【Oracle】如何在查询视图时使用索引

通常我们使用hint来固定查询计划选择走表的索引固定表的连接等等，但是如果第一层查询的是视图呢？

yang@rac1>CREATE TABLE TA (ID NUMBER, NAME VARCHAR2(30), TYPE VARCHAR2(30));Table created.yang@rac1>CREATE TABLE TB (ID NUMBER, NAME VARCHAR2(30), TYPE VARCHAR2(30));Table created.yang@rac1>create index idx_id_ta on ta(id);Index created.yang@rac1>create index idx_id_tb on tb(id);Index created.yang@rac1>CREATE VIEW V_Tab AS2   SELECT * FROM TA3  UNION ALL4    SELECT * FROM TB;View created.

普通的查询视图，并没有走索引。

yang@rac1> SELECT  * 2     FROM V_TAB3     WHERE ID<2500;9996 rows selected.Execution Plan----------------------------------------------------------Plan hash value: 4036260501-----------------------------------------------------------------------------| Id  | Operation           | Name  | Rows  | Bytes | Cost (%CPU)| Time     |-----------------------------------------------------------------------------|   0 | SELECT STATEMENT    |       |     1 |    47 |     2   (0)| 00:00:01 ||   1 |  VIEW               | V_TAB |     1 |    47 |     2   (0)| 00:00:01 ||   2 |   UNION-ALL         |       |       |       |            |          ||*  3 |    TABLE ACCESS FULL| TA    |  4998 |   229K|     9   (0)| 00:00:01 ||*  4 |    TABLE ACCESS FULL| TB    |  4998 |   229K|     9   (0)| 00:00:01 |-----------------------------------------------------------------------------Predicate Information (identified by operation id):---------------------------------------------------3 - filter("ID"<2500)4 - filter("ID"<2500)Note------ dynamic sampling used for this statement (level=2)

====使用常规使用hint的方式(表名索引名称)

yang@rac1> SELECT /*+ index(tb  idx_id_tb) index(ta idx_id_ta) */* 2     FROM V_TAB3     WHERE ID<2500;9996 rows selected.Execution Plan----------------------------------------------------------Plan hash value: 4036260501-----------------------------------------------------------------------------| Id  | Operation           | Name  | Rows  | Bytes | Cost (%CPU)| Time     |-----------------------------------------------------------------------------|   0 | SELECT STATEMENT    |       |     1 |    47 |     2   (0)| 00:00:01 ||   1 |  VIEW               | V_TAB |     1 |    47 |     2   (0)| 00:00:01 ||   2 |   UNION-ALL         |       |       |       |            |          ||*  3 |    TABLE ACCESS FULL| TA    |  4998 |   229K|     9   (0)| 00:00:01 ||*  4 |    TABLE ACCESS FULL| TB    |  4998 |   229K|     9   (0)| 00:00:01 |-----------------------------------------------------------------------------Predicate Information (identified by operation id):---------------------------------------------------3 - filter("ID"<2500)4 - filter("ID"<2500)

并不凑效！依然走全表扫描！

Note

-----

- dynamic sampling used for this statement (level=2)

==使用视图前缀修饰表名的方式(VIVE.TABNAME INDEX_NAME)

yang@rac1> SELECT /*+ index(v_tab.tb  idx_id_tb) index(v_tab.ta idx_id_ta) */* 2     FROM V_TAB3     WHERE ID<2500;9996 rows selected.Execution Plan----------------------------------------------------------Plan hash value: 531820221-------------------------------------------------------------------------------------------| Id  | Operation                     | Name      | Rows  | Bytes | Cost (%CPU)| Time     |-------------------------------------------------------------------------------------------|   0 | SELECT STATEMENT              |           |     1 |    47 |     2   (0)| 00:00:01 ||   1 |  VIEW                         | V_TAB     |     1 |    47 |     2   (0)| 00:00:01 ||   2 |   UNION-ALL                   |           |       |       |            |          ||   3 |    TABLE ACCESS BY INDEX ROWID| TA        |  4998 |   229K|    18   (0)| 00:00:01 ||*  4 |     INDEX RANGE SCAN          | IDX_ID_TA |  4998 |       |    18   (0)| 00:00:01 ||   5 |    TABLE ACCESS BY INDEX ROWID| TB        |  4998 |   229K|  5016   (1)| 00:01:01 ||*  6 |     INDEX RANGE SCAN          | IDX_ID_TB |  4998 |       |    17   (0)| 00:00:01 |-------------------------------------------------------------------------------------------Predicate Information (identified by operation id):---------------------------------------------------4 - access("ID"<2500)6 - access("ID"<2500)yang@rac1>

