Oracle SQL-使用dblink时未发生视图推送谓词
我在执行以下查询Q1时遇到性能问题： 小表b2包含大约200条记录，所有列都是varchar2 执行Q1有很好的表现，执行计划如下：Oracle SQL-使用dblink时未发生视图推送谓词,sql,oracle,view,sql-execution-plan,database-link,Sql,Oracle,View,Sql Execution Plan,Database Link,我在执行以下查询Q1时遇到性能问题： 小表b2包含大约200条记录，所有列都是varchar2 执行Q1有很好的表现，执行计划如下： Plan hash value: 2906430222 --------------------------------------------------------
Plan hash value: 2906430222
-----------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
-----------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 274 | 64 (0)| 00:00:01 | | |
|* 1 | COUNT STOPKEY | | | | | | | |
| 2 | NESTED LOOPS | | 1 | 274 | 64 (0)| 00:00:01 | | |
| 3 | PARTITION LIST ALL | | 1 | 22 | 59 (0)| 00:00:01 | 1 | 2 |
| 4 | PARTITION RANGE ALL | | 1 | 22 | 59 (0)| 00:00:01 | 1 | LAST |
| 5 | TABLE ACCESS BY LOCAL INDEX ROWID| ORDERS | 1 | 22 | 59 (0)| 00:00:01 | 1 | 29 |
|* 6 | INDEX RANGE SCAN | IDX_ORDERS_CREATED | 1 | | 57 (0)| 00:00:01 | 1 | 29 |
| 7 | VIEW PUSHED PREDICATE | TEST | 1 | 252 | 5 (0)| 00:00:01 | | |
|* 8 | FILTER | | | | | | | |
| 9 | SORT AGGREGATE | | 1 | 55 | | | | |
| 10 | NESTED LOOPS | | 259 | 14245 | 5 (0)| 00:00:01 | | |
|* 11 | INDEX UNIQUE SCAN | PK_ID | 1 | 14 | 2 (0)| 00:00:01 | | |
|* 12 | INDEX STORAGE FAST FULL SCAN | IDX_MN_AN_AD_ALL | 259 | 10619 | 3 (0)| 00:00:01 | | |
-----------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM<10)
6 - access("A_OUT"."CREATED">TRUNC(SYSDATE@!))
8 - filter(COUNT(*)>0)
11 - access("ID"="A_OUT"."ID")
12 - storage("B2"."ATTR_1"=NVL(CASE WHEN SUBSTR("ID",(-1))<'5' THEN 'YYY' END ,'#') OR "B2"."ATTR_1"='*')
filter("B2"."ATTR_1"=NVL(CASE WHEN SUBSTR("ID",(-1))<'5' THEN 'YYY' END ,'#') OR "B2"."ATTR_1"='*')
Plan hash value: 2906430222
-----------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers |
-----------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 9 |00:00:00.01 | 223 |
|* 1 | COUNT STOPKEY | | 1 | | 9 |00:00:00.01 | 223 |
| 2 | NESTED LOOPS | | 1 | 1 | 9 |00:00:00.01 | 223 |
| 3 | PARTITION LIST ALL | | 1 | 1 | 9 |00:00:00.01 | 41 |
| 4 | PARTITION RANGE ALL | | 1 | 1 | 9 |00:00:00.01 | 41 |
| 5 | TABLE ACCESS BY LOCAL INDEX ROWID| ORDERS | 14 | 1 | 9 |00:00:00.01 | 41 |
|* 6 | INDEX RANGE SCAN | IDX_CREATED | 12 | 1 | 9 |00:00:00.01 | 33 |
| 7 | VIEW PUSHED PREDICATE | TEST | 9 | 1 | 9 |00:00:00.01 | 182 |
|* 8 | FILTER | | 9 | | 9 |00:00:00.01 | 182 |
| 9 | SORT AGGREGATE | | 9 | 1 | 9 |00:00:00.01 | 182 |
| 10 | NESTED LOOPS | | 9 | 259 | 2376 |00:00:00.01 | 182 |
|* 11 | INDEX UNIQUE SCAN | PK_ID | 9 | 1 | 9 |00:00:00.01 | 20 |
|* 12 | INDEX STORAGE FAST FULL SCAN | IDX_MN_AN_AD_ALL | 9 | 259 | 2376 |00:00:00.01 | 162 |
-----------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM<10)
6 - access("A_OUT"."CREATED">TRUNC(SYSDATE@!))
8 - filter(COUNT(*)>0)
11 - access("ID"="A_OUT"."ID")
12 - storage(("B2"."ATTR_1"=NVL(CASE WHEN SUBSTR("ID",(-1))<'5' THEN 'YYY' END ,'#') OR
"B2"."ATTR_1"='*'))
filter(("B2"."ATTR_1"=NVL(CASE WHEN SUBSTR("ID",(-1))<'5' THEN 'YYY' END ,'#') OR
"B2"."ATTR_1"='*'))
从dual中选择1始终存在，此子查询没有意义->条件并存在从中选择1dual@db2总是评估为真，因此，只需从查询中删除此条件，就可以解决此问题。@krokodilko:view测试只是一个简单的示例，旨在说明我在几行代码中遇到的问题。真实视图要复杂得多，执行计划为500多行。并退出从中选择1dual@db2用于显示即使在使用如此简单的条件时问题也会发生。出于一些好的原因，我正在使用的真实视图访问DB2；然后运行查询，然后立即运行此查询：从表dbms\u xplan.display\u cursor format=>ALLSTATS LAST'中选择*；并将上次查询的结果附加到问题。这将生成查询的真实统计信息，而不是简单解释计划生成的估计统计信息。@krokodilko:我应用了建议的过程并编辑了问题，添加了Q1的执行计划以及行和existsselect 1 fromdual@db2在未注释的视图中，对于Q1，视图中的行已注释。谢谢时间=00:00:00.01，也就是100毫秒。在我看来，100毫秒不是性能问题。A-Rows=2376，这意味着该查询只扫描约2000行，这对于DBMS来说是非常少的。是否确实要优化此查询？我猜您正在尝试优化一个完全不同的查询，如果是，那么发布您想要优化的查询计划。您无法通过查看兰博基尼的性能图来调整法拉利。从dual中选择1始终存在，此子查询没有意义->条件和存在从中选择1dual@db2总是评估为真，因此，只需从查询中删除此条件，就可以解决此问题。@krokodilko:view测试只是一个简单的示例，旨在说明我在几行代码中遇到的问题。真实视图要复杂得多，执行计划为500多行。并退出从中选择1dual@db2用于显示即使在使用如此简单的条件时问题也会发生。出于一些好的原因，我正在使用的真实视图访问DB2；然后运行查询，然后立即运行此查询：从表dbms\u xplan.display\u cursor format=>ALLSTATS LAST'中选择*；并将上次查询的结果附加到问题。这将生成查询的真实统计信息，而不是简单解释计划生成的估计统计信息。@krokodilko:我应用了建议的过程并编辑了问题，添加了Q1的执行计划以及行和existsselect 1 fromdual@db2在未注释的视图中，对于Q1，视图中的行已注释。谢谢时间=00:00:00.01，也就是100毫秒。在我看来，100毫秒不是性能问题。A-Rows=2376，这意味着该查询只扫描约2000行，这对于DBMS来说是非常少的。是否确实要优化此查询？我猜您正在尝试优化一个完全不同的查询，如果是，那么发布您想要优化的查询计划。你不能通过兰博基尼的性能图来调整法拉利。
Plan hash value: 2906430222
-----------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop |
-----------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 274 | 64 (0)| 00:00:01 | | |
|* 1 | COUNT STOPKEY | | | | | | | |
| 2 | NESTED LOOPS | | 1 | 274 | 64 (0)| 00:00:01 | | |
| 3 | PARTITION LIST ALL | | 1 | 22 | 59 (0)| 00:00:01 | 1 | 2 |
| 4 | PARTITION RANGE ALL | | 1 | 22 | 59 (0)| 00:00:01 | 1 | LAST |
| 5 | TABLE ACCESS BY LOCAL INDEX ROWID| ORDERS | 1 | 22 | 59 (0)| 00:00:01 | 1 | 29 |
|* 6 | INDEX RANGE SCAN | IDX_ORDERS_CREATED | 1 | | 57 (0)| 00:00:01 | 1 | 29 |
| 7 | VIEW PUSHED PREDICATE | TEST | 1 | 252 | 5 (0)| 00:00:01 | | |
|* 8 | FILTER | | | | | | | |
| 9 | SORT AGGREGATE | | 1 | 55 | | | | |
| 10 | NESTED LOOPS | | 259 | 14245 | 5 (0)| 00:00:01 | | |
|* 11 | INDEX UNIQUE SCAN | PK_ID | 1 | 14 | 2 (0)| 00:00:01 | | |
|* 12 | INDEX STORAGE FAST FULL SCAN | IDX_MN_AN_AD_ALL | 259 | 10619 | 3 (0)| 00:00:01 | | |
-----------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM<10)
6 - access("A_OUT"."CREATED">TRUNC(SYSDATE@!))
8 - filter(COUNT(*)>0)
11 - access("ID"="A_OUT"."ID")
12 - storage("B2"."ATTR_1"=NVL(CASE WHEN SUBSTR("ID",(-1))<'5' THEN 'YYY' END ,'#') OR "B2"."ATTR_1"='*')
filter("B2"."ATTR_1"=NVL(CASE WHEN SUBSTR("ID",(-1))<'5' THEN 'YYY' END ,'#') OR "B2"."ATTR_1"='*')
Plan hash value: 3271081243
----------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop | Inst |IN-OUT|
----------------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 288 | 5273K (1)| 00:03:27 | | | | |
|* 1 | COUNT STOPKEY | | | | | | | | | |
|* 2 | HASH JOIN | | 1 | 288 | 5273K (1)| 00:03:27 | | | | |
| 3 | JOIN FILTER CREATE | :BF0000 | 1 | 22 | 59 (0)| 00:00:01 | | | | |
| 4 | PARTITION LIST ALL | | 1 | 22 | 59 (0)| 00:00:01 | 1 | 2 | | |
| 5 | PARTITION RANGE ALL | | 1 | 22 | 59 (0)| 00:00:01 | 1 | LAST | | |
| 6 | TABLE ACCESS BY LOCAL INDEX ROWID| ORDERS | 1 | 22 | 59 (0)| 00:00:01 | 1 | 29 | | |
|* 7 | INDEX RANGE SCAN | IDX_ORDERS_CREATED | 1 | | 57 (0)| 00:00:01 | 1 | 29 | | |
| 8 | VIEW | TEST | 3840K| 974M| 5273K (1)| 00:03:27 | | | | |
| 9 | SORT GROUP BY | | 3840K| 201M| 5273K (1)| 00:03:27 | | | | |
| 10 | JOIN FILTER USE | :BF0000 | 994M| 50G| 5273K (1)| 00:03:27 | | | | |
| 11 | NESTED LOOPS | | 994M| 50G| 5273K (1)| 00:03:27 | | | | |
| 12 | INDEX FULL SCAN | PK_ID | 3840K| 51M| 66212 (1)| 00:00:03 | | | | |
|* 13 | INDEX STORAGE FAST FULL SCAN | IDX_MN_AN_AD_ALL | 259 | 10619 | 1 (0)| 00:00:01 | | | | |
| 14 | REMOTE | | | | | | | | DB2 | R->S |
----------------------------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM<10)
2 - access("A_OUT"."ID"="Z_OUT"."ID")
7 - access("A_OUT"."CREATED">TRUNC(SYSDATE@!))
13 - filter("B2"."ATTR_1"=NVL(CASE WHEN (SUBSTR("ID",(-1))<'5' AND EXISTS (SELECT 0 FROM "A1")) THEN 'YYY' END ,'#') OR
"B2"."ATTR_1"='*')
Remote SQL Information (identified by operation id):
----------------------------------------------------
14 - EXPLAIN PLAN INTO PLAN_TABLE@! FOR SELECT 0 FROM "DUAL" "A1" (accessing 'DB2' )
select
(select value from test z_out where a_out.id=z_out.id) as value,
a_out.id
from orders a_out
where a_out.created>trunc(sysdate) and rownum<10
alter session set statistics_level = 'ALL';
-- Q1 (the query I'm having problems with)
select * from table (dbms_xplan.display_cursor (format=>'ALLSTATS LAST'));
Plan hash value: 3271081243
------------------------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | Reads | OMem | 1Mem | Used-Mem |
------------------------------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 0 |00:00:00.01 | 0 | 0 | | | |
|* 1 | COUNT STOPKEY | | 1 | | 0 |00:00:00.01 | 0 | 0 | | | |
|* 2 | HASH JOIN | | 1 | 1 | 0 |00:00:00.01 | 0 | 0 | 3789K| 3789K| 1078K (0)|
