Question

我从之前question关于SQL的好答案中获得灵感。现在，这个SQL在带有Interbase 2009的数据库上运行。它的大小约为21 GB。

SELECT DistanceAsMeters, AddrDistance.Bold_Id, AddrDistance.Created, AddressFrom.CityName_CO as FromCity, AddressTo.CityName_CO as ToCity
FROM AddrDistance
LEFT JOIN Address AddressFrom ON AddrDistance.FromAddress = AddressFrom.Bold_Id
LEFT JOIN Address AddressTo ON AddrDistance.ToAddress = AddressTo.Bold_Id
Where  DistanceAsMeters = 0 and PseudoDistanceAsCostKm = 0
       and not AddrDistance.bold_id in (select bold_id from DistanceQueryTask)
Order By Created Desc

AddrDistance有840000行带有地址的190000行和带有DistanceQueryTask的4。

问题是，这可以更快地完成吗？我想，同样的查询运行多次从DistanceQueryTask中选择bold_id 。请注意，我对存储过程不感兴趣，只是简单的SQL：）

EDIT1 以下是当前的执行计划：

Statement: SELECT DistanceAsMeters, AddrDistance.Bold_Id, AddrDistance.Created, AddressFrom.CityName_CO as FromCity, AddressTo.CityName_CO as ToCity
FROM AddrDistance
LEFT JOIN Address AddressFrom ON AddrDistance.FromAddress = AddressFrom.Bold_Id
LEFT JOIN Address AddressTo ON AddrDistance.ToAddress = AddressTo.Bold_Id
Where  DistanceAsMeters = 0 and PseudoDistanceAsCostKm = 0
       and not AddrDistance.bold_id in (select bold_id from DistanceQueryTask)
Order By Created Desc

PLAN (DISTANCEQUERYTASK INDEX (RDB$PRIMARY218))
PLAN SORT (JOIN (JOIN (ADDRDISTANCE NATURAL,ADDRESSFROM INDEX (RDB$PRIMARY234)),ADDRESSTO INDEX (RDB$PRIMARY234)))

是的，如果数据库中有行，则DistanceQueryTask意味着数字较小。

Answer 1

使用左连接和子查询会减慢任何查询速度。

您可以使用正确的索引（在Bold_id，DistanceMeters，PseudoDistanceAsCostKm上）进行一些改进，记住更多索引会增加数据库的大小

Answer 2

我认为bold_id是你的关键，因此被正确编入索引然后通过连接替换subselect和not ... in可能有助于优化器。

SELECT DistanceAsMeters, Bold_Id, Created, AddressFrom.CityName_CO as FromCity, AddressTo.CityName_CO as ToCity
FROM AddrDistance
LEFT JOIN Address AddressFrom ON AddrDistance.FromAddress = AddressFrom.Bold_Id
LEFT JOIN Address AddressTo ON AddrDistance.ToAddress = AddressTo.Bold_Id
LEFT JOIN DistanceQueryTask ON AddrDistance.bold_id = DistanceQueryTask.bold_id
Where  DistanceAsMeters = 0 and PseudoDistanceAsCostKm = 0
  and DistanceQueryTask.bold_id is null
Order By Created Desc

Answer 3

为此部分创建索引：（DistanceAsMeters = 0且PseudoDistanceAsCostKm = 0）因为它对它进行（坏）表扫描：ADDRDISTANCE NATURAL

尝试使用连接而不是Francois所述的subselect。

Answer 4

丹尼尔和安德烈建议索引有很多帮助我建议使用这个索引（DistanceMeters，PseudoDistanceAsCostKm，Bold_id），因为索引的前两部分是常量，然后是读取所需索引的一小部分。

如果存在FromAddress和/或ToAddress这一事实，您可以将LEFT JOIN更改为INNER JOIN，因为它通常更快（查询优化器可以做出一些假设）。

使用Interbase优化SQL

4 个答案: