Question

SELECT * FROM v $ version;

Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - Production  
PL/SQL Release 11.2.0.4.0 - Production  
"CORE 11.2.0.4.0 Production"  
TNS for Linux: Version 11.2.0.4.0 - Production  
NLSRTL Version 11.2.0.4.0 - Production

有以下用例： -

--Create Table T1
create table t1 as select * from all_objects where 1=0;

--Create Table T2
create table t2 as select * from all_objects where 1=0;

--Gather stats on T1
exec dbms_stats.set_table_stats( user, 'T1', numrows=>10000000, numblks=> 1000000 );

--Gather stats on T1
exec dbms_stats.set_table_stats( user, 'T2', numrows=>10000000, numblks=> 1000000 );

--Enable autotrace
set autotrace traceonly explain

--Run SQL
with data
as
(select  * from t2 where object_id between 1 and 100000 )
select *
  from t2
 where not exists (select 1 from data where data.object_id = t2.object_id)
/

Execution Plan
----------------------------------------------------------
Plan hash value: 2779716391

---------------------------------------------------------------------------------------------------------
| Id  | Operation                  | Name                       | Rows  | Bytes | Cost(%CPU)| Time     |
---------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT           |                            |  9200K|   991M|   618K (2)| 00:48:59 |
|   1 |  TEMP TABLE TRANSFORMATION |                            |       |       |           |          |
|   2 |   LOAD AS SELECT           | T2                         |       |       |       |          |
|*  3 |    TABLE ACCESS FULL       | T2                         |  25000|  2441K|   308K (2)| 00:24:28 |
|*  4 |   HASH JOIN RIGHT ANTI     |                            |  9200K|   991M|   309K (2)| 00:24:32 |
|   5 |    VIEW                    |                            |  25000|   317K|   110  (4)| 00:00:01 |
|   6 |     TABLE ACCESS FULL      | SYS_TEMP_0FD9D6620_1BF817E |  25000|  2441K|   110  (4)| 00:00:01 |
|   7 |    TABLE ACCESS FULL       | T2                         |    10M|   953M|   309K (2)| 00:24:30 |
---------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

3 - filter("OBJECT_ID">=1 AND "OBJECT_ID"<=100000)
4 - access("DATA"."OBJECT_ID"="T2"."OBJECT_ID")

--Disable autotrace
set autotrace off

我的问题是 - 我可以以某种方式让优化器在创建的TEMP表上使用索引扫描'SYS_TEMP_0FD9D6620_1BF817E'??

以上是用于说明目的的示例，以提出我的问题。在实际情况中，我遇到的情况是，我创建的SYS_ *表（确切地说是3个）具有巨大的数据集（~5 +百万），并且FULL表扫描耗费了我的查询响应时间。

有没有办法通过无证提示更改（例如??），我可以加快对从WITH suquery中创建的SYS_ *表的访问速度吗？

非常感谢回应。

蒂亚..

Answer 1

要使用索引扫描，您必须先创建它。如果您想加快查询速度，请在没有WITH数据AS的情况下重写它，因为WITH需要大量的Oracle资源。以下是：

select *
  from t2
 where not exists (select 1
                     from t2
                    where object_id between 1 and 100000 
                      and object_id = t2.object_id);

加速在WITH子查询期间创建的SYS_ *表访问

1 个答案: