加入Oracle时查询速度慢，分裂成两个查询时速度快

我有一个sql查询，当连接两个表时速度很慢，但当我第一次查询一个表并且查询另一个表时，速度很快。加入Oracle时查询速度慢，分裂成两个查询时速度快

环境/先决条件

Oracle版本：
Oracle数据库11g企业版发布11.2.0.3.0 - 64位生产

对象涉及：
cfc_materialized（物化视图，21.5神达行）
contact（table，12,6 Mio rows）

涉及的指标：
CREATE INDEX CONTACT_CLIENT ON CONTACT（客户）;
CREATE INDEX CFC_MATERIALIZED_A_S_T ON CFC_MATERIALIZED（ASSOCIATION_TYPE，SOURCEID，TARGETID）;

我已经重新计算2代表与级联的统计=>真：

BEGIN 
    SYS.DBMS_STATS.GATHER_TABLE_STATS (
    OwnName  => '...' 
    ,TabName  => '...' 
    ,Estimate_Percent => 0 
    ,Degree   => 4 
    ,Cascade   => TRUE 
    ,No_Invalidate  => FALSE); 
END; 
/

问题

我有以下查询：

SELECT c.* 
FROM contact c 
WHERE c.client in (
    SELECT cfc.targetid 
    FROM cfc_materialized cfc 
    WHERE cfc.sourceid = 'e95027f0-a83e-11e3-a0ae-005056aebabc' 
     AND cfc.association_type = 'ContactDataSharing' 
) 
    AND c.deleted = 0;

解释计划：

-------------------------------------------------------------------------------------------------------------------------------- 
| Id | Operation      | Name    | Rows | Bytes | Cost (%CPU)| Time  | TQ |IN-OUT| PQ Distrib | 
-------------------------------------------------------------------------------------------------------------------------------- 
| 0 | SELECT STATEMENT    |     | 11M| 2214M| 38976 (1)| 00:07:48 |  |  |   | 
| 1 | PX COORDINATOR    |     |  |  |   |   |  |  |   | 
| 2 | PX SEND QC (RANDOM)   | :TQ10001   |  |  |   |   | Q1,01 | P->S | QC (RAND) | 
| 3 | NESTED LOOPS    |     |  |  |   |   | Q1,01 | PCWP |   | 
| 4 |  NESTED LOOPS    |     | 11M| 2214M| 38976 (1)| 00:07:48 | Q1,01 | PCWP |   | 
| 5 |  SORT UNIQUE    |     | 2164 | 196K| 10672 (1)| 00:02:09 | Q1,01 | PCWP |   | 
| 6 |  PX RECEIVE    |     | 2164 | 196K| 10672 (1)| 00:02:09 | Q1,01 | PCWP |   | 
| 7 |  PX SEND HASH   | :TQ10000   | 2164 | 196K| 10672 (1)| 00:02:09 | Q1,00 | P->P | HASH  | 
| 8 |   PX BLOCK ITERATOR  |     | 2164 | 196K| 10672 (1)| 00:02:09 | Q1,00 | PCWC |   | 
|* 9 |   MAT_VIEW ACCESS FULL | CFC_MATERIALIZED | 2164 | 196K| 10672 (1)| 00:02:09 | Q1,00 | PCWP |   | 
|* 10 |  INDEX RANGE SCAN   | CONTACT_CLIENT | 5500 |  | 37 (0)| 00:00:01 | Q1,01 | PCWP |   | 
|* 11 |  TABLE ACCESS BY INDEX ROWID| CONTACT   | 5474 | 550K| 973 (0)| 00:00:12 | Q1,01 | PCWP |   | 
-------------------------------------------------------------------------------------------------------------------------------- 

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

    9 - filter("CFC"."SOURCEID"='e95027f0-a83e-11e3-a0ae-005056aebabc' AND "CFC"."ASSOCIATION_TYPE"='ContactDataSharing') 
    10 - access("C"."CLIENT"="CFC"."TARGETID") 
    11 - filter("C"."DELETED"=0)enter code here

这需要很长时间，我想知道为什么在cfc_materialized上有完整的访问权限。将查询拆分为2个查询时，速度要快得多。第一次查询：

SELECT cfc.targetid 
FROM cfc_materialized cfc 
WHERE cfc.sourceid = 'e95027f0-a83e-11e3-a0ae-005056aebabc' 
    AND cfc.association_type = 'ContactDataSharing';

该查询返回2个targetids。解释计划：

------------------------------------------------------------------------------------------- 
| Id | Operation  | Name     | Rows | Bytes | Cost (%CPU)| Time  | 
------------------------------------------------------------------------------------------- 
| 0 | SELECT STATEMENT |      | 2164 | 196K| 36 (0)| 00:00:01 | 
|* 1 | INDEX RANGE SCAN| CFC_MATERIALIZED_A_S_T | 2164 | 196K| 36 (0)| 00:00:01 | 
------------------------------------------------------------------------------------------- 

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

    1 - access("CFC"."ASSOCIATION_TYPE"='ContactDataSharing' AND 
       "CFC"."SOURCEID"='e95027f0-a83e-11e3-a0ae-005056aebabc')

这里是第二个查询。我用的第一个查询的输出作为输入的IN参数：

SELECT * 
FROM contact c 
WHERE c.client in (
    'e95027f0-a83e-11e3-a0ae-005056aebabc', 
    'eb37d3b0-a83e-11e3-a0ae-005056aebabc' 
) 
    AND c.deleted = 0;

