【DB笔试面试610】在Oracle中,SPM的使用有哪些步骤?
作者:互联网
♣题目 部分
在Oracle中,SPM的使用有哪些步骤?
♣答案部分
取消自动捕获,也可以不取消自动捕捉:
1show parameter baselines2ALTER SYSTEM SET OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES=FALSE;show parameter baselines 2ALTER SYSTEM SET OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES=FALSE;
执行:
1[ZHLHRSPMDB2:oracle]:/oracle>ORACLE_SID=dlhr 2[ZHLHRSPMDB2:oracle]:/oracle>sqlplus / as sysdba 3 4SQL*Plus: Release 11.2.0.4.0 Production on Thu May 26 15:47:55 2016 5 6Copyright (c) 1982, 2013, Oracle. All rights reserved. 7 8 9Connected to:10Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production11With the Partitioning, Real Application Clusters, OLAP, Data Mining12and Real Application Testing options1314SYS@dlhr> conn lhr/lhr15Connected.16LHR@dlhr> 17LHR@dlhr> 18LHR@dlhr> 19LHR@dlhr> select * from v$version;2021BANNER22--------------------------------------------------------------------------------23Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production24PL/SQL Release 11.2.0.4.0 - Production25CORE 11.2.0.4.0 Production26TNS for IBM/AIX RISC System/6000: Version 11.2.0.4.0 - Production27NLSRTL Version 11.2.0.4.0 - Production2829LHR@dlhr> show parameter baselines3031NAME TYPE VALUE32------------------------------------ ----------- ------------------------------33optimizer_capture_sql_plan_baselines boolean TRUE34optimizer_use_sql_plan_baselines boolean TRUE3536LHR@dlhr> ALTER SYSTEM SET OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES=FALSE;3738System altered. 2[ZHLHRSPMDB2:oracle]:/oracle>sqlplus / as sysdba 3 4SQL*Plus: Release 11.2.0.4.0 Production on Thu May 26 15:47:55 2016 5 6Copyright (c) 1982, 2013, Oracle. All rights reserved. 7 8 9Connected to: 10Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production 11With the Partitioning, Real Application Clusters, OLAP, Data Mining 12and Real Application Testing options 13 14SYS@dlhr> conn lhr/lhr 15Connected. 16LHR@dlhr> 17LHR@dlhr> 18LHR@dlhr> 19LHR@dlhr> select * from v$version; 20 21BANNER 22-------------------------------------------------------------------------------- 23Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production 24PL/SQL Release 11.2.0.4.0 - Production 25CORE 11.2.0.4.0 Production 26TNS for IBM/AIX RISC System/6000: Version 11.2.0.4.0 - Production 27NLSRTL Version 11.2.0.4.0 - Production 28 29LHR@dlhr> show parameter baselines 30 31NAME TYPE VALUE 32------------------------------------ ----------- ------------------------------ 33optimizer_capture_sql_plan_baselines boolean TRUE 34optimizer_use_sql_plan_baselines boolean TRUE 35 36LHR@dlhr> ALTER SYSTEM SET OPTIMIZER_CAPTURE_SQL_PLAN_BASELINES=FALSE; 37 38System altered.
--创建表并插入数据,脚本:
1CREATE TABLE tb_spm_test_lhr ( 2 id NUMBER, 3 description VARCHAR2(50) 4); 5 6DECLARE 7 TYPE t_tab IS TABLE OF tb_spm_test_lhr%ROWTYPE; 8 l_tab t_tab := t_TAB(); 9BEGIN10 FOR i IN 1 .. 10000 LOOP11 l_tab.extend;12 l_tab(l_tab.last).id := i;13 l_tab(l_tab.last).description := 'Description for ' || i;14 END LOOP;1516 FORALL i IN l_tab.first .. l_tab.last17 INSERT INTO tb_spm_test_lhr VALUES l_tab(i);1819 COMMIT;20 END;21 /222324EXEC DBMS_STATS.gather_table_stats(USER, 'tb_spm_test_lhr', cascade=>TRUE);2526set autot trace27SELECT description FROM tb_spm_test_lhr WHERE id = 100;CREATE TABLE tb_spm_test_lhr ( 2 id NUMBER, 3 description VARCHAR2(50) 4); 5 6DECLARE 7 TYPE t_tab IS TABLE OF tb_spm_test_lhr%ROWTYPE; 8 l_tab t_tab := t_TAB(); 9BEGIN 10 FOR i IN 1 .. 10000 LOOP 11 l_tab.extend; 12 l_tab(l_tab.last).id := i; 13 l_tab(l_tab.last).description := 'Description for ' || i; 14 END LOOP; 15 16 FORALL i IN l_tab.first .. l_tab.last 17 INSERT INTO tb_spm_test_lhr VALUES l_tab(i); 18 19 COMMIT; 20 END; 21 / 22 23 24EXEC DBMS_STATS.gather_table_stats(USER, 'tb_spm_test_lhr', cascade=>TRUE); 25 26set autot trace 27SELECT description FROM tb_spm_test_lhr WHERE id = 100;
开始执行:
1LHR@dlhr> CREATE TABLE tb_spm_test_lhr ( 2 2 id NUMBER, 3 3 description VARCHAR2(50) 4 4 ); 5 6Table created. 7 8LHR@dlhr> 9LHR@dlhr> DECLARE10 2 TYPE t_tab IS TABLE OF tb_spm_test_lhr%ROWTYPE;11 3 l_tab t_tab := t_TAB();12 4 BEGIN13 5 FOR i IN 1 .. 10000 LOOP14 6 l_tab.extend;15 7 l_tab(l_tab.last).id := i;16 8 l_tab(l_tab.last).description := 'Description for ' || i;17 9 END LOOP;18 10 19 11 FORALL i IN l_tab.first .. l_tab.last20 12 INSERT INTO tb_spm_test_lhr VALUES l_tab(i);21 13 22 14 COMMIT;23 15 END;24 16 /2526PL/SQL procedure successfully completed.272829LHR@dlhr> set autot trace30LHR@dlhr> SELECT description FROM tb_spm_test_lhr WHERE id = 100;313233Execution Plan34----------------------------------------------------------35Plan hash value: 21965616293637-------------------------------------------------------------------------------------38| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |39-------------------------------------------------------------------------------------40| 0 | SELECT STATEMENT | | 1 | 40 | 13 (0)| 00:00:01 |41|* 1 | TABLE ACCESS FULL| TB_SPM_TEST_LHR | 1 | 40 | 13 (0)| 00:00:01 |42-------------------------------------------------------------------------------------4344Predicate Information (identified by operation id):45---------------------------------------------------4647 1 - filter("ID"=100)4849Note50-----51 - dynamic sampling used for this statement (level=2)525354Statistics55----------------------------------------------------------56 4 recursive calls57 0 db block gets58 94 consistent gets59 0 physical reads60 0 redo size61 546 bytes sent via SQL*Net to client62 519 bytes received via SQL*Net from client63 2 SQL*Net roundtrips to/from client64 0 sorts (memory)65 0 sorts (disk)66 1 rows processedCREATE TABLE tb_spm_test_lhr ( 2 2 id NUMBER, 3 3 description VARCHAR2(50) 4 4 ); 5 6Table created. 7 8LHR@dlhr> 9LHR@dlhr> DECLARE 10 2 TYPE t_tab IS TABLE OF tb_spm_test_lhr%ROWTYPE; 11 3 l_tab t_tab := t_TAB(); 12 4 BEGIN 13 5 FOR i IN 1 .. 10000 LOOP 14 6 l_tab.extend; 15 7 l_tab(l_tab.last).id := i; 16 8 l_tab(l_tab.last).description := 'Description for ' || i; 17 9 END LOOP; 18 10 19 11 FORALL i IN l_tab.first .. l_tab.last 20 12 INSERT INTO tb_spm_test_lhr VALUES l_tab(i); 21 13 22 14 COMMIT; 23 15 END; 24 16 / 25 26PL/SQL procedure successfully completed. 27 28 29LHR@dlhr> set autot trace 30LHR@dlhr> SELECT description FROM tb_spm_test_lhr WHERE id = 100; 31 32 33Execution Plan 34---------------------------------------------------------- 35Plan hash value: 2196561629 36 37------------------------------------------------------------------------------------- 38| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | 39------------------------------------------------------------------------------------- 40| 0 | SELECT STATEMENT | | 1 | 40 | 13 (0)| 00:00:01 | 41|* 1 | TABLE ACCESS FULL| TB_SPM_TEST_LHR | 1 | 40 | 13 (0)| 00:00:01 | 42------------------------------------------------------------------------------------- 43 44Predicate Information (identified by operation id): 45--------------------------------------------------- 46 47 1 - filter("ID"=100) 48 49Note 50----- 51 - dynamic sampling used for this statement (level=2) 52 53 54Statistics 55---------------------------------------------------------- 56 4 recursive calls 57 0 db block gets 58 94 consistent gets 59 0 physical reads 60 0 redo size 61 546 bytes sent via SQL*Net to client 62 519 bytes received via SQL*Net from client 63 2 SQL*Net roundtrips to/from client 64 0 sorts (memory) 65 0 sorts (disk) 66 1 rows processed
获取刚才查询的SQL_ID:
1set autot off 2col SQL_TEXT format a100 3select distinct a.SQL_ID,a.SQL_TEXT from v$sql a 4WHERE a.SQL_TEXT like '%SELECT description FROM tb_spm_test_lhr WHERE id = 100%' 5and a.SQL_TEXT not like '%v$sql%' 6AND sql_text NOT LIKE '%EXPLAIN%'; 7 8LHR@dlhr> set autot off 9LHR@dlhr> col SQL_TEXT format a100 10LHR@dlhr> select distinct a.SQL_ID,a.SQL_TEXT from v$sql a 11 2 WHERE a.SQL_TEXT like '%SELECT description FROM tb_spm_test_lhr WHERE id = 100%' 12 3 and a.SQL_TEXT not like '%v$sql%' 13 4 AND sql_text NOT LIKE '%EXPLAIN%'; 14 15SQL_ID SQL_TEXT 16------------- ---------------------------------------------------------------------------------------------------- 17garkwg3yy2ram SELECT description FROM tb_spm_test_lhr WHERE id = 100 18 19----使用SQL_ID 从cursor cache中手工捕获执行计划: 20SET SERVEROUTPUT ON 21DECLARE 22 l_plans_loaded PLS_INTEGER; 23BEGIN 24 l_plans_loaded := DBMS_SPM.load_plans_from_cursor_cache( 25 sql_id => '&sql_id'); 26 DBMS_OUTPUT.put_line('Plans Loaded: ' || l_plans_loaded); 27END; 28/ 29-- --使用DBA_SQL_PLAN_BASELINES视图查看SPM 信息: 30col sql_handle for a35 31col plan_name for a35 32set lin 300 33SELECT SQL_HANDLE,plan_name,origin,enabled,accepted,fixed 34FROM dba_sql_plan_baselines 35WHERE sql_text LIKE '%tb_spm_test_lhr%' 36AND sql_text NOT LIKE'%dba_sql_plan_baselines%'; 37 38--刷新Share Pool,使下次SQL 执行时必须进行硬解析: 39ALTER SYSTEM FLUSH SHARED_POOL; 40 41LHR@dlhr> SET SERVEROUTPUT ON 42LHR@dlhr> DECLARE 43 2 l_plans_loaded PLS_INTEGER; 44 3 BEGIN 45 4 l_plans_loaded := DBMS_SPM.load_plans_from_cursor_cache( 46 5 sql_id => '&sql_id'); 47 6 DBMS_OUTPUT.put_line('Plans Loaded: ' || l_plans_loaded); 48 7 END; 49 8 / 50Enter value for sql_id: garkwg3yy2ram 51old 5: sql_id => '&sql_id'); 52new 5: sql_id => 'garkwg3yy2ram'); 53Plans Loaded: 1 54 55PL/SQL procedure successfully completed. 56 57 58LHR@dlhr> col sql_handle for a35 59LHR@dlhr> col plan_name for a35 60LHR@dlhr> set lin 300 61LHR@dlhr> SELECT sql_handle, plan_name,enabled, accepted 62 2 FROM dba_sql_plan_baselines 63 3 WHERE sql_text LIKE '%tb_spm_test_lhr%' 64 4 AND sql_text NOT LIKE'%dba_sql_plan_baselines%'; 65 66SQL_HANDLE PLAN_NAME ENA ACC 67----------------------------------- ----------------------------------- --- --- 68SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws3184920d2 YES YES 69 70LHR@dlhr> ALTER SYSTEM FLUSH SHARED_POOL; 71 72System altered. 73 74LHR@dlhr> set autot trace 75SELECT description FROM tb_spm_test_lhr WHERE id = 100; 76LHR@dlhr> 77 78Execution Plan 79---------------------------------------------------------- 80Plan hash value: 2196561629 81 82------------------------------------------------------------------------------------- 83| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | 84------------------------------------------------------------------------------------- 85| 0 | SELECT STATEMENT | | 1 | 40 | 13 (0)| 00:00:01 | 86|* 1 | TABLE ACCESS FULL| TB_SPM_TEST_LHR | 1 | 40 | 13 (0)| 00:00:01 | 87------------------------------------------------------------------------------------- 88 89Predicate Information (identified by operation id): 90--------------------------------------------------- 91 92 1 - filter("ID"=100) 93 94Note 95----- 96 - dynamic sampling used for this statement (level=2) 97 - SQL plan baseline "SQL_PLAN_4y6fmtxbvwws3184920d2" used for this statement 98 99100Statistics101----------------------------------------------------------102 555 recursive calls103 16 db block gets104 667 consistent gets105 0 physical reads106 3056 redo size107 546 bytes sent via SQL*Net to client108 519 bytes received via SQL*Net from client109 2 SQL*Net roundtrips to/from client110 32 sorts (memory)111 0 sorts (disk)112 1 rows processed113114115--创建索引,收集统计信息,并查询相同的SQL:116CREATE INDEX spm_test_tab_idx ON tb_spm_test_lhr(id);117EXEC DBMS_STATS.gather_table_stats(USER,'tb_spm_test_lhr', cascade=>TRUE);118119set autot trace120SELECT description FROM tb_spm_test_lhr WHERE id = 100;121122123LHR@dlhr> CREATE INDEX spm_test_tab_idx ON tb_spm_test_lhr(id);124Index created.125126LHR@dlhr> EXEC DBMS_STATS.gather_table_stats(USER,'tb_spm_test_lhr', cascade=>TRUE);127128129PL/SQL procedure successfully completed.130131LHR@dlhr> 132LHR@dlhr> 133LHR@dlhr> 134LHR@dlhr> set autot trace135LHR@dlhr> SELECT description FROM tb_spm_test_lhr WHERE id = 100;136137138139Execution Plan140----------------------------------------------------------141Plan hash value: 2196561629142143-------------------------------------------------------------------------------------144| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |145-------------------------------------------------------------------------------------146| 0 | SELECT STATEMENT | | 1 | 25 | 13 (0)| 00:00:01 |147|* 1 | TABLE ACCESS FULL| TB_SPM_TEST_LHR | 1 | 25 | 13 (0)| 00:00:01 |148-------------------------------------------------------------------------------------149150Predicate Information (identified by operation id):151---------------------------------------------------152153 1 - filter("ID"=100)154155Note156-----157 - SQL plan baseline "SQL_PLAN_4y6fmtxbvwws3184920d2" used for this statement158159160Statistics161----------------------------------------------------------162 640 recursive calls163 39 db block gets164 493 consistent gets165 2 physical reads166 12268 redo size167 546 bytes sent via SQL*Net to client168 519 bytes received via SQL*Net from client169 2 SQL*Net roundtrips to/from client170 10 sorts (memory)171 0 sorts (disk)172 1 rows processed173174175--这里我们创建了索引,但是这里还是走的全表扫描,这里使用索引明显才是最优的方案。176--查看SPM 视图:177set autot off178col sql_handle for a35179col plan_name for a35180set lin 300181SELECT SQL_HANDLE,plan_name,origin,enabled,accepted,fixed182FROM dba_sql_plan_baselines183WHERE sql_text LIKE '%tb_spm_test_lhr%'184AND sql_text NOT LIKE'%dba_sql_plan_baselines%';185186LHR@dlhr> set autot off187LHR@dlhr> col sql_handle for a35188LHR@dlhr> col plan_name for a35189LHR@dlhr> set lin 300190LHR@dlhr> SELECT sql_handle, plan_name,enabled, accepted191 2 FROM dba_sql_plan_baselines192 3 WHERE sql_text LIKE '%tb_spm_test_lhr%'193 4 AND sql_text NOT LIKE'%dba_sql_plan_baselines%';194195SQL_HANDLE PLAN_NAME ENA ACC196----------------------------------- ----------------------------------- --- ---197SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws3184920d2 YES YES198SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws38b725570 YES NO199200--通过BASELINES查询的结果,可以看到SQL产生了两条执行计划,但是最优的执行计划并没有被标记为ACCEPT,所以没有使用。201--下边我们演化执行计划:演化就是将cost低的执行计划标记为accept:202LHR@dlhr> SET LONG 10000203LHR@dlhr> SELECT DBMS_SPM.evolve_sql_plan_baseline(sql_handle => '&sql_handle') FROM dual;204Enter value for sql_handle: SQL_4f19d3cf57be7303205old 1: SELECT DBMS_SPM.evolve_sql_plan_baseline(sql_handle => '&sql_handle') FROM dual206new 1: SELECT DBMS_SPM.evolve_sql_plan_baseline(sql_handle => 'SQL_4f19d3cf57be7303') FROM dual207208DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE(SQL_HANDLE=>'SQL_4F19D3CF57BE7303')209--------------------------------------------------------------------------------210211-------------------------------------------------------------------------------212 Evolve SQL Plan Baseline Report213-------------------------------------------------------------------------------214215Inputs:216-------217 SQL_HANDLE = SQL_4f19d3cf57be7303218 PLAN_NAME =219 TIME_LIMIT = DBMS_SPM.AUTO_LIMIT220 VERIFY = YES221 COMMIT = YES222223Plan: SQL_PLAN_4y6fmtxbvwws38b725570224------------------------------------225 Plan was verified: Time used .018 seconds.226 Plan passed performance criterion: 15 times better than baseline plan.227 Plan was changed to an accepted plan.228229 Baseline Plan Test Plan Stats Ratio230 ------------- --------- -----------231 Execution Status: COMPLETE COMPLETE232 Rows Processed: 1 1233 Elapsed Time(ms): .308 .025 12.32234 CPU Time(ms): .164 .015 10.93235 Buffer Gets: 45 3 15236 Physical Read Requests: 0 0237 Physical Write Requests: 0 0238 Physical Read Bytes: 0 0239 Physical Write Bytes: 0 0240 Executions: 1 1241242-------------------------------------------------------------------------------243 Report Summary244-------------------------------------------------------------------------------245Number of plans verified: 1246Number of plans accepted: 1247248249--再次查看DBA_SQL_PLAN_BASELINES视图:250set autot off251col sql_handle for a35252col plan_name for a35253set lin 300254SELECT SQL_HANDLE,plan_name,origin,enabled,accepted,fixed255FROM dba_sql_plan_baselines256WHERE sql_text LIKE '%tb_spm_test_lhr%'257AND sql_text NOT LIKE'%dba_sql_plan_baselines%';258259LHR@dlhr> set autot off260LHR@dlhr> col sql_handle for a35261LHR@dlhr> col plan_name for a35262LHR@dlhr> set lin 300263LHR@dlhr> SELECT sql_handle, plan_name,enabled, accepted264 2 FROM dba_sql_plan_baselines265 3 WHERE sql_text LIKE '%tb_spm_test_lhr%'266 4 AND sql_text NOT LIKE'%dba_sql_plan_baselines%';267268SQL_HANDLE PLAN_NAME ENA ACC269----------------------------------- ----------------------------------- --- ---270SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws3184920d2 YES YES271SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws38b725570 YES YES272273--再次执行SQL:274set autot trace275SELECT description FROM tb_spm_test_lhr WHERE id = 100;276277LHR@dlhr> set autot trace278LHR@dlhr> SELECT description FROM tb_spm_test_lhr WHERE id = 100;279280281Execution Plan282----------------------------------------------------------283Plan hash value: 2587945646284285------------------------------------------------------------------------------------------------286| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |287------------------------------------------------------------------------------------------------288| 0 | SELECT STATEMENT | | 1 | 25 | 2 (0)| 00:00:01 |289| 1 | TABLE ACCESS BY INDEX ROWID| TB_SPM_TEST_LHR | 1 | 25 | 2 (0)| 00:00:01 |290|* 2 | INDEX RANGE SCAN | SPM_TEST_TAB_IDX | 1 | | 1 (0)| 00:00:01 |291------------------------------------------------------------------------------------------------292293Predicate Information (identified by operation id):294---------------------------------------------------295296 2 - access("ID"=100)297298Note299-----300 - SQL plan baseline "SQL_PLAN_4y6fmtxbvwws38b725570" used for this statement301302303Statistics304----------------------------------------------------------305 13 recursive calls306 14 db block gets307 18 consistent gets308 0 physical reads309 3048 redo size310 553 bytes sent via SQL*Net to client311 519 bytes received via SQL*Net from client312 2 SQL*Net roundtrips to/from client313 0 sorts (memory)314 0 sorts (disk)315 1 rows processedset autot off 2col SQL_TEXT format a100 3select distinct a.SQL_ID,a.SQL_TEXT from v$sql a 4WHERE a.SQL_TEXT like '%SELECT description FROM tb_spm_test_lhr WHERE id = 100%' 5and a.SQL_TEXT not like '%v$sql%' 6AND sql_text NOT LIKE '%EXPLAIN%'; 7 8LHR@dlhr> set autot off 9LHR@dlhr> col SQL_TEXT format a100 10LHR@dlhr> select distinct a.SQL_ID,a.SQL_TEXT from v$sql a 11 2 WHERE a.SQL_TEXT like '%SELECT description FROM tb_spm_test_lhr WHERE id = 100%' 12 3 and a.SQL_TEXT not like '%v$sql%' 13 4 AND sql_text NOT LIKE '%EXPLAIN%'; 14 15SQL_ID SQL_TEXT 16------------- ---------------------------------------------------------------------------------------------------- 17garkwg3yy2ram SELECT description FROM tb_spm_test_lhr WHERE id = 100 18 19----使用SQL_ID 从cursor cache中手工捕获执行计划: 20SET SERVEROUTPUT ON 21DECLARE 22 l_plans_loaded PLS_INTEGER; 23BEGIN 24 l_plans_loaded := DBMS_SPM.load_plans_from_cursor_cache( 25 sql_id => '&sql_id'); 26 DBMS_OUTPUT.put_line('Plans Loaded: ' || l_plans_loaded); 27END; 28/ 29-- --使用DBA_SQL_PLAN_BASELINES视图查看SPM 信息: 30col sql_handle for a35 31col plan_name for a35 32set lin 300 33SELECT SQL_HANDLE,plan_name,origin,enabled,accepted,fixed 34FROM dba_sql_plan_baselines 35WHERE sql_text LIKE '%tb_spm_test_lhr%' 36AND sql_text NOT LIKE'%dba_sql_plan_baselines%'; 37 38--刷新Share Pool,使下次SQL 执行时必须进行硬解析: 39ALTER SYSTEM FLUSH SHARED_POOL; 40 41LHR@dlhr> SET SERVEROUTPUT ON 42LHR@dlhr> DECLARE 43 2 l_plans_loaded PLS_INTEGER; 44 3 BEGIN 45 4 l_plans_loaded := DBMS_SPM.load_plans_from_cursor_cache( 46 5 sql_id => '&sql_id'); 47 6 DBMS_OUTPUT.put_line('Plans Loaded: ' || l_plans_loaded); 48 7 END; 49 8 / 50Enter value for sql_id: garkwg3yy2ram 51old 5: sql_id => '&sql_id'); 52new 5: sql_id => 'garkwg3yy2ram'); 53Plans Loaded: 1 54 55PL/SQL procedure successfully completed. 56 57 58LHR@dlhr> col sql_handle for a35 59LHR@dlhr> col plan_name for a35 60LHR@dlhr> set lin 300 61LHR@dlhr> SELECT sql_handle, plan_name,enabled, accepted 62 2 FROM dba_sql_plan_baselines 63 3 WHERE sql_text LIKE '%tb_spm_test_lhr%' 64 4 AND sql_text NOT LIKE'%dba_sql_plan_baselines%'; 65 66SQL_HANDLE PLAN_NAME ENA ACC 67----------------------------------- ----------------------------------- --- --- 68SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws3184920d2 YES YES 69 70LHR@dlhr> ALTER SYSTEM FLUSH SHARED_POOL; 71 72System altered. 73 74LHR@dlhr> set autot trace 75SELECT description FROM tb_spm_test_lhr WHERE id = 100; 76LHR@dlhr> 77 78Execution Plan 79---------------------------------------------------------- 80Plan hash value: 2196561629 81 82------------------------------------------------------------------------------------- 83| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | 84------------------------------------------------------------------------------------- 85| 0 | SELECT STATEMENT | | 1 | 40 | 13 (0)| 00:00:01 | 86|* 1 | TABLE ACCESS FULL| TB_SPM_TEST_LHR | 1 | 40 | 13 (0)| 00:00:01 | 87------------------------------------------------------------------------------------- 88 89Predicate Information (identified by operation id): 90--------------------------------------------------- 91 92 1 - filter("ID"=100) 93 94Note 95----- 96 - dynamic sampling used for this statement (level=2) 97 - SQL plan baseline "SQL_PLAN_4y6fmtxbvwws3184920d2" used for this statement 98 99 100Statistics 101---------------------------------------------------------- 102 555 recursive calls 103 16 db block gets 104 667 consistent gets 105 0 physical reads 106 3056 redo size 107 546 bytes sent via SQL*Net to client 108 519 bytes received via SQL*Net from client 109 2 SQL*Net roundtrips to/from client 110 32 sorts (memory) 111 0 sorts (disk) 112 1 rows processed 113 114 115--创建索引,收集统计信息,并查询相同的SQL: 116CREATE INDEX spm_test_tab_idx ON tb_spm_test_lhr(id); 117EXEC DBMS_STATS.gather_table_stats(USER,'tb_spm_test_lhr', cascade=>TRUE); 118 119set autot trace 120SELECT description FROM tb_spm_test_lhr WHERE id = 100; 121 122 123LHR@dlhr> CREATE INDEX spm_test_tab_idx ON tb_spm_test_lhr(id); 124Index created. 125 126LHR@dlhr> EXEC DBMS_STATS.gather_table_stats(USER,'tb_spm_test_lhr', cascade=>TRUE); 127 128 129PL/SQL procedure successfully completed. 130 131LHR@dlhr> 132LHR@dlhr> 133LHR@dlhr> 134LHR@dlhr> set autot trace 135LHR@dlhr> SELECT description FROM tb_spm_test_lhr WHERE id = 100; 136 137 138 139Execution Plan 140---------------------------------------------------------- 141Plan hash value: 2196561629 142 143------------------------------------------------------------------------------------- 144| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | 145------------------------------------------------------------------------------------- 146| 0 | SELECT STATEMENT | | 1 | 25 | 13 (0)| 00:00:01 | 147|* 1 | TABLE ACCESS FULL| TB_SPM_TEST_LHR | 1 | 25 | 13 (0)| 00:00:01 | 148------------------------------------------------------------------------------------- 149 150Predicate Information (identified by operation id): 151--------------------------------------------------- 152 153 1 - filter("ID"=100) 154 155Note 156----- 157 - SQL plan baseline "SQL_PLAN_4y6fmtxbvwws3184920d2" used for this statement 158 159 160Statistics 161---------------------------------------------------------- 162 640 recursive calls 163 39 db block gets 164 493 consistent gets 165 2 physical reads 166 12268 redo size 167 546 bytes sent via SQL*Net to client 168 519 bytes received via SQL*Net from client 169 2 SQL*Net roundtrips to/from client 170 10 sorts (memory) 171 0 sorts (disk) 172 1 rows processed 173 174 175--这里我们创建了索引,但是这里还是走的全表扫描,这里使用索引明显才是最优的方案。 176--查看SPM 视图: 177set autot off 178col sql_handle for a35 179col plan_name for a35 180set lin 300 181SELECT SQL_HANDLE,plan_name,origin,enabled,accepted,fixed 182FROM dba_sql_plan_baselines 183WHERE sql_text LIKE '%tb_spm_test_lhr%' 184AND sql_text NOT LIKE'%dba_sql_plan_baselines%'; 185 186LHR@dlhr> set autot off 187LHR@dlhr> col sql_handle for a35 188LHR@dlhr> col plan_name for a35 189LHR@dlhr> set lin 300 190LHR@dlhr> SELECT sql_handle, plan_name,enabled, accepted 191 2 FROM dba_sql_plan_baselines 192 3 WHERE sql_text LIKE '%tb_spm_test_lhr%' 193 4 AND sql_text NOT LIKE'%dba_sql_plan_baselines%'; 194 195SQL_HANDLE PLAN_NAME ENA ACC 196----------------------------------- ----------------------------------- --- --- 197SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws3184920d2 YES YES 198SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws38b725570 YES NO 199 200--通过BASELINES查询的结果,可以看到SQL产生了两条执行计划,但是最优的执行计划并没有被标记为ACCEPT,所以没有使用。 201--下边我们演化执行计划:演化就是将cost低的执行计划标记为accept: 202LHR@dlhr> SET LONG 10000 203LHR@dlhr> SELECT DBMS_SPM.evolve_sql_plan_baseline(sql_handle => '&sql_handle') FROM dual; 204Enter value for sql_handle: SQL_4f19d3cf57be7303 205old 1: SELECT DBMS_SPM.evolve_sql_plan_baseline(sql_handle => '&sql_handle') FROM dual 206new 1: SELECT DBMS_SPM.evolve_sql_plan_baseline(sql_handle => 'SQL_4f19d3cf57be7303') FROM dual 207 208DBMS_SPM.EVOLVE_SQL_PLAN_BASELINE(SQL_HANDLE=>'SQL_4F19D3CF57BE7303') 209-------------------------------------------------------------------------------- 210 211------------------------------------------------------------------------------- 212 Evolve SQL Plan Baseline Report 213------------------------------------------------------------------------------- 214 215Inputs: 216------- 217 SQL_HANDLE = SQL_4f19d3cf57be7303 218 PLAN_NAME = 219 TIME_LIMIT = DBMS_SPM.AUTO_LIMIT 220 VERIFY = YES 221 COMMIT = YES 222 223Plan: SQL_PLAN_4y6fmtxbvwws38b725570 224------------------------------------ 225 Plan was verified: Time used .018 seconds. 226 Plan passed performance criterion: 15 times better than baseline plan. 227 Plan was changed to an accepted plan. 228 229 Baseline Plan Test Plan Stats Ratio 230 ------------- --------- ----------- 231 Execution Status: COMPLETE COMPLETE 232 Rows Processed: 1 1 233 Elapsed Time(ms): .308 .025 12.32 234 CPU Time(ms): .164 .015 10.93 235 Buffer Gets: 45 3 15 236 Physical Read Requests: 0 0 237 Physical Write Requests: 0 0 238 Physical Read Bytes: 0 0 239 Physical Write Bytes: 0 0 240 Executions: 1 1 241 242------------------------------------------------------------------------------- 243 Report Summary 244------------------------------------------------------------------------------- 245Number of plans verified: 1 246Number of plans accepted: 1 247 248 249--再次查看DBA_SQL_PLAN_BASELINES视图: 250set autot off 251col sql_handle for a35 252col plan_name for a35 253set lin 300 254SELECT SQL_HANDLE,plan_name,origin,enabled,accepted,fixed 255FROM dba_sql_plan_baselines 256WHERE sql_text LIKE '%tb_spm_test_lhr%' 257AND sql_text NOT LIKE'%dba_sql_plan_baselines%'; 258 259LHR@dlhr> set autot off 260LHR@dlhr> col sql_handle for a35 261LHR@dlhr> col plan_name for a35 262LHR@dlhr> set lin 300 263LHR@dlhr> SELECT sql_handle, plan_name,enabled, accepted 264 2 FROM dba_sql_plan_baselines 265 3 WHERE sql_text LIKE '%tb_spm_test_lhr%' 266 4 AND sql_text NOT LIKE'%dba_sql_plan_baselines%'; 267 268SQL_HANDLE PLAN_NAME ENA ACC 269----------------------------------- ----------------------------------- --- --- 270SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws3184920d2 YES YES 271SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws38b725570 YES YES 272 273--再次执行SQL: 274set autot trace 275SELECT description FROM tb_spm_test_lhr WHERE id = 100; 276 277LHR@dlhr> set autot trace 278LHR@dlhr> SELECT description FROM tb_spm_test_lhr WHERE id = 100; 279 280 281Execution Plan 282---------------------------------------------------------- 283Plan hash value: 2587945646 284 285------------------------------------------------------------------------------------------------ 286| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | 287------------------------------------------------------------------------------------------------ 288| 0 | SELECT STATEMENT | | 1 | 25 | 2 (0)| 00:00:01 | 289| 1 | TABLE ACCESS BY INDEX ROWID| TB_SPM_TEST_LHR | 1 | 25 | 2 (0)| 00:00:01 | 290|* 2 | INDEX RANGE SCAN | SPM_TEST_TAB_IDX | 1 | | 1 (0)| 00:00:01 | 291------------------------------------------------------------------------------------------------ 292 293Predicate Information (identified by operation id): 294--------------------------------------------------- 295 296 2 - access("ID"=100) 297 298Note 299----- 300 - SQL plan baseline "SQL_PLAN_4y6fmtxbvwws38b725570" used for this statement 301 302 303Statistics 304---------------------------------------------------------- 305 13 recursive calls 306 14 db block gets 307 18 consistent gets 308 0 physical reads 309 3048 redo size 310 553 bytes sent via SQL*Net to client 311 519 bytes received via SQL*Net from client 312 2 SQL*Net roundtrips to/from client 313 0 sorts (memory) 314 0 sorts (disk) 315 1 rows processed
这次正确的使用了索引。因为只有标记为ENABLE和ACCEPT的plan才可以被使用。
下面示例将我们的第一个走全表扫描的执行计划标记为fixed。标记为fixed的执行计划会被优先使用。FIXED表示优化程序仅考虑标记为FIXED的计划,而不考虑其它计划。例如,如果有10个基线计划,其中的三个计划被标记为FIXED,则优化程序将仅使用这三个计划中的最佳计划,而忽略其它所有计划。如果某个SQL计划基线至少包含一个已启用的已修复计划,则该SQL计划基线就是FIXED的。如果在修复的SQL计划基线中添加了新计划,则在手动将这些新计划声明为FIXED之前,无法使用这些新计划。
1set autot off 2select * from table(dbms_xplan.display_sql_plan_baseline (sql_handle => '&sql_handle', format => 'basic')); 3 4SET SERVEROUTPUT ON 5DECLARE 6 l_plans_altered PLS_INTEGER; 7BEGIN 8 l_plans_altered := DBMS_SPM.alter_sql_plan_baseline( 9 sql_handle => '&sql_handle', 10 plan_name => '&plan_name', 11 attribute_name => 'fixed', 12 attribute_value => 'YES'); 13 14 DBMS_OUTPUT.put_line('Plans Altered: ' || l_plans_altered); 15END; 16/ 17 18LHR@dlhr> SET SERVEROUTPUT ON 19LHR@dlhr> DECLARE 20 2 l_plans_altered PLS_INTEGER; 21 3 BEGIN 22 4 l_plans_altered := DBMS_SPM.alter_sql_plan_baseline( 23 5 sql_handle => '&sql_handle', 24 6 plan_name => '&plan_name', 25 7 attribute_name => 'fixed', 26 8 attribute_value => 'YES'); 27 9 28 10 DBMS_OUTPUT.put_line('Plans Altered: ' || l_plans_altered); 29 11 END; 30 12 / 31Enter value for sql_handle: SQL_4f19d3cf57be7303 32old 5: sql_handle => '&sql_handle', 33new 5: sql_handle => 'SQL_4f19d3cf57be7303', 34Enter value for plan_name: SQL_PLAN_4y6fmtxbvwws3184920d2 35old 6: plan_name => '&plan_name', 36new 6: plan_name => 'SQL_PLAN_4y6fmtxbvwws3184920d2', 37Plans Altered: 1 38 39PL/SQL procedure successfully completed. 