根据执行计划优化sql语句
2016-03-19 14:43
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优化前:表连接使用merge
将上面的执行计划中的merge改为hash连接,使用hint再次执行:
针对该sql,在创建新的profile。
SQL> alter session set statistics_level=all; Session altered. SQL> select e.sal,d.dname from (select deptno,sum(sal) sal from emp group by deptno) e,dept d where d.deptno=e.deptno; SAL DNAME ---------- -------------- 8750 ACCOUNTING 10875 RESEARCH 9400 SALES SQL> select * from table(dbms_xplan.display_cursor(null,null,'allstats +alias +outline')); PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- SQL_ID g2kzsydh3kmmq, child number 0 ------------------------------------- select e.sal,d.dname from (select deptno,sum(sal) sal from emp group by deptno) e,dept d where d.deptno=e.deptno Plan hash value: 2992795152 ----------------------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | OMem | 1Mem | O/1/M | ----------------------------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 2 | | 6 |00:00:00.01 | 20 | | | | | 1 | MERGE JOIN | | 2 | 3 | 6 |00:00:00.01 | 20 | | | | | 2 | TABLE ACCESS BY INDEX ROWID| DEPT | 2 | 4 | 8 |00:00:00.01 | 8 | | | | | 3 | INDEX FULL SCAN | PK_DEPT | 2 | 4 | 8 |00:00:00.01 | 4 | | | | |* 4 | SORT JOIN | | 8 | 3 | 6 |00:00:00.01 | 12 | 2048 | 2048 | 2/0/0| | 5 | VIEW | | 2 | 3 | 6 |00:00:00.01 | 12 | | | | | 6 | HASH GROUP BY | | 2 | 3 | 6 |00:00:00.01 | 12 | 1214K| 1214K| 2/0/0| | 7 | TABLE ACCESS FULL | EMP | 2 | 14 | 28 |00:00:00.01 | 12 | | | | ----------------------------------------------------------------------------------------------------------------------------- Query Block Name / Object Alias (identified by operation id): ------------------------------------------------------------- 1 - SEL$1 2 - SEL$1 / D@SEL$1 3 - SEL$1 / D@SEL$1 5 - SEL$2 / E@SEL$1 6 - SEL$2 7 - SEL$2 / EMP@SEL$2 Outline Data ------------- /*+ BEGIN_OUTLINE_DATA IGNORE_OPTIM_EMBEDDED_HINTS OPTIMIZER_FEATURES_ENABLE('11.2.0.4') DB_VERSION('11.2.0.4') ALL_ROWS OUTLINE_LEAF(@"SEL$2") OUTLINE_LEAF(@"SEL$1") INDEX(@"SEL$1" "D"@"SEL$1" ("DEPT"."DEPTNO")) NO_ACCESS(@"SEL$1" "E"@"SEL$1") LEADING(@"SEL$1" "D"@"SEL$1" "E"@"SEL$1") USE_MERGE(@"SEL$1" "E"@"SEL$1") FULL(@"SEL$2" "EMP"@"SEL$2") USE_HASH_AGGREGATION(@"SEL$2") END_OUTLINE_DATA */ Predicate Information (identified by operation id): --------------------------------------------------- 4 - access("D"."DEPTNO"="E"."DEPTNO") filter("D"."DEPTNO"="E"."DEPTNO") 56 rows selected. SQL>
将上面的执行计划中的merge改为hash连接,使用hint再次执行:
SQL> select /*+ 2 BEGIN_OUTLINE_DATA 3 IGNORE_OPTIM_EMBEDDED_HINTS 4 OPTIMIZER_FEATURES_ENABLE('11.2.0.4') 5 DB_VERSION('11.2.0.4') 6 ALL_ROWS 7 OUTLINE_LEAF(@"SEL$2") 8 OUTLINE_LEAF(@"SEL$1") 9 INDEX(@"SEL$1" "D"@"SEL$1" ("DEPT"."DEPTNO")) 10 NO_ACCESS(@"SEL$1" "E"@"SEL$1") 11 LEADING(@"SEL$1" "D"@"SEL$1" "E"@"SEL$1") 12 USE_HASH(@"SEL$1" "E"@"SEL$1") 13 FULL(@"SEL$2" "EMP"@"SEL$2") 14 USE_HASH_AGGREGATION(@"SEL$2") 15 END_OUTLINE_DATA 16 */ e.sal,d.dname from (select deptno,sum(sal) sal from emp group by deptno) e,dept d where d.deptno=e.deptno; SAL DNAME ---------- -------------- 9400 SALES 10875 RESEARCH 8750 ACCOUNTING SQL> select * from table(dbms_xplan.display_cursor(null,null,'allstats +alias +outline')); PLAN_TABLE_OUTPUT -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- SQL_ID 5sns096pbcwj8, child number 0 ------------------------------------- select /*+ BEGIN_OUTLINE_DATA IGNORE_OPTIM_EMBEDDED_HINTS OPTIMIZER_FEATURES_ENABLE('11.2.0.4') DB_VERSION('11.2.0.4') ALL_ROWS OUTLINE_LEAF(@"SEL$2") OUTLINE_LEAF(@"SEL$1") INDEX(@"SEL$1" "D"@"SEL$1" ("DEPT"."DEPTNO")) NO_ACCESS(@"SEL$1" "E"@"SEL$1") LEADING(@"SEL$1" "D"@"SEL$1" "E"@"SEL$1") USE_HASH(@"SEL$1" "E"@"SEL$1") FULL(@"SEL$2" "EMP"@"SEL$2") USE_HASH_AGGREGATION(@"SEL$2") END_OUTLINE_DATA */ e.sal,d.dname from (select deptno,sum(sal) sal from emp group by deptno) e,dept d where d.deptno=e.deptno Plan hash value: 208030399 ----------------------------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | OMem | 1Mem | O/1/M | ----------------------------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | | 3 |00:00:00.01 | 8 | | | | |* 1 | HASH JOIN | | 1 | 3 | 3 |00:00:00.01 | 8 | 1599K| 1599K| 1/0/0| | 2 | TABLE ACCESS BY INDEX ROWID| DEPT | 1 | 4 | 4 |00:00:00.01 | 2 | | | | | 3 | INDEX FULL SCAN | PK_DEPT | 1 | 4 | 4 |00:00:00.01 | 1 | | | | | 4 | VIEW | | 1 | 3 | 3 |00:00:00.01 | 6 | | | | | 5 | HASH GROUP BY | | 1 | 3 | 3 |00:00:00.01 | 6 | 1214K| 1214K| 1/0/0| | 6 | TABLE ACCESS FULL | EMP | 1 | 14 | 14 |00:00:00.01 | 6 | | | | ----------------------------------------------------------------------------------------------------------------------------- Query Block Name / Object Alias (identified by operation id): ------------------------------------------------------------- 1 - SEL$1 2 - SEL$1 / D@SEL$1 3 - SEL$1 / D@SEL$1 4 - SEL$2 / E@SEL$1 5 - SEL$2 6 - SEL$2 / EMP@SEL$2 Outline Data ------------- /*+ BEGIN_OUTLINE_DATA IGNORE_OPTIM_EMBEDDED_HINTS OPTIMIZER_FEATURES_ENABLE('11.2.0.4') DB_VERSION('11.2.0.4') ALL_ROWS OUTLINE_LEAF(@"SEL$2") OUTLINE_LEAF(@"SEL$1") INDEX(@"SEL$1" "D"@"SEL$1" ("DEPT"."DEPTNO")) NO_ACCESS(@"SEL$1" "E"@"SEL$1") LEADING(@"SEL$1" "D"@"SEL$1" "E"@"SEL$1") USE_HASH(@"SEL$1" "E"@"SEL$1") FULL(@"SEL$2" "EMP"@"SEL$2") USE_HASH_AGGREGATION(@"SEL$2") END_OUTLINE_DATA */ Predicate Information (identified by operation id): --------------------------------------------------- 1 - access("D"."DEPTNO"="E"."DEPTNO") 62 rows selected. SQL>
针对该sql,在创建新的profile。
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