Oracle内联视图优化，视图合并的抉择_动视

Oracle内联视图优化，视图合并的抉择

2020-11-09 07:24:55 责编:小采

===================================================== Oracle 内联视图优化，视图合并的抉择内联视图in-line view，就是sql中from后面有select子查询，或者sql中包含有用create view创建的视图，CBO可能会将内联视图或者视图展开，进行相应的等价改写，这

=====================================================

Oracle 内联视图优化，视图合并的抉择

内联视图in-line view，就是sql中from后面有select子查询，或者sql中包含有用create view创建的视图，CBO可能会将内联视图或者视图展开，进行相应的等价改写，这种就叫视图合并。直接看一个sql的执行计划

1. user_tables和dba_objects都是静态数据字典，我们来看下sql的执行计划

SELECT to_char(wmsys.wm_concat(a.TABLE_NAME)) FROM user_tables a, dba_objects b WHERE a.TABLE_NAME = b.OBJECT_NAME AND b.OWNER = 'SCOTT' AND B.OBJECT_TYPE = 'TABLE'; 执行计划 ---------------------------------------------------------- Plan hash value: 555706832 ------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 190 | 1750 (1)| 00:00:22 | | 1 | SORT AGGREGATE | | 1 | 190 | | | |* 2 | HASH JOIN RIGHT OUTER | | 2425 | 449K| 1750 (1)| 00:00:22 | | 3 | TABLE ACCESS FULL | SEG$ | 5832 | 152 | 38 (0)| 00:00:01 | |* 4 | HASH JOIN RIGHT OUTER | | 2385 | 416K| 1711 (1)| 00:00:21 | | 5 | INDEX FULL SCAN | I_USER2 | 93 | 372 | 1 (0)| 00:00:01 | |* 6 | HASH JOIN OUTER | | 2385 | 407K| 1710 (1)| 00:00:21 | |* 7 | HASH JOIN OUTER | | 2385 | 388K| 1662 (1)| 00:00:20 | |* 8 | HASH JOIN | | 2385 | 377K| 1614 (1)| 00:00:20 | | 9 | TABLE ACCESS FULL | TS$ | 7 | 21 | 3 (0)| 00:00:01 | | 10 | NESTED LOOPS | | 2385 | 370K| 1611 (1)| 00:00:20 | |* 11 | HASH JOIN | | 2385 | 300K| 1517 (1)| 00:00:19 | | 12 | VIEW | DBA_OBJECTS | 2359 | 575 | 1313 (1)| 00:00:16 | | 13 | UNION-ALL | | | | | | |* 14 | TABLE ACCESS BY INDEX ROWID | SUM$ | 1 | 9 | 1 (0)| 00:00:01 | |* 15 | INDEX UNIQUE SCAN | I_SUM$_1 | 1 | | 0 (0)| 00:00:01 | |* 16 | FILTER | | | | | | |* 17 | HASH JOIN | | 25 | 3050 | 48 (3)| 00:00:01 | | 18 | NESTED LOOPS | | 25 | 2500 | 46 (0)| 00:00:01 | | 19 | TABLE ACCESS BY INDEX ROWID| USER$ | 1 | 17 | 1 (0)| 00:00:01 | |* 20 | INDEX UNIQUE SCAN | I_USER1 | 1 | | 0 (0)| 00:00:01 | |* 21 | TABLE ACCESS BY INDEX ROWID| OBJ$ | 25 | 2075 | 45 (0)| 00:00:01 | |* 22 | INDEX RANGE SCAN | I_OBJ5 | 25 | | 27 (0)| 00:00:01 | | 23 | INDEX FULL SCAN | I_USER2 | 93 | 2046 | 1 (0)| 00:00:01 | |* 24 | TABLE ACCESS BY INDEX ROWID | IND$ | 1 | 8 | 2 (0)| 00:00:01 | |* 25 | INDEX UNIQUE SCAN | I_IND1 | 1 | | 1 (0)| 00:00:01 | | 26 | NESTED LOOPS | | 1 | 29 | 2 (0)| 00:00:01 | |* 27 | INDEX FULL SCAN | I_USER2 | 1 | 20 | 1 (0)| 00:00:01 | |* 28 | INDEX RANGE SCAN | I_OBJ4 | 1 | 9 | 1 (0)| 00:00:01 | |* 29 | FILTER | | | | | | | 30 | NESTED LOOPS | | 1 | 96 | 1 (0)| 00:00:01 | | 31 | TABLE ACCESS BY INDEX ROWID | USER$ | 1 | 17 | 1 (0)| 00:00:01 | |* 32 | INDEX UNIQUE SCAN | I_USER1 | 1 | | 0 (0)| 00:00:01 | |* 33 | INDEX RANGE SCAN | I_LINK1 | 1 | 79 | 0 (0)| 00:00:01 | | 34 | MERGE JOIN CARTESIAN | | 2530 | 256K| 203 (2)| 00:00:03 | |* 35 | HASH JOIN | | 1 | 68 | 1 (100)| 00:00:01 | |* 36 | FIXED TABLE FULL | X$KSPPI | 1 | 55 | 0 (0)| 00:00:01 | | 37 | FIXED TABLE FULL | X$KSPPCV | 100 | 1300 | 0 (0)| 00:00:01 | | 38 | BUFFER SORT | | 2530 | 91080 | 203 (2)| 00:00:03 | |* 39 | TABLE ACCESS FULL | OBJ$ | 2530 | 91080 | 203 (2)| 00:00:03 | |* 40 | TABLE ACCESS CLUSTER | TAB$ | 1 | 30 | 1 (0)| 00:00:01 | |* 41 | INDEX UNIQUE SCAN | I_OBJ# | 1 | | 0 (0)| 00:00:01 | | 42 | INDEX FAST FULL SCAN | I_OBJ1 | 73384 | 358K| 47 (0)| 00:00:01 | | 43 | INDEX FAST FULL SCAN | I_OBJ1 | 73384 | 573K| 47 (0)| 00:00:01 | -------------------------------------------------------------------------------------------------------

SELECTto_char(wmsys.wm_concat(a.TABLE_NAME))

FROMuser_tablesa,dba_objectsb

WHEREa.TABLE_NAME=b.OBJECT_NAME

ANDb.OWNER='SCOTT'

ANDB.OBJECT_TYPE='TABLE';

执行计划

----------------------------------------------------------

Planhashvalue:555706832

-------------------------------------------------------------------------------------------------------

-------------------------------------------------------------------------------------------------------

| 0|SELECTSTATEMENT | | 1| 190| 1750 (1)|00:00:22|

| 1| SORTAGGREGATE | | 1| 190| | |

|* 2| HASHJOINRIGHTOUTER | | 2425| 449K| 1750 (1)|00:00:22|

| 3| TABLEACCESSFULL |SEG$ | 5832|152| 38 (0)|00:00:01|

|* 4| HASHJOINRIGHTOUTER | | 2385| 416K| 1711 (1)|00:00:21|

| 5| INDEXFULLSCAN |I_USER2 | 93| 372| 1 (0)|00:00:01|

|* 6| HASHJOINOUTER | | 2385| 407K| 1710 (1)|00:00:21|

|* 7| HASHJOINOUTER | | 2385| 388K| 1662 (1)|00:00:20|

|* 8| HASHJOIN | | 2385| 377K| 1614 (1)|00:00:20|

| 9| TABLEACCESSFULL |TS$ | 7| 21| 3 (0)|00:00:01|

| 10| NESTEDLOOPS | | 2385| 370K| 1611 (1)|00:00:20|

|*11| HASHJOIN | | 2385| 300K| 1517 (1)|00:00:19|

| 12| VIEW |DBA_OBJECTS| 2359|575| 1313 (1)|00:00:16|

| 13| UNION-ALL | | | | | |

|*14| TABLEACCESSBYINDEXROWID |SUM$ | 1| 9| 1 (0)|00:00:01|

|*15| INDEXUNIQUESCAN |I_SUM$_1 | 1| | 0 (0)|00:00:01|

|*16| FILTER | | | | | |

|*17| HASHJOIN | | 25| 3050| 48 (3)|00:00:01|

| 18| NESTEDLOOPS | | 25| 2500| 46 (0)|00:00:01|

| 19| TABLEACCESSBYINDEXROWID|USER$ | 1| 17| 1 (0)|00:00:01|

|*20| INDEXUNIQUESCAN |I_USER1 | 1| | 0 (0)|00:00:01|

|*21| TABLEACCESSBYINDEXROWID|OBJ$ | 25| 2075| 45 (0)|00:00:01|

|*22| INDEXRANGESCAN |I_OBJ5 | 25| | 27 (0)|00:00:01|

| 23| INDEXFULLSCAN |I_USER2 | 93| 2046| 1 (0)|00:00:01|

|*24| TABLEACCESSBYINDEXROWID |IND$ | 1| 8| 2 (0)|00:00:01|

|*25| INDEXUNIQUESCAN |I_IND1 | 1| | 1 (0)|00:00:01|

| 26| NESTEDLOOPS | | 1| 29| 2 (0)|00:00:01|

|*27| INDEXFULLSCAN |I_USER2 | 1| 20| 1 (0)|00:00:01|

|*28| INDEXRANGESCAN |I_OBJ4 | 1| 9| 1 (0)|00:00:01|

|*29| FILTER | | | | | |

| 30| NESTEDLOOPS | | 1| 96| 1 (0)|00:00:01|

| 31| TABLEACCESSBYINDEXROWID|USER$ | 1| 17| 1 (0)|00:00:01|

|*32| INDEXUNIQUESCAN |I_USER1 | 1| | 0 (0)|00:00:01|

|*33| INDEXRANGESCAN |I_LINK1 | 1| 79| 0 (0)|00:00:01|

| 34| MERGEJOINCARTESIAN | | 2530| 256K| 203 (2)|00:00:03|

|*35| HASHJOIN | | 1| 68| 1(100)|00:00:01|

|*36| FIXEDTABLEFULL |X$KSPPI | 1| 55| 0 (0)|00:00:01|

| 37| FIXEDTABLEFULL |X$KSPPCV | 100| 1300| 0 (0)|00:00:01|

| 38| BUFFERSORT | | 2530|91080| 203 (2)|00:00:03|

|*39| TABLEACCESSFULL |OBJ$ | 2530|91080| 203 (2)|00:00:03|

|*40| TABLEACCESSCLUSTER |TAB$ | 1| 30| 1 (0)|00:00:01|

|*41| INDEXUNIQUESCAN |I_OBJ# | 1| | 0 (0)|00:00:01|

| 42| INDEXFASTFULLSCAN |I_OBJ1 |73384| 358K| 47 (0)|00:00:01|

| 43| INDEXFASTFULLSCAN |I_OBJ1 |73384| 573K| 47 (0)|00:00:01|

-------------------------------------------------------------------------------------------------------

可以看到id=12这一步有一个view关键字，这一步正好是提取dba_objects视图的数据，然后此表和id=34这一步进行hash join，但hash join的表并不是sql当中的user_tables，而且在整个执行计划当中都找不到这个视图的信息，此视图被展开了。但这种情况我们是不需要展开的

