖然有索引，但因為baseline的存在，走的依然是FTS
set autotrace traceonly;
SQL> select count(*) from scott.t1 where object_id in (select object_id from scott.t2);
Execution Plan
----------------------------------------------------------
Plan hash value: 1240933221
------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 9 | 462 (2)| 00:00:06 |
| 1 | SORT AGGREGATE | | 1 | 9 | | |
|* 2 | HASH JOIN RIGHT SEMI| | 3 | 27 | 462 (2)| 00:00:06 |
| 3 | TABLE ACCESS FULL | T2 | 99 | 297 | 5 (0)| 00:00:01 |
| 4 | TABLE ACCESS FULL | T1 | 177K| 1042K| 455 (1)| 00:00:06 |
------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("OBJECT_ID"="OBJECT_ID")
Note
-----
- SQL plan baseline "SQL_PLAN_d27ct6y4awk1822a9c5af" used for this statement
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
2557 consistent gets
2556 physical reads
0 redo size
526 bytes sent via SQL*Net to client
519 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
###人工演進sql plan baseline，根據(jù)Buffer Get優(yōu)化前后的對比2557/11=232.45，得出使用索引的sql plan baseline所獲得的性能是FTS的232倍，oracle情況下根據(jù)隱含參數(shù)_plan_verify_improvement_margin(默認值為150，表示1.5倍)的值決定性能達到原先多少倍時accept新的sql plan baseline，此例中已經(jīng)達到了232被，所以當(dāng)讓是verified and accepted
set serveroutput on
set long 10000
declare
result_clob clob;
begin
result_clob:=DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE(sql_handle=>'SQL_d11d993788ae4828',plan_name=>'SQL_PLAN_d27ct6y4awk18b1b38b11',verify=>'YES',commit=>'YES');
dbms_output.put_line(result_clob);
end;
/
-------------------------------------------------------------------------------，
Evolve SQL Plan Baseline
Report
-------------------------------------------------------------------------
------
Inputs:
-------
SQL_HANDLE = SQL_d11d993788ae4828
PLAN_NAME =
SQL_PLAN_d27ct6y4awk18b1b38b11
TIME_LIMIT = DBMS_SPM.AUTO_LIMIT
VERIFY =
YES
COMMIT = YES
Plan:
SQL_PLAN_d27ct6y4awk18b1b38b11
------------------------------------
Plan was
verified: Time used .901 seconds.
Plan passed performance criterion: 232.77
times better than baseline plan.
Plan was changed to an accepted plan.
Baseline Plan Test Plan Stats Ratio
------------- --------- -----------
Execution Status:
COMPLETE COMPLETE
Rows Processed: 1
1
Elapsed Time(ms): 59.641 .298 200.14
CPU Time(ms): 34.444 0
Buffer Gets:
2557 11 232.45
Physical Read Requests: 0
0
Physical Write Requests: 0 0
Physical Read
Bytes: 0 0
Physical Write Bytes:
0 0
Executions: 1
1
-----------------------------------------------------------------------------
--
Report
Summary
------------------------------------------------------------------------
-------
Number of plans verified: 1
Number of plans accepted: 1
PL/SQL procedure successfully completed.