40 41--验证: 42set autot off 43col sql_handle for a35 44col plan_name for a35 45set lin 300 46SELECT SQL_HANDLE,plan_name,origin,enabled,accepted,fixed 47FROM dba_sql_plan_baselines 48WHERE sql_text LIKE '%tb_spm_test_lhr%' 49AND sql_text NOT LIKE'%dba_sql_plan_baselines%'; 50 51LHR@dlhr> set autot off 52LHR@dlhr> select * from table(dbms_xplan.display_sql_plan_baseline (sql_handle => '&sql_handle', format => 'basic')); 53Enter value for sql_handle: SQL_4f19d3cf57be7303 54old 1: select * from table(dbms_xplan.display_sql_plan_baseline (sql_handle => '&sql_handle', format => 'basic')) 55new 1: select * from table(dbms_xplan.display_sql_plan_baseline (sql_handle => 'SQL_4f19d3cf57be7303', format => 'basic')) 56 57PLAN_TABLE_OUTPUT 58-------------------------------------------------------------------------------------- 59 60-------------------------------------------------------------------------------- 61SQL handle: SQL_4f19d3cf57be7303 62SQL text: SELECT description FROM tb_spm_test_lhr WHERE id = 100 63-------------------------------------------------------------------------------- 64 65-------------------------------------------------------------------------------- 66Plan name: SQL_PLAN_4y6fmtxbvwws3184920d2 Plan id: 407445714 67Enabled: YES Fixed: YES Accepted: YES Origin: MANUAL-LOAD 68-------------------------------------------------------------------------------- 69 70Plan hash value: 2196561629 71 72--------------------------------------------- 73| Id | Operation | Name | 74--------------------------------------------- 75| 0 | SELECT STATEMENT | | 76| 1 | TABLE ACCESS FULL| TB_SPM_TEST_LHR | 77--------------------------------------------- 78 79-------------------------------------------------------------------------------- 80Plan name: SQL_PLAN_4y6fmtxbvwws38b725570 Plan id: 2339526000 81Enabled: YES Fixed: NO Accepted: YES Origin: AUTO-CAPTURE 82-------------------------------------------------------------------------------- 83 84Plan hash value: 2587945646 85 86-------------------------------------------------------- 87| Id | Operation | Name | 88-------------------------------------------------------- 89| 0 | SELECT STATEMENT | | 90| 1 | TABLE ACCESS BY INDEX ROWID| TB_SPM_TEST_LHR | 91| 2 | INDEX RANGE SCAN | SPM_TEST_TAB_IDX | 92-------------------------------------------------------- 93 9434 rows selected. 95 96LHR@dlhr> set autot off 97LHR@dlhr> col sql_handle for a35 98LHR@dlhr> col plan_name for a35 99LHR@dlhr> set lin 300100LHR@dlhr> SELECT SQL_HANDLE,plan_name,origin,enabled,accepted,fixed101 2 FROM dba_sql_plan_baselines102 3 WHERE sql_text LIKE '%tb_spm_test_lhr%'103 4 AND sql_text NOT LIKE'%dba_sql_plan_baselines%';104105SQL_HANDLE PLAN_NAME ORIGIN ENA ACC FIX106----------------------------------- ----------------------------------- -------------- --- --- ---107SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws3184920d2 MANUAL-LOAD YES YES YES108SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws38b725570 AUTO-CAPTURE YES YES NO109110111112--再次查看我们之前的SQL:113set autot trace114SELECT description FROM tb_spm_test_lhr WHERE id = 100;115116LHR@dlhr> set autot trace117LHR@dlhr> SELECT description FROM tb_spm_test_lhr WHERE id = 100;118119120Execution Plan121----------------------------------------------------------122Plan hash value: 2196561629123124-------------------------------------------------------------------------------------125| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |126-------------------------------------------------------------------------------------127| 0 | SELECT STATEMENT | | 1 | 25 | 13 (0)| 00:00:01 |128|* 1 | TABLE ACCESS FULL| TB_SPM_TEST_LHR | 1 | 25 | 13 (0)| 00:00:01 |129-------------------------------------------------------------------------------------130131Predicate Information (identified by operation id):132---------------------------------------------------133134 1 - filter("ID"=100)135136Note137-----138 - SQL plan baseline "SQL_PLAN_4y6fmtxbvwws3184920d2" used for this statement139140141Statistics142----------------------------------------------------------143 6 recursive calls144 8 db block gets145 46 consistent gets146 0 physical reads147 0 redo size148 546 bytes sent via SQL*Net to client149 519 bytes received via SQL*Net from client150 2 SQL*Net roundtrips to/from client151 0 sorts (memory)152 0 sorts (disk)153 1 rows processedset autot off 2select * from table(dbms_xplan.display_sql_plan_baseline (sql_handle => '&sql_handle', format => 'basic')); 3 4SET SERVEROUTPUT ON 5DECLARE 6 l_plans_altered PLS_INTEGER; 7BEGIN 8 l_plans_altered := DBMS_SPM.alter_sql_plan_baseline( 9 sql_handle => '&sql_handle', 10 plan_name => '&plan_name', 11 attribute_name => 'fixed', 12 attribute_value => 'YES'); 13 14 DBMS_OUTPUT.put_line('Plans Altered: ' || l_plans_altered); 15END; 16/ 17 18LHR@dlhr> SET SERVEROUTPUT ON 19LHR@dlhr> DECLARE 20 2 l_plans_altered PLS_INTEGER; 21 3 BEGIN 22 4 l_plans_altered := DBMS_SPM.alter_sql_plan_baseline( 23 5 sql_handle => '&sql_handle', 24 6 plan_name => '&plan_name', 25 7 attribute_name => 'fixed', 26 8 attribute_value => 'YES'); 27 9 28 10 DBMS_OUTPUT.put_line('Plans Altered: ' || l_plans_altered); 29 11 END; 30 12 / 31Enter value for sql_handle: SQL_4f19d3cf57be7303 32old 5: sql_handle => '&sql_handle', 33new 5: sql_handle => 'SQL_4f19d3cf57be7303', 34Enter value for plan_name: SQL_PLAN_4y6fmtxbvwws3184920d2 35old 6: plan_name => '&plan_name', 36new 6: plan_name => 'SQL_PLAN_4y6fmtxbvwws3184920d2', 37Plans Altered: 1 38 39PL/SQL procedure successfully completed. 