2. 既然不需要展开，我们直接使用hint禁止视图合并

SQL> SELECT /*+ no_merge(a) */ to_char(wmsys.wm_concat(a.TABLE_NAME)) 2 FROM user_tables a, dba_objects b 3 WHERE a.TABLE_NAME = b.OBJECT_NAME 4 AND b.OWNER = 'SCOTT' 5 AND B.OBJECT_TYPE = 'TABLE'; 执行计划 ---------------------------------------------------------- Plan hash value: 3412902540 -------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | -------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 50 | 1756 (1)| 00:00:22 | | 1 | SORT AGGREGATE | | 1 | 50 | | | |* 2 | HASH JOIN | | 2359 | 115K| 1756 (1)| 00:00:22 | | 3 | VIEW | DBA_OBJECTS | 2359 | 575 | 1313 (1)| 00:00:16 | | 4 | UNION-ALL | | | | | | |* 5 | TABLE ACCESS BY INDEX ROWID | SUM$ | 1 | 9 | 1 (0)| 00:00:01 | |* 6 | INDEX UNIQUE SCAN | I_SUM$_1 | 1 | | 0 (0)| 00:00:01 | |* 7 | FILTER | | | | | | |* 8 | HASH JOIN | | 25 | 3050 | 48 (3)| 00:00:01 | | 9 | NESTED LOOPS | | 25 | 2500 | 46 (0)| 00:00:01 | | 10 | TABLE ACCESS BY INDEX ROWID| USER$ | 1 | 17 | 1 (0)| 00:00:01 | |* 11 | INDEX UNIQUE SCAN | I_USER1 | 1 | | 0 (0)| 00:00:01 | |* 12 | TABLE ACCESS BY INDEX ROWID| OBJ$ | 25 | 2075 | 45 (0)| 00:00:01 | |* 13 | INDEX RANGE SCAN | I_OBJ5 | 25 | | 27 (0)| 00:00:01 | | 14 | INDEX FULL SCAN | I_USER2 | 93 | 2046 | 1 (0)| 00:00:01 | |* 15 | TABLE ACCESS BY INDEX ROWID | IND$ | 1 | 8 | 2 (0)| 00:00:01 | |* 16 | INDEX UNIQUE SCAN | I_IND1 | 1 | | 1 (0)| 00:00:01 | | 17 | NESTED LOOPS | | 1 | 29 | 2 (0)| 00:00:01 | |* 18 | INDEX FULL SCAN | I_USER2 | 1 | 20 | 1 (0)| 00:00:01 | |* 19 | INDEX RANGE SCAN | I_OBJ4 | 1 | 9 | 1 (0)| 00:00:01 | |* 20 | FILTER | | | | | | | 21 | NESTED LOOPS | | 1 | 96 | 1 (0)| 00:00:01 | | 22 | TABLE ACCESS BY INDEX ROWID | USER$ | 1 | 17 | 1 (0)| 00:00:01 | |* 23 | INDEX UNIQUE SCAN | I_USER1 | 1 | | 0 (0)| 00:00:01 | |* 24 | INDEX RANGE SCAN | I_LINK1 | 1 | 79 | 0 (0)| 00:00:01 | | 25 | VIEW | USER_TABLES | 2573 | 325 | 442 (2)| 00:00:06 | |* 26 | HASH JOIN RIGHT OUTER | | 2573 | 414K| 442 (2)| 00:00:06 | | 27 | TABLE ACCESS FULL | SEG$ | 5832 | 152 | 38 (0)| 00:00:01 | |* 28 | HASH JOIN RIGHT OUTER | | 2530 | 380K| 403 (2)| 00:00:05 | | 29 | INDEX FULL SCAN | I_USER2 | 93 | 372 | 1 (0)| 00:00:01 | |* 30 | HASH JOIN OUTER | | 2530 | 370K| 402 (2)| 00:00:05 | |* 31 | HASH JOIN OUTER | | 2530 | 350K| 354 (2)| 00:00:05 | |* 32 | HASH JOIN | | 2530 | 338K| 306 (2)| 00:00:04 | | 33 | TABLE ACCESS FULL | TS$ | 7 | 21 | 3 (0)| 00:00:01 | | 34 | NESTED LOOPS | | 2530 | 331K| 302 (1)| 00:00:04 | | 35 | MERGE JOIN CARTESIAN | | 2530 | 256K| 203 (2)| 00:00:03 | |* 36 | HASH JOIN | | 1 | 68 | 1 (100)| 00:00:01 | |* 37 | FIXED TABLE FULL | X$KSPPI | 1 | 55 | 0 (0)| 00:00:01 | | 38 | FIXED TABLE FULL | X$KSPPCV | 100 | 1300 | 0 (0)| 00:00:01 | | 39 | BUFFER SORT | | 2530 | 91080 | 203 (2)| 00:00:03 | |* 40 | TABLE ACCESS FULL | OBJ$ | 2530 | 91080 | 203 (2)| 00:00:03 | |* 41 | TABLE ACCESS CLUSTER | TAB$ | 1 | 30 | 1 (0)| 00:00:01 | |* 42 | INDEX UNIQUE SCAN | I_OBJ# | 1 | | 0 (0)| 00:00:01 | | 43 | INDEX FAST FULL SCAN | I_OBJ1 | 73384 | 358K| 47 (0)| 00:00:01 | | 44 | INDEX FAST FULL SCAN | I_OBJ1 | 73384 | 573K| 47 (0)| 00:00:01 | --------------------------------------------------------------------------------------------------

SQL>SELECT/*+ no_merge(a) */to_char(wmsys.wm_concat(a.TABLE_NAME))

2 FROMuser_tablesa,dba_objectsb

3 WHEREa.TABLE_NAME=b.OBJECT_NAME

4 ANDb.OWNER='SCOTT'

5 ANDB.OBJECT_TYPE ='TABLE';

执行计划

----------------------------------------------------------

Planhashvalue:3412902540

--------------------------------------------------------------------------------------------------

--------------------------------------------------------------------------------------------------

| 0|SELECTSTATEMENT | | 1| 50| 1756 (1)|00:00:22|

| 1| SORTAGGREGATE | | 1| 50| | |

|* 2| HASHJOIN | | 2359| 115K| 1756 (1)|00:00:22|

| 3| VIEW |DBA_OBJECTS| 2359|575| 1313 (1)|00:00:16|

| 4| UNION-ALL | | | | | |

|* 5| TABLEACCESSBYINDEXROWID |SUM$ | 1| 9| 1 (0)|00:00:01|

|* 6| INDEXUNIQUESCAN |I_SUM$_1 | 1| | 0 (0)|00:00:01|

|* 7| FILTER | | | | | |

|* 8| HASHJOIN | | 25| 3050| 48 (3)|00:00:01|

| 9| NESTEDLOOPS | | 25| 2500| 46 (0)|00:00:01|

| 10| TABLEACCESSBYINDEXROWID|USER$ | 1| 17| 1 (0)|00:00:01|

|*11| INDEXUNIQUESCAN |I_USER1 | 1| | 0 (0)|00:00:01|

|*12| TABLEACCESSBYINDEXROWID|OBJ$ | 25| 2075| 45 (0)|00:00:01|

|*13| INDEXRANGESCAN |I_OBJ5 | 25| | 27 (0)|00:00:01|

| 14| INDEXFULLSCAN |I_USER2 | 93| 2046| 1 (0)|00:00:01|

|*15| TABLEACCESSBYINDEXROWID |IND$ | 1| 8| 2 (0)|00:00:01|

|*16| INDEXUNIQUESCAN |I_IND1 | 1| | 1 (0)|00:00:01|

| 17| NESTEDLOOPS | | 1| 29| 2 (0)|00:00:01|

|*18| INDEXFULLSCAN |I_USER2 | 1| 20| 1 (0)|00:00:01|

|*19| INDEXRANGESCAN |I_OBJ4 | 1| 9| 1 (0)|00:00:01|

|*20| FILTER | | | | | |

| 21| NESTEDLOOPS | | 1| 96| 1 (0)|00:00:01|

| 22| TABLEACCESSBYINDEXROWID|USER$ | 1| 17| 1 (0)|00:00:01|

|*23| INDEXUNIQUESCAN |I_USER1 | 1| | 0 (0)|00:00:01|

|*24| INDEXRANGESCAN |I_LINK1 | 1| 79| 0 (0)|00:00:01|

| 25| VIEW |USER_TABLES| 2573|325| 442 (2)|00:00:06|

|*26| HASHJOINRIGHTOUTER | | 2573| 414K| 442 (2)|00:00:06|

| 27| TABLEACCESSFULL |SEG$ | 5832|152| 38 (0)|00:00:01|

|*28| HASHJOINRIGHTOUTER | | 2530| 380K| 403 (2)|00:00:05|

| 29| INDEXFULLSCAN |I_USER2 | 93| 372| 1 (0)|00:00:01|

|*30| HASHJOINOUTER | | 2530| 370K| 402 (2)|00:00:05|

|*31| HASHJOINOUTER | | 2530| 350K| 354 (2)|00:00:05|

|*32| HASHJOIN | | 2530| 338K| 306 (2)|00:00:04|

| 33| TABLEACCESSFULL |TS$ | 7| 21| 3 (0)|00:00:01|

| 34| NESTEDLOOPS | | 2530| 331K| 302 (1)|00:00:04|

| 35| MERGEJOINCARTESIAN | | 2530| 256K| 203 (2)|00:00:03|

|*36| HASHJOIN | | 1| 68| 1(100)|00:00:01|

|*37| FIXEDTABLEFULL |X$KSPPI | 1| 55| 0 (0)|00:00:01|

| 38| FIXEDTABLEFULL |X$KSPPCV | 100| 1300| 0 (0)|00:00:01|

| 39| BUFFERSORT | | 2530|91080| 203 (2)|00:00:03|

|*40| TABLEACCESSFULL |OBJ$ | 2530|91080| 203 (2)|00:00:03|

|*41| TABLEACCESSCLUSTER |TAB$ | 1| 30| 1 (0)|00:00:01|

|*42| INDEXUNIQUESCAN |I_OBJ# | 1| | 0 (0)|00:00:01|

| 43| INDEXFASTFULLSCAN |I_OBJ1 |73384| 358K| 47 (0)|00:00:01|

| 44| INDEXFASTFULLSCAN |I_OBJ1 |73384| 573K| 47 (0)|00:00:01|

--------------------------------------------------------------------------------------------------

现在可以在执行计划中看到id=3和id=25这两步都是视图，通过hash join连接。

疑问：为什么这里不需要视图合并？

答曰：如果不视图合并，那整个视图就会当成一整块，在sql执行的时候，这个视图就是一个结果集，然后再去和另一个结果集关联。如果合并了的话，那这个视图就会被拆散，视图里面的关联就会分开run，并不是每次视图合并都是高效的。

在执行计划中，如果看到view关键字，说明视图没有展开，也就是视图没有合并，如果本来sql中有内联视图或者视图，但执行计划中没有看到view关键字，那这个sql就进行了视图合并。

此外还需要注意的是，如果sql中的内联视图有聚合等操作，比如rownum，start with，connect by，union，union all，rollup，cube等，这种内联视图就不能展开，因为内联视图被固化了，碰到这种情况就需要注意，如果内联视图中结果集很大，那sql估计就要改写了，因为这个内联视图会最先执行。

http://www.savedba.com/?p=816

============================================

3.1.1.1　内联视图合并

2013-02-25 16:45 黄玮机械工业出版社我要评论(0) 字号：T | T

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《Oracle高性能SQL引擎剖析：SQL优化与调优机制详解》第3章查询转换，在本章中，我们将会了解到以下内容：Oracle的逻辑优化技术中，存在哪些启发式查询转换技术，以及它们的具体含义和示例；Oracle的逻辑优化技术中，存在哪些基于代价的查询转换技术，以及它们的具体含义和示例。本节为大家介绍内联视图合并。

AD：2014WOT全球软件技术峰会北京站课程视频发布

3.1.1.1　内联视图合并

我们以下面两个执行计划为例，简要说明视图合并技术对执行计划优化的影响，见代码清单3-1。

代码清单3-1　内联视图合并

HELLODBA.COM>exec sql_explain('select /*+no_merge(o)*/* from t_tables t, v_objects_sys o where 
 t.owner=o.owner and t.table_name = object_name and t.tablespace_name = :A and t.table_name 
 like :B and o.status=:C', 'TYPICAL'); 
Plan hash value: 3284354748 
---------------------------------------------------------------------------------------------------- 
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | 
---------------------------------------------------------------------------------------------------- 
| 0 | SELECT STATEMENT | | 3 | 840 | 87 (3)| 00:00:01 | 
|* 1 | HASH JOIN | | 3 | 840 | 87 (3)| 00:00:01 | 
| 2 | TABLE ACCESS BY INDEX ROWID | T_TABLES | 9 | 1836 | 13 (8)| 00:00:01 | 
| 3 | BITMAP CONVERSION TO ROWIDS | | | | | | 
| 4 | BITMAP AND | | | | | | 
| 5 | BITMAP CONVERSION FROM ROWIDS| | | | | | 
|* 6 | INDEX RANGE SCAN | T_TABLES_IDX3 | 184 | | 1 (0)| 00:00:01 | 
| 7 | BITMAP CONVERSION FROM ROWIDS| | | | | | 
| 8 | SORT ORDER BY | | | | | | 
|* 9 | INDEX RANGE SCAN | T_TABLES_PK | 184 | | 2 (0)| 00:00:01 | 
| 10 | VIEW | V_OBJECTS_SYS | 571 | 43396 | 73 (0)| 00:00:01 | 
| 11 | TABLE ACCESS BY INDEX ROWID | T_OBJECTS | 571 | 47393 | 73 (0)| 00:00:01 | 
|* 12 | INDEX RANGE SCAN | T_OBJECTS_IDX1 | 103 | | 3 (0)| 00:00:01 | 
---------------------------------------------------------------------------------------------------- 
 
Predicate Information (identified by operation id): 
--------------------------------------------------- 
 1 - access("T"."OWNER&quo 




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Oracle 内联视图优化，视图合并的抉择

3.1.1.1 内联视图合并

3.1.1.1　内联视图合并