###查看PLAN_NAME=SQL_PLAN_d27ct6y4awk18b1b38b11對應(yīng)sql plan baseline，LAST_VERIFIED和
LAST_MODIFIED為同一個時間，LAST_VERIFIED表示在這個時間完成了Verify動作，LAST_MODIFIED表示在
Verify通過后將此baseline從not accepted變?yōu)閍ccepted的時間。
CREATED: 02-JUL-14 03.22.41.000000 PM
LAST_MODIFIED: 02-JUL-14 03.44.10.000000 PM
LAST_VERIFIED:02-JUL-14 03.44.10.000000 PM
###執(zhí)行該SQL后發(fā)現(xiàn)last_executed時間已經(jīng)是最新的時間了
SQL> select count(*) from scott.t1 where object_id in (select object_id from scott.t2);
select sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified from dba_sql_plan_baselines;
LAST_EXECUTED:02-JUL-14 04.25.33.000000 PM
###用dbms_xplan.display_sql_plan_baseline顯示Plan_name=SQL_PLAN_d27ct6y4awk18b1b38b11的執(zhí)行計劃，這次采用的是Nest Loop
SQL> select * from table(dbms_xplan.display_sql_plan_baseline(sql_handle=>'SQL_d11d993788ae4828',plan_name=>'SQL_PLAN_d27ct6y4awk18b1b38b11'));
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
SQL handle: SQL_d11d993788ae4828
SQL text: select count(*) from scott.t1 where object_id in (select object_id fro
m
scott.t2)
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
Plan name: SQL_PLAN_d27ct6y4awk18b1b38b11 Plan id: 2981333777
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Enabled: YES Fixed: NO Accepted: YES Origin: AUTO-CAPTURE
--------------------------------------------------------------------------------
Plan hash value: 2406492491
--------------------------------------------------------------------------------
-----
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
|
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
-----
| 0 | SELECT STATEMENT | | 1 | 9 | 56 (2)| 00:00
:01 |
| 1 | SORT AGGREGATE | | 1 | 9 | |
|
| 2 | NESTED LOOPS | | 99 | 891 | 56 (2)| 00:00
:01 |
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
| 3 | SORT UNIQUE | | 99 | 297 | 5 (0)| 00:00
:01 |
| 4 | TABLE ACCESS FULL| T2 | 99 | 297 | 5 (0)| 00:00
:01 |
|* 5 | INDEX RANGE SCAN | IND_OBJID_T1 | 1 | 6 | 1 (0)| 00:00
:01 |
--------------------------------------------------------------------------------
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
-----
Predicate Information (identified by operation id):
---------------------------------------------------
5 - access("OBJECT_ID"="OBJECT_ID")
階段總結(jié)：
CREATED：sql plan生成到plan_history的時間(可以是accept或者not accept狀態(tài))
LAST_MODIFIED：sql plan上一次修改的時間，這個修改時間反映了sql plan演進過程中將not
accetped的sql plan更新為accepted動作發(fā)生的時間，也能反映使用alter_sql_plan_baseline
對于sql plan任何屬性更改的時間
LAST_VERIFIED：sql plan最后一次被驗證的時間，同一個plan被驗證一遍之后如果再重復(fù)進
行驗證，時間還是停留在首次驗證的時間；第一條sql plan自動成為sql plan baseline時其
last_verified時間為空，說明其沒有經(jīng)過verify，即使后續(xù)對首條sql plan人工進行演進，其last_verified時間依然為空
LAST_EXECUTED：名義上為最后一次執(zhí)行的時間，實際測下來定格在首次執(zhí)行的時間，后續(xù)
的執(zhí)行并不會更新
2、使sql plan變?yōu)閍ccepted sql plan baseline的幾種方法
(1) 調(diào)用Dbms_spm.evolve_sql_plan_baseline函數(shù)，需要人工調(diào)用(在12c版本里已經(jīng)引入sql plan evolve advisor能實現(xiàn)自動演進sql plan baseline)，這個是最常用的方法，只做如下說明：
其中Verify=yes表示經(jīng)過optimizer驗證
verify=no表示不經(jīng)過optimizer驗證強制變?yōu)閍ccepted狀態(tài)
(2) 調(diào)用Dbms_spm.LOAD_PLANS_FROM_CURSOR_CACHE或者LOAD_PLANS_FROM_SQLSET函數(shù)，這里使用LOAD_PLANS_FROM_CURSOR_CACHE函數(shù)將shared pool中已經(jīng)存在的執(zhí)行計劃load到baseline，且狀態(tài)變?yōu)閍ccepted；
###執(zhí)行sql，使其cache到shared pool
variable v_objid number;
exec :v_objid:=1000;
select count(*) from scott.t1 where object_id<:v_objid;
SQL> select sql_text,sql_id,child_number,plan_hash_value from v$sql where sql_text like 'select count(*) from scott.t1%';
SQL_TEXT SQL_ID CHILD_NUMBER PLAN_HASH_VALUE
------------------------------------------------------------------------------------------ ------------- ------------ ---------------
select count(*) from scott.t1 where object_id<:v_objid 9hup7n51za19u 0 4020739011
###顯示執(zhí)行計劃
select * from table(dbms_xplan.display_cursor(sql_id=>'9hup7n51za19u',cursor_child_no=>0,format=>'ALL'));
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
SQL_ID 9hup7n51za19u, child number 0
-------------------------------------
select count(*) from scott.t1 where object_id<:v_objid
Plan hash value: 4020739011
--------------------------------------------------------------------------------
--
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
|
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
--
| 0 | SELECT STATEMENT | | | | 5 (100)|
|
| 1 | SORT AGGREGATE | | 1 | 6 | |
|
|* 2 | INDEX RANGE SCAN| IND_OBJID_T1 | 8893 | 53358 | 5 (0)| 00:00:01
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
|
--------------------------------------------------------------------------------
--
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
1 - SEL$1
2 - SEL$1 / T1@SEL$1
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("OBJECT_ID"<:V_OBJID)
Column Projection Information (identified by operation id):
-----------------------------------------------------------
1 - (#keys=0) COUNT(*)[22]
###從shared pool中將上述sql的執(zhí)行計劃load到sql plan baseline，load進來之后就變成了Accepted，沒有verify的過程
set serveroutput on
declare
result_int pls_integer;
begin
result_int:=DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE(sql_id=>'9hup7n51za19u',plan_hash_value=>4020739011,fixed=>'NO',enabled=>'YES');
dbms_output.put_line(result_int);
end;
/
###在dba_sql_plan_baselines中找到了該條sql plan baseline，已經(jīng)被accepted
select sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified from dba_sql_plan_baselines where sql_text like '%v_objid';
###再次執(zhí)行sql時已經(jīng)能用到了這條sql plan baseline了
variable v_objid number;
exec :v_objid:=500;
select count(*) from scott.t1 where object_id<:v_objid;
set autotrace traceonly;
select count(*) from scott.t1 where object_id<:v_objid;
Execution Plan
----------------------------------------------------------
Plan hash value: 4020739011
--------------------------------------------------------------------------------
--
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
|
--------------------------------------------------------------------------------
--
| 0 | SELECT STATEMENT | | 1 | 6 | 5 (0)| 00:00:01
|
| 1 | SORT AGGREGATE | | 1 | 6 | |
|
|* 2 | INDEX RANGE SCAN| IND_OBJID_T1 | 8893 | 53358 | 5 (0)| 00:00:01
|
--------------------------------------------------------------------------------
--
Predicate Information (identified by operation id):
---------------------------------------------------
2 -
access("OBJECT_ID" Note ----- - SQL plan baseline
"SQL_PLAN_gm8nknf6mhghn28a6f5d9" used for this statement Statistics ---------------------------------------------------------- 27
recursive calls 16
db block gets 15
consistent gets 13
physical reads 3136
redo size 527
bytes sent via SQL*Net to client 520
bytes received via SQL*Net from client 2
SQL*Net roundtrips to/from client 0
sorts (memory) 0
sorts (disk) 1