40 41--验证: 42set autot off 43col sql_handle for a35 44col plan_name for a35 45set lin 300 46SELECT SQL_HANDLE,plan_name,origin,enabled,accepted,fixed 47FROM dba_sql_plan_baselines 48WHERE sql_text LIKE '%tb_spm_test_lhr%' 49AND sql_text NOT LIKE'%dba_sql_plan_baselines%'; 50 51LHR@dlhr> set autot off 52LHR@dlhr> select * from table(dbms_xplan.display_sql_plan_baseline (sql_handle => '&sql_handle', format => 'basic')); 53Enter value for sql_handle: SQL_4f19d3cf57be7303 54old 1: select * from table(dbms_xplan.display_sql_plan_baseline (sql_handle => '&sql_handle', format => 'basic')) 55new 1: select * from table(dbms_xplan.display_sql_plan_baseline (sql_handle => 'SQL_4f19d3cf57be7303', format => 'basic')) 56 57PLAN_TABLE_OUTPUT 58-------------------------------------------------------------------------------------- 59 60-------------------------------------------------------------------------------- 61SQL handle: SQL_4f19d3cf57be7303 62SQL text: SELECT description FROM tb_spm_test_lhr WHERE id = 100 63-------------------------------------------------------------------------------- 64 65-------------------------------------------------------------------------------- 66Plan name: SQL_PLAN_4y6fmtxbvwws3184920d2 Plan id: 407445714 67Enabled: YES Fixed: YES Accepted: YES Origin: MANUAL-LOAD 68-------------------------------------------------------------------------------- 69 70Plan hash value: 2196561629 71 72--------------------------------------------- 73| Id | Operation | Name | 74--------------------------------------------- 75| 0 | SELECT STATEMENT | | 76| 1 | TABLE ACCESS FULL| TB_SPM_TEST_LHR | 77--------------------------------------------- 78 79-------------------------------------------------------------------------------- 80Plan name: SQL_PLAN_4y6fmtxbvwws38b725570 Plan id: 2339526000 81Enabled: YES Fixed: NO Accepted: YES Origin: AUTO-CAPTURE 82-------------------------------------------------------------------------------- 83 84Plan hash value: 2587945646 85 86-------------------------------------------------------- 87| Id | Operation | Name | 88-------------------------------------------------------- 89| 0 | SELECT STATEMENT | | 90| 1 | TABLE ACCESS BY INDEX ROWID| TB_SPM_TEST_LHR | 91| 2 | INDEX RANGE SCAN | SPM_TEST_TAB_IDX | 92-------------------------------------------------------- 93 9434 rows selected. 95 96LHR@dlhr> set autot off 97LHR@dlhr> col sql_handle for a35 98LHR@dlhr> col plan_name for a35 99LHR@dlhr> set lin 300 100LHR@dlhr> SELECT SQL_HANDLE,plan_name,origin,enabled,accepted,fixed 101 2 FROM dba_sql_plan_baselines 102 3 WHERE sql_text LIKE '%tb_spm_test_lhr%' 103 4 AND sql_text NOT LIKE'%dba_sql_plan_baselines%'; 104 105SQL_HANDLE PLAN_NAME ORIGIN ENA ACC FIX 106----------------------------------- ----------------------------------- -------------- --- --- --- 107SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws3184920d2 MANUAL-LOAD YES YES YES 108SQL_4f19d3cf57be7303 SQL_PLAN_4y6fmtxbvwws38b725570 AUTO-CAPTURE YES YES NO 109 110 111 112--再次查看我们之前的SQL: 113set autot trace 114SELECT description FROM tb_spm_test_lhr WHERE id = 100; 115 116LHR@dlhr> set autot trace 117LHR@dlhr> SELECT description FROM tb_spm_test_lhr WHERE id = 100; 118 119 120Execution Plan 121---------------------------------------------------------- 122Plan hash value: 2196561629 123 124------------------------------------------------------------------------------------- 125| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | 126------------------------------------------------------------------------------------- 127| 0 | SELECT STATEMENT | | 1 | 25 | 13 (0)| 00:00:01 | 128|* 1 | TABLE ACCESS FULL| TB_SPM_TEST_LHR | 1 | 25 | 13 (0)| 00:00:01 | 129------------------------------------------------------------------------------------- 130 131Predicate Information (identified by operation id): 132--------------------------------------------------- 133 134 1 - filter("ID"=100) 135 136Note 137----- 138 - SQL plan baseline "SQL_PLAN_4y6fmtxbvwws3184920d2" used for this statement 139 140 141Statistics 142---------------------------------------------------------- 143 6 recursive calls 144 8 db block gets 145 46 consistent gets 146 0 physical reads 147 0 redo size 148 546 bytes sent via SQL*Net to client 149 519 bytes received via SQL*Net from client 150 2 SQL*Net roundtrips to/from client 151 0 sorts (memory) 152 0 sorts (disk) 153 1 rows processed
这里已经走了全表扫描,根据前边的示例,我们知道这里走索引会更优,但因为我们将走全表扫描的执行计划设置为fixed,所以优先使用这个执行计划。
标签:spm,610,sql,DB,dlhr,plan,SQL,id,SPM 来源: https://blog.51cto.com/lhrbest/2706634