在Oracle中，SQL概要（SQL Profile）的作用是什么？
♣答案部分
SQL Profile就是为某条SQL语句提供除了系统统计信息、对象（表和索引等）统计信息之外的其它信息，比如运行环境、额外的更准确的统计信息，以帮助优化器为SQL语句选择更适合的执行计划。SQL Profile可以说是Outline的进化。Outline能够实现的功能SQL Profile也完全能够实现，而SQL Profile具有Outline不具备的优化，最重要的有两点：①SQL Profile更容易生成、更改和控制。②SQL Profile在对SQL语句的支持上做得更好，也就是适用范围更广。
对于sqlprof_attr部分的数据可以使用脚本coe_xfr_sql_profile.sql脚本生成。
使用SQL Profile的两个目的：①锁定或者说是稳定执行计划。②在不能修改应用中的SQL的情况下使SQL语句按指定的执行计划运行。
SQL Profile最大的优点是在不修改SQL语句和会话执行环境的情况下去优化SQL的执行效率，适合无法在应用程序中修改SQL时。
SQL Profile对以下类型语句有效：
l SELECT语句；
l UPDATE语句；
l INSERT语句（仅当使用SELECT子句时有效）；
l DELETE语句；
l CREATE语句（仅当使用SELECT子句时有效）；
l MERGE语句（仅当作UPDATE和INSERT操作时有效）。
另外，使用SQL Profile还必须有CREATE ANY SQL PROFILE、DROP ANY SQL PROFILE和ALTER ANY SQL PROFILE等系统权限。
有两种生成SQL Profile的方法，分别是手动和采用STA来生成。
（一）SQL Profile使用示例--手工创建SQL Profile
创建测试表，根据DBA_OBJECTS创建，OBJECT_ID上有索引
1LHR@dlhr> select * from v$version; 2 3BANNER 4-------------------------------------------------------------------------------- 5Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production 6PL/SQL Release 11.2.0.4.0 - Production 7CORE 11.2.0.4.0 Production 8TNS for IBM/AIX RISC System/6000: Version 11.2.0.4.0 - Production 9NLSRTL Version 11.2.0.4.0 - Production1011LHR@dlhr> Create table TB_LHR_20160525 as select * from dba_objects;1213Table created.1415LHR@dlhr> create index IND_TB_LHR_ID on TB_LHR_20160525(object_id);1617Index created.select * from v$version; 2 3BANNER 4-------------------------------------------------------------------------------- 5Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production 6PL/SQL Release 11.2.0.4.0 - Production 7CORE 11.2.0.4.0 Production 8TNS for IBM/AIX RISC System/6000: Version 11.2.0.4.0 - Production 9NLSRTL Version 11.2.0.4.0 - Production 10 11LHR@dlhr> Create table TB_LHR_20160525 as select * from dba_objects; 12 13Table created. 14 15LHR@dlhr> create index IND_TB_LHR_ID on TB_LHR_20160525(object_id); 16 17Index created.
查看SQL默认执行计划，走了索引，通过指定Outline可以获取到系统为我们生成的hint
1LHR@dlhr> explain plan for select * from TB_LHR_20160525 where object_id= :a; 2 3Explained. 4 5LHR@dlhr> select * from table(dbms_xplan.display(null,null,'outline')); 6 7PLAN_TABLE_OUTPUT 8-------------------------------------------------------------------------------------------------------- 9Plan hash value: 42540501521011-----------------------------------------------------------------------------------------------12| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |13-----------------------------------------------------------------------------------------------14| 0 | SELECT STATEMENT | | 886 | 179K| 7 (0)| 00:00:01 |15| 1 | TABLE ACCESS BY INDEX ROWID| TB_LHR_20160525 | 886 | 179K| 7 (0)| 00:00:01 |16|* 2 | INDEX RANGE SCAN | IND_TB_LHR_ID | 354 | | 1 (0)| 00:00:01 |17-----------------------------------------------------------------------------------------------1819Outline Data20-------------2122 /*+23 BEGIN_OUTLINE_DATA24 INDEX_RS_ASC(@"SEL$1" "TB_LHR_20160525"@"SEL$1" ("TB_LHR_20160525"."OBJECT_ID"))25 OUTLINE_LEAF(@"SEL$1")26 ALL_ROWS27 DB_VERSION('11.2.0.4')28 OPTIMIZER_FEATURES_ENABLE('11.2.0.4')29 IGNORE_OPTIM_EMBEDDED_HINTS30 END_OUTLINE_DATA31 */3233Predicate Information (identified by operation id):34---------------------------------------------------3536 2 - access("OBJECT_ID"=TO_NUMBER(:A))3738Note39-----40 - dynamic sampling used for this statement (level=2)414232 rows selected.explain plan for select * from TB_LHR_20160525 where object_id= :a; 2 3Explained. 4 5LHR@dlhr> select * from table(dbms_xplan.display(null,null,'outline')); 6 7PLAN_TABLE_OUTPUT 8-------------------------------------------------------------------------------------------------------- 9Plan hash value: 4254050152 10 11----------------------------------------------------------------------------------------------- 12| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | 13----------------------------------------------------------------------------------------------- 14| 0 | SELECT STATEMENT | | 886 | 179K| 7 (0)| 00:00:01 | 15| 1 | TABLE ACCESS BY INDEX ROWID| TB_LHR_20160525 | 886 | 179K| 7 (0)| 00:00:01 | 16|* 2 | INDEX RANGE SCAN | IND_TB_LHR_ID | 354 | | 1 (0)| 00:00:01 | 17----------------------------------------------------------------------------------------------- 18 19Outline Data 20------------- 21 22 /*+ 23 BEGIN_OUTLINE_DATA 24 INDEX_RS_ASC(@"SEL$1" "TB_LHR_20160525"@"SEL$1" ("TB_LHR_20160525"."OBJECT_ID")) 25 OUTLINE_LEAF(@"SEL$1") 26 ALL_ROWS 27 DB_VERSION('11.2.0.4') 28 OPTIMIZER_FEATURES_ENABLE('11.2.0.4') 29 IGNORE_OPTIM_EMBEDDED_HINTS 30 END_OUTLINE_DATA 31 */ 32 33Predicate Information (identified by operation id): 34--------------------------------------------------- 35 36 2 - access("OBJECT_ID"=TO_NUMBER(:A)) 37 38Note 39----- 40 - dynamic sampling used for this statement (level=2) 41 4232 rows selected.