对于创建视图的时候包含表的别名的情况：

yang@rac1>CREATE VIEW V_Tab02 AS2   SELECT * FROM TA t13  UNION ALL4    SELECT * FROM TB t2 ;View created.yang@rac1> SELECT /*+ index(tb  idx_id_tb) index(ta idx_id) */* 2     FROM V_TAB023     WHERE ID<2500;9996 rows selected.Execution Plan----------------------------------------------------------Plan hash value: 3023640653-------------------------------------------------------------------------------| Id  | Operation           | Name    | Rows  | Bytes | Cost (%CPU)| Time     |-------------------------------------------------------------------------------|   0 | SELECT STATEMENT    |         |     1 |    47 |     2   (0)| 00:00:01 ||   1 |  VIEW               | V_TAB02 |     1 |    47 |     2   (0)| 00:00:01 ||   2 |   UNION-ALL         |         |       |       |            |          ||*  3 |    TABLE ACCESS FULL| TA      |  4998 |   229K|     9   (0)| 00:00:01 ||*  4 |    TABLE ACCESS FULL| TB      |  4998 |   229K|     9   (0)| 00:00:01 |-------------------------------------------------------------------------------Predicate Information (identified by operation id):---------------------------------------------------3 - filter("ID"<2500)4 - filter("ID"<2500)

yang@rac1> SELECT /*+ index(v_tab02.tb  idx_id_tb) index(v_tab02.ta idx_id) */* 2     FROM V_TAB023     WHERE ID<2500;9996 rows selected.Execution Plan----------------------------------------------------------Plan hash value: 3023640653-------------------------------------------------------------------------------| Id  | Operation           | Name    | Rows  | Bytes | Cost (%CPU)| Time     |-------------------------------------------------------------------------------|   0 | SELECT STATEMENT    |         |     1 |    47 |     2   (0)| 00:00:01 ||   1 |  VIEW               | V_TAB02 |     1 |    47 |     2   (0)| 00:00:01 ||   2 |   UNION-ALL         |         |       |       |            |          ||*  3 |    TABLE ACCESS FULL| TA      |  4998 |   229K|     9   (0)| 00:00:01 ||*  4 |    TABLE ACCESS FULL| TB      |  4998 |   229K|     9   (0)| 00:00:01 |-------------------------------------------------------------------------------Predicate Information (identified by operation id):---------------------------------------------------3 - filter("ID"<2500)4 - filter("ID"<2500)

==此时必须使用创建视图的表的相对应的别名(VIVE.TAB_ALIAS_NAME INDEX_NAME)

yang@rac1> SELECT /*+ index(v_tab02.t2  idx_id_tb) index(v_tab02.t1 idx_id) */* 2     FROM V_TAB023     WHERE ID<2500;9996 rows selected.Execution Plan----------------------------------------------------------Plan hash value: 3173198873-------------------------------------------------------------------------------------------| Id  | Operation                     | Name      | Rows  | Bytes | Cost (%CPU)| Time     |-------------------------------------------------------------------------------------------|   0 | SELECT STATEMENT              |           |     1 |    47 |     2   (0)| 00:00:01 ||   1 |  VIEW                         | V_TAB02   |     1 |    47 |     2   (0)| 00:00:01 ||   2 |   UNION-ALL                   |           |       |       |            |          ||   3 |    TABLE ACCESS BY INDEX ROWID| TA        |  4998 |   229K|    18   (0)| 00:00:01 ||*  4 |     INDEX RANGE SCAN          | IDX_ID    |  4998 |       |    18   (0)| 00:00:01 ||   5 |    TABLE ACCESS BY INDEX ROWID| TB        |  4998 |   229K|  5016   (1)| 00:01:01 ||*  6 |     INDEX RANGE SCAN          | IDX_ID_TB |  4998 |       |    17   (0)| 00:00:01 |-------------------------------------------------------------------------------------------Predicate Information (identified by operation id):---------------------------------------------------4 - access("ID"<2500)6 - access("ID"<2500)Note------ dynamic sampling used for this statement (level=2)

转载于:https://www.cnblogs.com/emilyyoucan/p/7873041.html

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