rows processed (3) 通過dbms_sqltune對SQL語句進行調(diào)優(yōu)，并接受其調(diào)優(yōu)建議 這里沿用本文第一部分對于select count(*) from scott.t1 where object_id in (select object_id
from scott.t2)語句生成的兩條sql plan baseline，作如下處理：刪除走索引的那條plan（只保留FTS）->使用sql tuning advisor對語句進行調(diào)優(yōu)->接受advisor使用索引訪問的建議 ###人工刪除掉走索引的sql
plan set
numformat 9999999999999999999999999 col
sql_handle format a20 col
creator format a5 col
sql_text format a50 col
created format a30 col
last_modified format a30 col
last_executed format a30 col
last_verified format a30 set
linesize 180 select sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified
from dba_sql_plan_baselines where sql_handle='SQL_d11d993788ae4828'; --刪除其中使用索引的那條 set
serveroutput on declare result_int
pls_integer; begin result_int:=dbms_spm.drop_sql_plan_baseline(sql_handle=>'SQL_d11d993788ae4828',plan_name=>'SQL_PLAN_d27ct6y4awk18b1b38b11'); dbms_output.put_line(result_int); end; / --刪除成功只剩一條FTS的plan select
sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified
from dba_sql_plan_baselines where sql_handle='SQL_d11d993788ae4828'; ###執(zhí)行dbms_sqltune，生成并接受優(yōu)化建議 --生成tuning任務(wù) declare my_task_name
varchar2(30); my_sqltext clob; begin my_sqltext:='select
count(*) from scott.t1 where object_id in (select object_id from scott.t2)'; my_task_name:=dbms_sqltune.create_tuning_task(sql_text=>my_sqltext,user_name=>'SCOTT',scope=>'COMPREHENSIVE',time_limit=>60,task_name=>'scott_sql_tune_1',description=>'tune
1'); end; / --執(zhí)行tuning任務(wù) begin dbms_sqltune.execute_tuning_task(task_name=>'scott_sql_tune_1'); end; / ###查看sqltune報告，截取了相關(guān)內(nèi)容 set
long 9000 set
longchunksize 1000 set
linesize 800 select
dbms_sqltune.report_tuning_task('scott_sql_tune_1') from dual; 1- Original With Adjusted Cost ------------------------------ Plan hash value: 1240933221 DBMS_SQLTUNE.REPORT_TUNING_TASK('SCOTT_SQL_TUNE_1') -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ------------------------------------------------------------------------------ | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ------------------------------------------------------------------------------ | 0 | SELECT STATEMENT |
| 1 | 9 |
462 (2)| 00:00:06 | | 1 | SORT AGGREGATE |
| 1 | 9 | | | |* 2 | HASH JOIN RIGHT SEMI| |
3 | 27 | 462
(2)| 00:00:06 | | 3 | TABLE ACCESS FULL | T2
| 99 | 297 |
5 (0)| 00:00:01 | | 4 | TABLE ACCESS FULL | T1
| 177K| 1042K|
455 (1)| 00:00:06 | ------------------------------------------------------------------------------ Predicate Information (identified by operation id): DBMS_SQLTUNE.REPORT_TUNING_TASK('SCOTT_SQL_TUNE_1') 2- Using SQL Profile -------------------- Plan hash value: 2406492491 ------------------------------------------------------------------------------------- | Id | Operation | Name | Rows
| Bytes | Cost (%CPU)| Time | ------------------------------------------------------------------------------------- DBMS_SQLTUNE.REPORT_TUNING_TASK('SCOTT_SQL_TUNE_1') -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 |
9 | 56 (2)| 00:00:01 | | 1 | SORT AGGREGATE | | 1 |
9 | | | | 2 | NESTED LOOPS | | 99 |
891 | 56 (2)| 00:00:01 | | 3 | SORT UNIQUE | | 99 |
297 | 5 (0)| 00:00:01 | | 4 | TABLE ACCESS FULL| T2 |
99 | 297 | 5
(0)| 00:00:01 | |* 5 | INDEX RANGE SCAN | IND_OBJID_T1 | 1 |
6 | 1 (0)| 00:00:01 | ------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- ###接受Advisor推薦走索引的Profile，同時可以看到dba_sql_plan_baseline里又增加了一條accepted=yes的plan，這條正是我們剛才刪除的，表明接受dbms_sqltune的調(diào)優(yōu)結(jié)果也可以實現(xiàn)sql plan baseline的演進 execute dbms_sqltune.accept_sql_profile(task_name=>'scott_sql_tune_1',task_owner=>'SCOTT',replace=>TRUE); select
sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified
from dba_sql_plan_baselines where sql_handle='SQL_d11d993788ae4828'; ###驗證已經(jīng)新的sql
plan baseline已經(jīng)被使用 SQL>
set autotrace traceonly explain SQL>select
count(*) from scott.t1 where object_id in (select object_id from scott.t2); Execution Plan ---------------------------------------------------------- Plan hash
value: 2406492491 ------------------------------------------------------------------------------------- | Id | Operation | Name | Rows
| Bytes | Cost (%CPU)| Time | ------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 |
9 | 56 (2)| 00:00:01 | | 1 |
SORT AGGREGATE | | 1 |
9 | | | | 2 |
NESTED LOOPS | | 99 |
891 | 56 (2)| 00:00:01 | | 3 |
SORT UNIQUE | | 99 |
297 | 5
(0)| 00:00:01 | | 4 |
TABLE ACCESS FULL| T2
| 99 | 297 |
5 (0)| 00:00:01 | |* 5 |
INDEX RANGE SCAN | IND_OBJID_T1
| 1 | 6 |
1 (0)| 00:00:01 | ------------------------------------------------------------------------------------- Predicate
Information (identified by operation id): --------------------------------------------------- 5 -
access("OBJECT_ID"="OBJECT_ID") Note ----- - SQL profile
"SYS_SQLPROF_0146fae6b2110000" used for this statement - SQL plan baseline
"SQL_PLAN_d27ct6y4awk18b1b38b11" used for this statement 階段總結(jié)： 方法(1)適用于已經(jīng)存在于sql plan history里但還未被accepted的sql plan，可以通過optimizer驗證(verify=yes)后實現(xiàn)演進，或者不通過驗證(verify=no)而直接演進為sql plan baseline 方法(2)在不開啟session級或system級自動捕捉(optimizer_capture_sql_plan_baselines=FALSE)的情況下，人工將已經(jīng)生成的執(zhí)行計劃裝載為sql plan baseline，即繞過optimizer的評估，直接演進為accepted plan的情況。這種方法需要人工確認該執(zhí)行計劃是一定是最優(yōu)的，否則會導(dǎo)致后續(xù)按照該baseline執(zhí)行的SQL產(chǎn)生性能問題 方法(3)語句出現(xiàn)性能問題后，求助sql tuning advisor得到并應(yīng)用優(yōu)化建議，生成accepted的sql plan baseline，屬于事后調(diào)優(yōu)的范疇 3、SQL語句對應(yīng)的sql plan baseline均失效的情況下，sql
plan演進會跳過verify步驟，直接變?yōu)閍ccepted ###Drop掉原有的sql plan
baseline declare result_int
pls_integer; begin result_int:=dbms_spm.drop_sql_plan_baseline(sql_handle=>'SQL_d11d993788ae4828'); end; / ###重新構(gòu)建測試環(huán)境 create
table scott.t1 tablespace ts_pub as select * from dba_objects; create
table scott.t2 tablespace ts_pub as select * from dba_objects where
rownum<100; create
index scott.ind_objid_t1 on scott.t1(object_id) tablespace ts_pub; exec dbms_stats.gather_table_stats(ownname=>'scott',tabname=>'t1',method_opt=>'for
all columns size 1',cascade=>TRUE,no_invalidate=>FALSE); exec
dbms_stats.gather_table_stats(ownname=>'scott',tabname=>'t2',method_opt=>'for
all columns size 1',cascade=>TRUE,no_invalidate=>FALSE); alter session set optimizer_capture_sql_plan_baselines=TRUE; select count(*) from scott.t1 where object_id in (select
object_id from scott.t2); --執(zhí)行至少兩次 alter session set optimizer_capture_sql_plan_baselines=FALSE; ###drop掉索引，再次執(zhí)行sql，觀察到dba_sql_plan_baselines里，索引對應(yīng)的plan REPRODUCED變成了NO，受索引被drop的影響此條plan baseline失效了；同時新增了一條FTS的plan，但狀態(tài)為not accepted drop
index scott.ind_objid_t1; select count(*) from scott.t1 where object_id in (select
object_id from scott.t2); select sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified,REPRODUCED