| 3 | JOIN FILTER CREATE | :BF0000 | 1 | 1 | 25602 |00:00:00.22 | 23345 | 161 | | | |
| 4 | PARTITION LIST ALL | | 1 | 1 | 25602 |00:00:00.21 | 23345 | 161 | | | |
| 5 | PARTITION RANGE ALL | | 2 | 1 | 25602 |00:00:00.21 | 23345 | 161 | | | |
| 6 | TABLE ACCESS BY LOCAL INDEX ROWID| ORDERS | 29 | 1 | 25602 |00:00:00.20 | 23345 | 161 | | | |
|* 7 | INDEX RANGE SCAN | IDX_CREATED | 13 | 1 | 25602 |00:00:00.12 | 474 | 161 | 1025K| 1025K| |
| 8 | VIEW | TEST | 1 | 3820K| 0 |00:00:00.01 | 0 | 0 | | | |
| 9 | SORT GROUP BY | | 1 | 3820K| 0 |00:00:00.01 | 0 | 0 | 73728 | 73728 | |
| 10 | JOIN FILTER USE | :BF0000 | 1 | 989M| 106M|00:03:38.87 | 60M| 52960 | | | |
| 11 | NESTED LOOPS | | 1 | 989M| 328M|00:03:04.11 | 60M| 52960 | | | |
| 12 | INDEX FULL SCAN | PK_ID | 1 | 3820K| 1245K|00:00:21.04 | 200K| 52959 | 1025K| 1025K| |
|* 13 | INDEX STORAGE FAST FULL SCAN | IDX_MN_AN_AD_ALL | 1245K| 259 | 328M|00:02:12.09 | 60M| 1 | 1025K| 1025K| |
| 14 | REMOTE | | 1 | | 1 |00:00:00.01 | 0 | 0 | | | |
------------------------------------------------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM<10)
2 - access("A_OUT"."ID"="Z_OUT"."ID")
7 - access("A_OUT"."CREATED">TRUNC(SYSDATE@!))
13 - filter(("B2"."ATTR_1"=NVL(CASE WHEN (SUBSTR("ID",(-1))<'5' AND IS NOT NULL) THEN 'YYY' END ,'#') OR "B2"."ATTR_1"='*'))
Plan hash value: 2906430222
-----------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers |
-----------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 9 |00:00:00.01 | 223 |
|* 1 | COUNT STOPKEY | | 1 | | 9 |00:00:00.01 | 223 |
| 2 | NESTED LOOPS | | 1 | 1 | 9 |00:00:00.01 | 223 |
| 3 | PARTITION LIST ALL | | 1 | 1 | 9 |00:00:00.01 | 41 |
| 4 | PARTITION RANGE ALL | | 1 | 1 | 9 |00:00:00.01 | 41 |
| 5 | TABLE ACCESS BY LOCAL INDEX ROWID| ORDERS | 14 | 1 | 9 |00:00:00.01 | 41 |
|* 6 | INDEX RANGE SCAN | IDX_CREATED | 12 | 1 | 9 |00:00:00.01 | 33 |
| 7 | VIEW PUSHED PREDICATE | TEST | 9 | 1 | 9 |00:00:00.01 | 182 |
|* 8 | FILTER | | 9 | | 9 |00:00:00.01 | 182 |
| 9 | SORT AGGREGATE | | 9 | 1 | 9 |00:00:00.01 | 182 |
| 10 | NESTED LOOPS | | 9 | 259 | 2376 |00:00:00.01 | 182 |
|* 11 | INDEX UNIQUE SCAN | PK_ID | 9 | 1 | 9 |00:00:00.01 | 20 |
|* 12 | INDEX STORAGE FAST FULL SCAN | IDX_MN_AN_AD_ALL | 9 | 259 | 2376 |00:00:00.01 | 162 |
-----------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM<10)
6 - access("A_OUT"."CREATED">TRUNC(SYSDATE@!))
8 - filter(COUNT(*)>0)
11 - access("ID"="A_OUT"."ID")
12 - storage(("B2"."ATTR_1"=NVL(CASE WHEN SUBSTR("ID",(-1))<'5' THEN 'YYY' END ,'#') OR
"B2"."ATTR_1"='*'))
filter(("B2"."ATTR_1"=NVL(CASE WHEN SUBSTR("ID",(-1))<'5' THEN 'YYY' END ,'#') OR
"B2"."ATTR_1"='*'))