解释计划：

----------------------------------------------------------------------------------------------- 
| Id | Operation     | Name   | Rows | Bytes | Cost (%CPU)| Time  | 
----------------------------------------------------------------------------------------------- 
| 0 | SELECT STATEMENT    |    | 2814 | 283K| 505 (0)| 00:00:07 | 
| 1 | INLIST ITERATOR    |    |  |  |   |   | 
|* 2 | TABLE ACCESS BY INDEX ROWID| CONTACT  | 2814 | 283K| 505 (0)| 00:00:07 | 
|* 3 | INDEX RANGE SCAN   | CONTACT_CLIENT | 2827 |  | 23 (0)| 00:00:01 | 
----------------------------------------------------------------------------------------------- 

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

    2 - filter("C"."DELETED"=0) 
    3 - access("C"."CLIENT"='e95027f0-a83e-11e3-a0ae-005056aebabc' OR 
       "C"."CLIENT"='eb37d3b0-a83e-11e3-a0ae-005056aebabc')

问题

所以我的问题是，为什么是CBO不以类似的方式执行查询，例如手动执行2个查询中的查询。我也试图与提示查询在2个查询使用相同的指标，如：

SELECT /*+ index(c CONTACT_CLIENT) */ c.* 
FROM contact c 
WHERE c.client in (
    SELECT /*+ index(cfc CFC_MATERIALIZED_A_S_T) */ cfc.targetid 
    FROM cfc_materialized cfc 
    WHERE cfc.sourceid = 'e95027f0-a83e-11e3-a0ae-005056aebabc' 
     AND cfc.association_type = 'ContactDataSharing' 
) 
    AND c.deleted = 0;

但后来我得到一个更糟糕的解释计划：

------------------------------------------------------------------------------------------------------- 
| Id | Operation     | Name     | Rows | Bytes | Cost (%CPU)| Time  | 
------------------------------------------------------------------------------------------------------- 
| 0 | SELECT STATEMENT    |      | 11M| 2214M| 305K (1)| 01:01:09 | 
| 1 | NESTED LOOPS    |      |  |  |   |   | 
| 2 | NESTED LOOPS    |      | 11M| 2214M| 305K (1)| 01:01:09 | 
| 3 | SORT UNIQUE    |      | 2164 | 196K| 36 (0)| 00:00:01 | 
|* 4 |  INDEX RANGE SCAN   | CFC_MATERIALIZED_A_S_T | 2164 | 196K| 36 (0)| 00:00:01 | 
|* 5 | INDEX RANGE SCAN   | CONTACT_CLIENT   | 5500 |  | 37 (0)| 00:00:01 | 
|* 6 | TABLE ACCESS BY INDEX ROWID| CONTACT    | 5474 | 550K| 973 (0)| 00:00:12 | 
------------------------------------------------------------------------------------------------------- 

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

    4 - access("CFC"."ASSOCIATION_TYPE"='ContactDataSharing' AND 
       "CFC"."SOURCEID"='e95027f0-a83e-11e3-a0ae-005056aebabc') 
    5 - access("C"."CLIENT"="CFC"."TARGETID") 
    6 - filter("C"."DELETED"=0)

我也试图做一个连接，而不是IN子句的像亚历山大和StanislavL建议：

SELECT c.* 
FROM contact c 
JOIN cfc_materialized cfc ON c.client = cfc.targetid 
WHERE cfc.sourceid = 'e95027f0-a83e-11e3-a0ae-005056aebabc' 
    AND cfc.association_type = 'ContactDataSharing' 
    AND c.deleted = 0;

，并得到了以下解释计划，这又是很慢（比两个单独的查询速度较慢）：

--------------------------------------------------------------------------------------------- 
| Id | Operation   | Name     | Rows | Bytes | Cost (%CPU)| Time  | 
--------------------------------------------------------------------------------------------- 
| 0 | SELECT STATEMENT |      | 11M| 2214M| 51745 (1)| 00:10:21 | 
|* 1 | HASH JOIN   |      | 11M| 2214M| 51745 (1)| 00:10:21 | 
|* 2 | INDEX RANGE SCAN | CFC_MATERIALIZED_A_S_T | 2164 | 196K| 36 (0)| 00:00:01 | 
|* 3 | TABLE ACCESS FULL| CONTACT    | 12M| 1237M| 51649 (1)| 00:10:20 | 
--------------------------------------------------------------------------------------------- 

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

    1 - access("C"."CLIENT"="CFC"."TARGETID") 
    2 - access("CFC"."ASSOCIATION_TYPE"='ContactDataSharing' AND 
       "CFC"."SOURCEID"='e95027f0-a83e-11e3-a0ae-005056aebabc') 
    3 - filter("C"."DELETED"=0)

来源

2014-03-25 Max

另外，我相信，在这里需要'cfc_materialized.targetid'上的索引 – Alexander

SELECT c.* 
FROM contact c 
    join (
    SELECT cfc.targetid as client 
    FROM cfc_materialized cfc 
    WHERE cfc.sourceid = 'e95027f0-a83e-11e3-a0ae-005056aebabc' 
     AND cfc.association_type = 'ContactDataSharing' 
) sub ON c.client=sub.client 
    AND c.deleted = 0;

使用加入，而不是IN避免WHERE

来源

2014-03-25 09:04:59 StanislavL

为什么你认为查询将被计算多次？ – Alexander

每一行的同一个查询的计算主要是，避免在Contact表的全表的访问。避免c.*，指定列的具体列表。重建索引

CREATE INDEX CFC_MATERIALIZED_A_S_T ON CFC_MATERIALIZED(TARGETID, ASSOCIATION_TYPE, SOURCEID);

控制连接顺序访问。

让我知道。

来源

2014-06-08 10:35:00 user3719461

加入Oracle时查询速度慢，分裂成两个查询时速度快

回答

相关问题