from dba_sql_plan_baselines where sql_handle='SQL_d11d993788ae4828'; ###現(xiàn)在把FTS的plan演進為Accepted sql plan baseline，從EVOLVE_SQL_PLAN_BASELINE函數(shù)的輸出可以看出，雖然指定了verify=YES，但因走索引的plan已經(jīng)失效，oracle并沒有進行verify就直接accept此plan了。 set
serveroutput on set long
10000 declare result_clob
clob; begin result_clob:=DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE(sql_handle=>'SQL_d11d993788ae4828',plan_name=>'SQL_PLAN_d27ct6y4awk1822a9c5af',verify=>'YES',commit=>'YES'); dbms_output.put_line(result_clob); end; / ------------------------------------------------------------------------------- Evolve SQL Plan
Baseline Report ------------------------------------------------------------------------- ------ Inputs: ------- SQL_HANDLE = SQL_d11d993788ae4828 PLAN_NAME
= SQL_PLAN_d27ct6y4awk1822a9c5af TIME_LIMIT = DBMS_SPM.AUTO_LIMIT VERIFY
= YES COMMIT
= YES Plan: SQL_PLAN_d27ct6y4awk1822a9c5af ------------------------------------ Plan was not verified. Using cost-based plan
as could not reproduce any accepted and enabled baseline plan. Plan was changed to
an accepted plan. ------------------------------------------------------------------------- ------ Report Summary ------------------------------------------------------------------------ ------- Number of plans verified: 0 Number of plans accepted: 1 ###演進的結(jié)果驗證，F(xiàn)TS 對應(yīng)的sql plan
baseline已經(jīng)變成Accepted=yes了 select sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified,REPRODUCED
from dba_sql_plan_baselines where sql_handle='SQL_d11d993788ae4828' ###對于走索引的這條sql plan baseline，若要使其重新生效，即reproduced從NO變?yōu)閅ES，必須重新建立索引并且執(zhí)行一次sql才行 select count(*) from scott.t1 where object_id in (select
object_id from scott.t2); create index scott.ind_objid_t1 on scott.t1(object_id) tablespace
ts_pub; exec
dbms_stats.gather_table_stats(ownname=>'scott',tabname=>'t1',method_opt=>'for
all columns size 1',cascade=>TRUE,no_invalidate=>FALSE); exec
dbms_stats.gather_table_stats(ownname=>'scott',tabname=>'t2',method_opt=>'for
all columns size 1',cascade=>TRUE,no_invalidate=>FALSE);
###僅通過Verify并不能使其重新生效，提示已經(jīng)是accepted sql plan baseline set serveroutput
on set long
10000 declare result_clob
clob; begin result_clob:=DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE(sql_handle=>'SQL_d11d993788ae4828',plan_name=>'SQL_PLAN_d27ct6y4awk18b1b38b11',verify=>'YES',commit=>'YES'); dbms_output.put_line(result_clob); end; / ------------------------------------------------------------------------------- Evolve SQL Plan
Baseline Report ------------------------------------------------------------------------- ------ Inputs: ------- SQL_HANDLE = SQL_d11d993788ae4828 PLAN_NAME
= SQL_PLAN_d27ct6y4awk18b1b38b11 TIME_LIMIT = DBMS_SPM.AUTO_LIMIT VERIFY
= YES COMMIT
= YES Plan: SQL_PLAN_d27ct6y4awk18b1b38b11 ------------------------------------ It is already an accepted plan. ------------------------------------------------------------------------- ------ Report Summary ------------------------------------------------------------------------ ------- There
were no SQL plan baselines that required processing. select
sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified,REPRODUCED
from dba_sql_plan_baselines where sql_handle='SQL_d11d993788ae4828' ###只有重新執(zhí)行sql，reproduced才會變?yōu)閅ES，此外還可以觀察到這兩條有效的sql plan baseline的last_verified字段均為空，表明這兩條sql plan入駐的時候都沒有經(jīng)過verify，也間接說明了入駐的當(dāng)時沒有有效的sql plan baseline存在，是被直接”保送”進了sql plan baseline select count(*) from scott.t1 where object_id
in (select object_id from scott.t2); select sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified,REPRODUCED
from dba_sql_plan_baselines where sql_handle='SQL_d11d993788ae4828'; 1、不同用戶針對各自用戶下的表，執(zhí)行同一條sql語句， sql plan
baseline的共享機制 測試場景描述：兩個用戶scott1、scott2下各有一張名為t1的表，scott1.t1(object_id)上建立名為ind_objid_t的non-unique索引，且在scott1用戶下執(zhí)行select *
from t1 where object_id<100000生成首條sql plan baseline；之后分別在以下幾種場景下使用Scott2用戶執(zhí)行同樣的語句：select * from t1 where object_id<100000，觀察是否能用到scott1用戶生成的首條sql
plan baseline，這幾種場景包括： (1) Scott2.t1(object_id)字段沒有索引 (2) Scott2.t1(object_id)字段創(chuàng)建non-unique索引，索引名稱和Scott1保持一致 (3) Scott2.t1(object_id)字段創(chuàng)建non-unique索引， 索引名稱和Scott1保持一致，人工增大clustering_factor，使Optimizer偏向選擇FTS (4) Scott2.t1(object_id)字段創(chuàng)建non-unique索引，索引名稱有別于Scott1 (5) Scott2.t1(object_id)字段創(chuàng)建unique索引，索引名稱和Scott1保持一致 (6) 重建Scott2.t1表，同時更改scott2.t1表結(jié)構(gòu)，除了object_id字段外，其余字段均和Scott2.t1中的字段不相同 數(shù)據(jù)環(huán)境準備： ###生成scott1用戶下的表 grant
connect,resource,unlimited tablespace to scott1 identified by scott1_1234; grant
plustrace to scott1; create
table scott1.t1 tablespace ts_pub as select * from dba_objects; create
index scott1.ind_objid_t on scott1.t1(object_id) tablespace ts_pub; exec
dbms_stats.gather_table_stats(ownname=>'scott1',tabname=>'t1',method_opt=>'for
all columns size 1',cascade=>TRUE,no_invalidate=>FALSE); ###生成scott2用戶下的表 grant
connect,resource,unlimited tablespace to scott2 identified by scott2_5678; grant
plustrace to scott2; create
table scott2.t1 tablespace ts_pub as select * from dba_objects; exec dbms_stats.gather_table_stats(ownname=>'scott2',tabname=>'t1',method_opt=>'for
all columns size 1',cascade=>TRUE,no_invalidate=>FALSE); ##清理現(xiàn)有環(huán)境中的sql plan baseline，保持dba_sql_plan_baseline為空 set
serveroutput on declare result_int
pls_integer; cursor
t_cur is select distinct sql_handle from dba_sql_plan_baselines; begin for v_cur
in t_cur loop result_int:=dbms_spm.drop_sql_plan_baseline(sql_handle=>v_cur.sql_handle); dbms_output.put_line(result_int); end loop; end; / alter system flush shared_pool; ##scott1用戶生成首條sql plan baseline， sqlplus scott1/scott1_1234 alter session set optimizer_capture_sql_plan_baselines=true; select * from t1 where object_id<100000; --執(zhí)行至少兩遍 alter session set optimizer_capture_sql_plan_baselines=false; select sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified,REPRODUCED
from dba_sql_plan_baselines; select * from
table(dbms_xplan.display_sql_plan_baseline(sql_handle=>'SQL_91e3f036b4b3ac44',plan_name=>'SQL_PLAN_93szh7uub7b2453067583')); --對應(yīng)的執(zhí)行計劃是index
range scan PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | |
3560 | 337K| 213
(0)| 00:00:03 | | 1
| TABLE ACCESS BY INDEX ROWID| T1 |
3560 | 337K| 213
(0)| 00:00:03 | |* 2 |
INDEX RANGE SCAN |
IND_OBJID_T | 3560 | |
10 (0)| 00:00:01 | 場景(1):Scott2.t1(object_id)字段沒有索引，Scott2用戶執(zhí)行select * from t1 where object_id<100000; select
* from t1 where object_id<100000; ###t1.object_id字段沒有索引，無法用上Scott1用戶下的baseline，但會把Scott1用戶創(chuàng)建的plan變成reproduced=NO同時在sql plan
history里生成了一條FTS的plan，Creator為scott2，狀態(tài)為not accepted select sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified,REPRODUCED
from dba_sql_plan_baselines; select *
from
table(dbms_xplan.display_sql_plan_baseline(sql_handle=>'SQL_91e3f036b4b3ac44',plan_name=>'SQL_PLAN_93szh7uub7b24dbd90e8e')); --plan_name= SQL_PLAN_93szh7uub7b24dbd90e8e執(zhí)行計劃如下 -------------------------------------------------------------------------------- SQL handle:
SQL_91e3f036b4b3ac44 SQL text:
select * from t1 where object_id<100000 -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Plan name:
SQL_PLAN_93szh7uub7b24dbd90e8e
Plan id: 3688435342 Enabled:
YES Fixed: NO Accepted: NO Origin: AUTO-CAPTURE -------------------------------------------------------------------------------- PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------- Plan hash
value: 838529891 -------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | -------------------------------------------------------------------------- | 0 | SELECT STATEMENT |
| 3560 | 337K|
456 (1)| 00:00:06 | |* 1 |
TABLE ACCESS FULL| T1 | 3560 |
337K| 456 (1)| 00:00:06 | -------------------------------------------------------------------------- 階段結(jié)論：scott2用戶的t1表上沒有索引，優(yōu)化器為sql生成的執(zhí)行計劃無法與scott1用戶創(chuàng)建的sql plan baseline匹配，所以只能采用FTS的訪問路徑添加到sql plan history，同時將scott1用戶plan_name=SQL_PLAN_93szh7uub7b2453067583置為reproduced=NO?？梢妰?yōu)化器在匹配sql plan baseline時依據(jù)的是sql_handle，和這個plan的creator無關(guān)。 場景(2):Scott2.t1(object_id)字段創(chuàng)建non-unique索引，索引名稱和Scott1保持一致 ##接著場景(1)，在scott2.t1(object_id)創(chuàng)建和scott1同名的索引 create
index scott2.ind_objid_t on scott2.t1(object_id) tablespace ts_pub; exec
dbms_stats.gather_table_stats(ownname=>'scott2',tabname=>'t1',method_opt=>'for
all columns size 1',cascade=>TRUE,no_invalidate=>FALSE); ##scott2執(zhí)行sql，看到plan_name=SQL_PLAN_93szh7uub7b2453067583重新變?yōu)镽EPRODUCED=YES了，而且通過sql語句的執(zhí)行計劃可以看到plan_name=SQL_PLAN_93szh7uub7b2453067583重新被使用上了 set
autotrace traceonly select *
from t1 where object_id<100000; | Id | Operation | Name | Rows
| Bytes | Cost (%CPU)| Time
| -------------------------------------------------------------------------------- ----------- | 0 | SELECT STATEMENT | |
3560 | 337K| 213
(0)| 00:00:03 | | 1 |
TABLE ACCESS BY INDEX ROWID| T1
| 3560 | 337K|
213 (0)| 00:00:03 | |* 2 |
INDEX RANGE SCAN |
IND_OBJID_T | 3560 | |
10 (0)| 00:00:01 | -------------------------------------------------------------------------------- ----------- Predicate
Information (identified by operation id): --------------------------------------------------- 2 - access("OBJECT_ID"<100000) Note ----- - SQL plan baseline "SQL_PLAN_93szh7uub7b2453067583" used for this
statement select sql_handle,sql_text,plan_name,enabled,accepted,creator,created,last_modified,last_executed,last_verified,REPRODUCED
from dba_sql_plan_baselines 階段結(jié)論：scott2. t1表與scott2.t1完全相同，這個相同包括表結(jié)構(gòu)、索引名稱、統(tǒng)計信息等都和scott1.t1保持一致，所以生成的執(zhí)行計劃能完全匹配scott1走索引的plan_name，REPRODUCED重新置為YES 場景(3): Scott2.t1(object_id)字段創(chuàng)建non-unique索引， 索引名稱和Scott1保持一致，人工增大clustering_factor，使Optimizer偏向選擇FTS ##創(chuàng)建Scott2.t1(object_id)索引 。。。步驟同上，此處省略 ##先把optimizer_use_sql_plan_baselines設(shè)成false，觀察一下未啟用sql
plan baseline的情況下，改大scott2.t1 表索引的clustering_factor值，對執(zhí)行計劃的影響 ---修改前走的是index
range scan alter
session set optimizer_use_sql_plan_baselines=FALSE; select
table_name,index_name,clustering_factor from user_indexes where
table_name='T1'; TABLE_NAME INDEX_NAME CLUSTERING_FACTOR ------------------------------
------------------------------ -----------------
本文題目：數(shù)據(jù)庫中sqlplanbaseline怎么用
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