调优 SQL 语句性能

Question

我有两个返回相同结果的查询：

1.

SELECT DISTINCT 
         cvc.object_id
        , cvc.object_name  
 FROM ems.ibo_sm_cvc_rfs cvc,  
      ems.ibo_alcatel_mse_locale poi, 
      ems.ibo_nbn_csa csa, 
      ems.ibo_sm_ean_service_sites_rfs sites, 
      ems.ibo_sm_ean_service_site_rfs site  
WHERE poi.object_name ='testPoi'  
  AND csa.parent_id = poi.object_id  
  AND cvc.csa_id = csa.csa_id  
  AND sites.parent_id = cvc.object_id  
  AND site.service_site_type = 'testSite'  
  AND site.object_name IN (SELECT mse_chassis.object_name  
                             FROM ems.ibo_alcatel_mse_chassis mse_chassis  
                            WHERE mse_chassis.parent_id = poi.object_id);

2。 ：

SELECT cvc.object_id,
       cvc.object_name
  FROM ems.ibo_sm_cvc_rfs cvc
  JOIN ems.ibo_nbn_csa csa
    ON cvc.csa_id = csa.csa_id
  JOIN ems.ibo_sm_ean_service_sites_rfs sites
    ON sites.parent_id   = cvc.object_id
 WHERE csa.parent_id IN (SELECT poi.object_id
                           FROM ems.ibo_alcatel_mse_locale poi
                          WHERE poi.object_id IN (SELECT csa.parent_id FROM ems.ibo_nbn_csa csa)
                             AND poi.object_name = 'testPoi'
                             AND poi.object_id  IN 
                                 (SELECT mse_chassis.parent_id
                                    FROM EMS.ibo_alcatel_mse_chassis mse_chassis
                                   WHERE mse_chassis.object_name IN
                                         (SELECT site.object_name
                                            FROM EMS.ibo_sm_ean_service_site_rfs site
                                           WHERE site.service_site_type = 'testSite')
                                 )
                         );

对我来说奇怪的是，第一个语句在 0.156 秒内完成，而第二个语句在 0.624 秒内完成。需要提一下，所有 ems.* 对象都是视图，我发现基本上 where 子句中的每一列都被索引了。 如果需要，我可以放置视图架构，但我宁愿不要，因为是公司信息。也许一双经验的眼睛可能会看到这两种说法的改进

Answer 1

正如@Mihai 指出的那样，您的第二个查询充满了子查询，我会再进一步​​微调您发布的第一个查询，如下所示

SELECT DISTINCT 
    cvc.object_id
    , cvc.object_name  
FROM ems.ibo_sm_cvc_rfs cvc 
    JOIN ems.ibo_nbn_csa csa ON cvc.csa_id = csa.csa_id
    JOIN ems.ibo_alcatel_mse_locale poi ON csa.parent_id = poi.object_id 
    JOIN ems.ibo_sm_ean_service_sites_rfs sites ON sites.parent_id = cvc.object_id 
    JOIN EMS.ibo_alcatel_mse_chassis mse_chassis ON mse_chassis.parent_id = poi.object_id
    JOIN EMS.ibo_sm_ean_service_site_rfs site ON site.object_name = mse_chassis.object_name
WHERE poi.object_name ='testPoi' 
AND site.service_site_type = 'testSite';

注意两点：

1. 我已将您的隐式连接语法修改为显式连接语法

2. 我已将您的最后一个带有IN 子句的子查询修改为JOIN 语句

Answer 2

SELECT 
    cvc.object_id
    , cvc.object_name  
FROM ems.ibo_sm_cvc_rfs cvc,  
    ems.ibo_alcatel_mse_locale poi, 
    ems.ibo_nbn_csa csa, 
    ems.ibo_sm_ean_service_sites_rfs sites, 
    EMS.ibo_sm_ean_service_site_rfs site,
    EMS.ibo_alcatel_mse_chassis mse_chassis  
WHERE poi.object_name ='testPoi'  
    AND csa.parent_id = poi.object_id  
    AND cvc.csa_id = csa.csa_id  
    AND sites.parent_id = cvc.object_id  
    AND site.service_site_type = 'testSite'  
    AND site.object_name = mse_chassis.object_name  
    AND mse_chassis.parent_id = poi.object_id 
GROUP BY cvc.object_id, cvc.object_name 

旨在进行非常有效的松散索引扫描，因此添加此索引

CREATE INDEX objects_idx
  ON ibo_sm_cvc_rfs (object_id, object_name);