Linq2SQL：优化查询？

Question

我可以通过任何方式优化以下查询：

目标是尝试找到类型4的客户，该类型4也基于其增值税和电子邮件而存在为类型2。客户端可以有一个或多个客户端用户。

（我都合适的指标设置，我保证）

from e in Clients.Where(h => h.ClientTypeId==4) 
join u in ClientUsers on e.Id equals u.ClientId 
where 
e.DeleteFlag.Equals("n") && 
(

    (!(e.VAT == null || e.VAT.Equals("")) && Clients.Any(f => f.ClientTypeId == 2 && f.VAT.Equals(e.VAT))) 

    || (!(e.Email == null || e.Email.Equals("")) && 
     (
      Clients.Any(f => f.ClientTypeId == 2 && f.Email.ToLower().Equals(e.Email.ToLower())) 
      || (from f in ClientUsers join q in Clients on f.ClientId equals q.Id where f.Email.Equals(e.Email.ToLower()) && q.ClientTypeId == 2 select f.Id).Any() 
     ) 
    ) 

    || (!(u.Email == null || u.Email.Equals("")) && 
     (
      Clients.Any(f => f.ClientTypeId == 2 && f.Email.ToLower().Equals(u.Email.ToLower())) 
      || (from f in ClientUsers join q in Clients on f.ClientId equals q.Id where f.Email.Equals(u.Email.ToLower()) && q.ClientTypeId == 2 select f.Id).Any() 
     ) 
    ) 

) 
select e 

结果：

-- Region Parameters 
DECLARE @p0 VarChar(1) SET @p0 = 'n' 
DECLARE @p1 NVarChar(1) SET @p1 = '' 
DECLARE @p2 Int SET @p2 = 2 
DECLARE @p3 NVarChar(1) SET @p3 = '' 
DECLARE @p4 Int SET @p4 = 2 
DECLARE @p5 Int SET @p5 = 2 
DECLARE @p6 NVarChar(1) SET @p6 = '' 
DECLARE @p7 Int SET @p7 = 2 
DECLARE @p8 Int SET @p8 = 2 
DECLARE @p9 Int SET @p9 = 4 
-- EndRegion 
SELECT [t0].[Id], [t0].[AccountId], [t0].[CompanyName], [t0].[Address], [t0].[Address2], [t0].[PostCode], [t0].[PostArea], [t0].[ContactPerson], [t0].[Phone], [t0].[Email], [t0].[VAT], [t0].[Webpage], [t0].[Description], [t0].[Active], [t0].[PreRegcode], [t0].[PreRegcheck], [t0].[AccountCreated], [t0].[UpdateTimeStamp], [t0].[DeleteFlag], [t0].[ClientTypeId], [t0].[CampaignCodeId], [t0].[PayexId], [t0].[ApiKey], [t0].[InvoiceName], [t0].[Source], [t0].[ProspectStatusId], [t0].[ProspectLastCommentId], [t0].[ProspectCallbackDate] 
FROM [Clients] AS [t0] 
INNER JOIN [ClientUsers] AS [t1] ON ([t0].[Id]) = [t1].[ClientId] 
WHERE ([t0].[DeleteFlag] = @p0) AND (((NOT (([t0].[VAT] IS NULL) OR ([t0].[VAT] = @p1))) AND (EXISTS(
    SELECT NULL AS [EMPTY] 
    FROM [Clients] AS [t2] 
    WHERE ([t2].[ClientTypeId] = @p2) AND ([t2].[VAT] = [t0].[VAT]) 
    ))) OR ((NOT (([t0].[Email] IS NULL) OR ([t0].[Email] = @p3))) AND ((EXISTS(
    SELECT NULL AS [EMPTY] 
    FROM [Clients] AS [t3] 
    WHERE ([t3].[ClientTypeId] = @p4) AND (LOWER([t3].[Email]) = LOWER([t0].[Email])) 
    )) OR (EXISTS(
    SELECT NULL AS [EMPTY] 
    FROM [ClientUsers] AS [t4] 
    INNER JOIN [Clients] AS [t5] ON [t4].[ClientId] = ([t5].[Id]) 
    WHERE ([t4].[Email] = LOWER([t0].[Email])) AND ([t5].[ClientTypeId] = @p5) 
    )))) OR ((NOT (([t1].[Email] IS NULL) OR ([t1].[Email] = @p6))) AND ((EXISTS(
    SELECT NULL AS [EMPTY] 
    FROM [Clients] AS [t6] 
    WHERE ([t6].[ClientTypeId] = @p7) AND (LOWER([t6].[Email]) = LOWER([t1].[Email])) 
    )) OR (EXISTS(
    SELECT NULL AS [EMPTY] 
    FROM [ClientUsers] AS [t7] 
    INNER JOIN [Clients] AS [t8] ON [t7].[ClientId] = ([t8].[Id]) 
    WHERE ([t7].[Email] = LOWER([t1].[Email])) AND ([t8].[ClientTypeId] = @p8) 
    ))))) AND ([t0].[ClientTypeId] = @p9) 

查询工作，但需要5分钟来运行。

Answer 1

你使用的是什么数据库排序规则？查询可以进行重组，简化了一点，但首先它可能是一个想法，删除所有.ToLower等等，除非你使用的是区分大小写的整理...

编辑：你可以尝试改变你的查询一些较小的联合查询让sql优化器没有创造性的自由......（查询中的许多'或'条件往往会导致扫描，即使有覆盖索引）。

例如为：

(

from e in dc.Clients 
join u in dc.ClientUsers on e.Id equals u.ClientId 
join vc in dc.Clients on new { ClientTypeId = 2, e.VAT } equals new { vc.ClientTypeId, vc.VAT } 
where e.ClientTypeId == 4 
    && e.DeleteFlag.Equals("n") 
    && e.VAT != null 
    && e.VAT != "" 
select e 

).Union(

from e in dc.Clients 
join u in dc.ClientUsers on e.Id equals u.ClientId 
join ec in dc.Clients on new { ClientTypeId = 2, e.Email } equals new { ec.ClientTypeId, ec.Email } 
where e.ClientTypeId == 4 
&& e.DeleteFlag.Equals("n") 
&& e.Email != null 
&& e.Email != "" 
select e 

).Union(

from e in dc.Clients 
join u in dc.ClientUsers on e.Id equals u.ClientId 
join c1u in dc.ClientUsers on e.Email equals new c1u.Email 
join c1c in dc.Clients on new { ClientTypeId = 2, c1u.ClientId } equals new { c1c.ClientTypeId, ClientId = c1c.Id } 
where e.ClientTypeId==4 
&& e.DeleteFlag.Equals("n") 
&& e.Email != null 
&& e.Email != "" 
select e 

).Union(

from e in dc.Clients 
join u in dc.ClientUsers on e.Id equals u.ClientId 
join c2u in dc.ClientUsers on u.Email equals c2u.Email 
join c2c in dc.Clients on new { ClientTypeId = 2, c2u.ClientId } equals new { c2c.ClientTypeId, ClientId = c2c.Id } 
where e.ClientTypeId==4 
&& e.DeleteFlag.Equals("n") 
&& u.Email != null 
&& u.Email != "" 
select e 

)