ORACLE11G優化器對full Outer join 的加強
阿新 • • 發佈：2019-01-31
1 降級優化器到10.2SQL> alter system set optimizer_features_enable ='10.2.0.2' scope=memory ; System altered. 2 執行全外連線語句 SQL> set autotrace trace SQL> set pagesize 200 SQL> set linesize 200 SQL> select * 2 from ESTIMATES e 3 full outer join ACTUALS a on e.ITEM_NBR = a.ITEM_NBR ; 8 rows selected. Execution Plan ---------------------------------------------------------- Plan hash value: 2047377711 ---------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ---------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 7 | 406 | 13 (8)| 00:00:01 | | 1 | VIEW | | 7 | 406 | 13 (8)| 00:00:01 | | 2 | UNION-ALL | | | | | | |* 3 | HASH JOIN OUTER | | 6 | 108 | 7 (15)| 00:00:01 | | 4 | TABLE ACCESS FULL| ESTIMATES | 5 | 30 | 3 (0)| 00:00:01 | | 5 | TABLE ACCESS FULL| ACTUALS | 4 | 48 | 3 (0)| 00:00:01 | |* 6 | HASH JOIN ANTI | | 1 | 15 | 7 (15)| 00:00:01 | | 7 | TABLE ACCESS FULL| ACTUALS | 4 | 48 | 3 (0)| 00:00:01 | | 8 | TABLE ACCESS FULL| ESTIMATES | 5 | 15 | 3 (0)| 00:00:01 | ---------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 3 - access("E"."ITEM_NBR"="A"."ITEM_NBR"(+)) 6 - access("E"."ITEM_NBR"="A"."ITEM_NBR") Statistics ---------------------------------------------------------- 33 recursive calls 4 db block gets 53 consistent gets 1 physical reads 0 redo size 988 bytes sent via SQL*Net to client 523 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 8 sorts (memory) 0 sorts (disk) 8 rows processed
3 執行根據執行計劃反寫的SQL語句SQL> select * 2 from ESTIMATES e, ACTUALS a 3 where e.ITEM_NBR = a.ITEM_NBR(+) 4 union all 5 select null, null, a.* 6 from ACTUALS a 7 where not exists (select 1 from ESTIMATES e where e.item_nbr = a.item_nbr); 8 rows selected. Execution Plan ---------------------------------------------------------- Plan hash value: 3616513639 --------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 7 | 123 | 13 (54)| 00:00:01 | | 1 | UNION-ALL | | | | | | |* 2 | HASH JOIN OUTER | | 6 | 108 | 7 (15)| 00:00:01 | | 3 | TABLE ACCESS FULL| ESTIMATES | 5 | 30 | 3 (0)| 00:00:01 | | 4 | TABLE ACCESS FULL| ACTUALS | 4 | 48 | 3 (0)| 00:00:01 | |* 5 | HASH JOIN ANTI | | 1 | 15 | 7 (15)| 00:00:01 | | 6 | TABLE ACCESS FULL| ACTUALS | 4 | 48 | 3 (0)| 00:00:01 | | 7 | TABLE ACCESS FULL| ESTIMATES | 5 | 15 | 3 (0)| 00:00:01 | --------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("E"."ITEM_NBR"="A"."ITEM_NBR"(+)) 5 - access("E"."ITEM_NBR"="A"."ITEM_NBR") Statistics ---------------------------------------------------------- 1 recursive calls 0 db block gets 25 consistent gets 0 physical reads 0 redo size 988 bytes sent via SQL*Net to client 523 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 8 rows processed 4 將優化器升級到11.2.0.2 SQL> alter system set optimizer_features_enable ='11.2.0.2' scope=memory ; System altered. 5 再次執行全外連線語句 SQL> select * 2 from ESTIMATES e 3 full outer join ACTUALS a on e.ITEM_NBR = a.ITEM_NBR ; 8 rows selected. Execution Plan ---------------------------------------------------------- Plan hash value: 1818351901 ----------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ----------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 6 | 348 | 7 (15)| 00:00:01 | | 1 | VIEW | VW_FOJ_0 | 6 | 348 | 7 (15)| 00:00:01 | |* 2 | HASH JOIN FULL OUTER| | 6 | 108 | 7 (15)| 00:00:01 | | 3 | TABLE ACCESS FULL | ACTUALS | 4 | 48 | 3 (0)| 00:00:01 | | 4 | TABLE ACCESS FULL | ESTIMATES | 5 | 30 | 3 (0)| 00:00:01 | ----------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - access("E"."ITEM_NBR"="A"."ITEM_NBR") Statistics ---------------------------------------------------------- 1 recursive calls 0 db block gets 13 consistent gets 0 physical reads 0 redo size 997 bytes sent via SQL*Net to client 523 bytes received via SQL*Net from client 2 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 8 rows processed
總結：11g優化器對全外連線進行了加強，降低了執行計劃複雜程度與索要消耗的資源。