如果我们想让它走全表扫描，首先获取全表扫描HINT
1LHR@dlhr> explain plan for select /*+ full(TB_LHR_20160525) */* from TB_LHR_20160525 where object_id= :a; 2 3Explained. 4 5LHR@dlhr> select * from table(dbms_xplan.display(null,null,'outline')); 6 7PLAN_TABLE_OUTPUT 8----------------------------------------------------------------------------------------- 9Plan hash value: 3458810051011-------------------------------------------------------------------------------------12| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |13-------------------------------------------------------------------------------------14| 0 | SELECT STATEMENT | | 886 | 179K| 352 (2)| 00:00:05 |15|* 1 | TABLE ACCESS FULL| TB_LHR_20160525 | 886 | 179K| 352 (2)| 00:00:05 |16-------------------------------------------------------------------------------------1718Outline Data19-------------2021 /*+22 BEGIN_OUTLINE_DATA23 FULL(@"SEL$1" "TB_LHR_20160525"@"SEL$1")24 OUTLINE_LEAF(@"SEL$1")25 ALL_ROWS26 DB_VERSION('11.2.0.4')27 OPTIMIZER_FEATURES_ENABLE('11.2.0.4')28 IGNORE_OPTIM_EMBEDDED_HINTS29 END_OUTLINE_DATA30 */3132Predicate Information (identified by operation id):33---------------------------------------------------3435 1 - filter("OBJECT_ID"=TO_NUMBER(:A))3637Note38-----39 - dynamic sampling used for this statement (level=2)404131 rows selected.explain plan for select /*+ full(TB_LHR_20160525) */* from TB_LHR_20160525 where object_id= :a; 2 3Explained. 4 5LHR@dlhr> select * from table(dbms_xplan.display(null,null,'outline')); 6 7PLAN_TABLE_OUTPUT 8----------------------------------------------------------------------------------------- 9Plan hash value: 345881005 10 11------------------------------------------------------------------------------------- 12| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | 13------------------------------------------------------------------------------------- 14| 0 | SELECT STATEMENT | | 886 | 179K| 352 (2)| 00:00:05 | 15|* 1 | TABLE ACCESS FULL| TB_LHR_20160525 | 886 | 179K| 352 (2)| 00:00:05 | 16------------------------------------------------------------------------------------- 17 18Outline Data 19------------- 20 21 /*+ 22 BEGIN_OUTLINE_DATA 23 FULL(@"SEL$1" "TB_LHR_20160525"@"SEL$1") 24 OUTLINE_LEAF(@"SEL$1") 25 ALL_ROWS 26 DB_VERSION('11.2.0.4') 27 OPTIMIZER_FEATURES_ENABLE('11.2.0.4') 28 IGNORE_OPTIM_EMBEDDED_HINTS 29 END_OUTLINE_DATA 30 */ 31 32Predicate Information (identified by operation id): 33--------------------------------------------------- 34 35 1 - filter("OBJECT_ID"=TO_NUMBER(:A)) 36 37Note 38----- 39 - dynamic sampling used for this statement (level=2) 40 4131 rows selected.
可以看到全表扫描的Hint已经为我们生成了，我们选取必要的hint就OK了，其它的可以不要，使用SQL Profile
1LHR@dlhr> declare 2 2 v_hints sys.sqlprof_attr; 3 3 begin 4 4 v_hints := sys.sqlprof_attr('FULL(@"SEL$1" "TB_LHR_20160525"@"SEL$1")'); ----------从上面Outline Data部分获取到的HINT 5 5 dbms_sqltune.import_sql_profile('select * from TB_LHR_20160525 where object_id= :a', ----------SQL语句部分 6 6 v_hints, 7 7 'TB_LHR_20160525', --------PROFILE 的名字 8 8 force_match => true); 9 9 end;10 10 /1112PL/SQL procedure successfully completed.13declare 2 2 v_hints sys.sqlprof_attr; 3 3 begin 4 4 v_hints := sys.sqlprof_attr('FULL(@"SEL$1" "TB_LHR_20160525"@"SEL$1")'); ----------从上面Outline Data部分获取到的HINT 5 5 dbms_sqltune.import_sql_profile('select * from TB_LHR_20160525 where object_id= :a', ----------SQL语句部分 6 6 v_hints, 7 7 'TB_LHR_20160525', --------PROFILE 的名字 8 8 force_match => true); 9 9 end; 10 10 / 11 12PL/SQL procedure successfully completed. 13
查看是否生效，已经生效了：
1LHR@dlhr> explain plan for select * from TB_LHR_20160525 where object_id= :a; 2 3Explained. 4 5LHR@dlhr> select * from table(dbms_xplan.display); 6 7PLAN_TABLE_OUTPUT 8----------------------------------------------------------------------------------------------------------------------------Plan hash value: 345881005 910-------------------------------------------------------------------------------------11| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |12-------------------------------------------------------------------------------------13| 0 | SELECT STATEMENT | | 886 | 179K| 352 (2)| 00:00:05 |14|* 1 | TABLE ACCESS FULL| TB_LHR_20160525 | 886 | 179K| 352 (2)| 00:00:05 |15-------------------------------------------------------------------------------------1617Predicate Information (identified by operation id):18---------------------------------------------------1920 1 - filter("OBJECT_ID"=TO_NUMBER(:A))2122Note23-----24 - dynamic sampling used for this statement (level=2)25 - SQL profile "TB_LHR_20160525" used for this statement262718 rows selected.2829LHR@dlhr> SELECT b.name,d.sql_text, extractvalue(value(h),'.') as hints30 2 FROM dba_sql_profiles d,SYS.SQLOBJ$DATA A,31 3 SYS.SQLOBJ$ B,32 4 TABLE(XMLSEQUENCE(EXTRACT(XMLTYPE(A.COMP_DATA),33 5 '/outline_data/hint'))) h34 6 where a.signature = b.signature35 7 and a.category = b.category36 8 and a.obj_type = b.obj_type37 9 and a.plan_id = b.plan_id38 10 and a.signature=d.signature39 11 and D.name = 'TB_LHR_20160525'; 4041NAME SQL_TEXT HINTS42------------------------------ -------------------------------------------------------------------------------- -------------------------------------------------------43TB_LHR_20160525 select * from TB_LHR_20160525 where object_id= :a FULL(@"SEL$1" "TB_LHR_20160525"@"SEL$1")explain plan for select * from TB_LHR_20160525 where object_id= :a; 2 3Explained. 4 5LHR@dlhr> select * from table(dbms_xplan.display); 6 7PLAN_TABLE_OUTPUT 8----------------------------------------------------------------------------------------------------------------------------Plan hash value: 345881005 9 10------------------------------------------------------------------------------------- 11| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | 12------------------------------------------------------------------------------------- 13| 0 | SELECT STATEMENT | | 886 | 179K| 352 (2)| 00:00:05 | 14|* 1 | TABLE ACCESS FULL| TB_LHR_20160525 | 886 | 179K| 352 (2)| 00:00:05 | 15------------------------------------------------------------------------------------- 16 17Predicate Information (identified by operation id): 18--------------------------------------------------- 19 20 1 - filter("OBJECT_ID"=TO_NUMBER(:A)) 21 22Note 23----- 24 - dynamic sampling used for this statement (level=2) 25 - SQL profile "TB_LHR_20160525" used for this statement 26 2718 rows selected. 28 29LHR@dlhr> SELECT b.name,d.sql_text, extractvalue(value(h),'.') as hints 30 2 FROM dba_sql_profiles d,SYS.SQLOBJ$DATA A, 31 3 SYS.SQLOBJ$ B, 32 4 TABLE(XMLSEQUENCE(EXTRACT(XMLTYPE(A.COMP_DATA), 33 5 '/outline_data/hint'))) h 34 6 where a.signature = b.signature 35 7 and a.category = b.category 36 8 and a.obj_type = b.obj_type 37 9 and a.plan_id = b.plan_id 38 10 and a.signature=d.signature 39 11 and D.name = 'TB_LHR_20160525'; 40 41NAME SQL_TEXT HINTS 42------------------------------ -------------------------------------------------------------------------------- ------------------------------------------------------- 43TB_LHR_20160525 select * from TB_LHR_20160525 where object_id= :a FULL(@"SEL$1" "TB_LHR_20160525"@"SEL$1")
最麻烦的sqlprof_attr('FULL(t1@SEL$1)')是这里的格式如何写，在Mos上的文章note 215187.1中的sqlt.zip的目录utl中提供了脚本coe_xfr_sql_profile.sql可以生成这些信息。
本文选自《Oracle程序员面试笔试宝典》，作者：李华荣。
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