我想说万恶之源从这里开始：
where acl.ToIds().Contains(r.PersonOrGroupID)
这acl.ToIds().Contains(...)是一个无法在服务器端解析的表达式，因此visible必须在客户端解析查询（非常无效），更糟糕的是，结果必须保留在客户端，然后在迭代时，thre对于每个可见的约会（约会字段、角色和注释），必须将不同的查询发送到服务器。如果我有自己的想法，我会创建一个存储过程，它接受 ACL 列表作为表值参数，并在服务器端执行所有加入/过滤。
我将从这个模式开始：
create table Appointments (
AppointmentID int not null identity(1,1),
Start DateTime not null,
[End] DateTime not null,
Location varchar(100),
constraint PKAppointments
primary key nonclustered (AppointmentID));
create table AppointmentRoles (
AppointmentID int not null,
PersonOrGroupID int not null,
Role int not null,
constraint PKAppointmentRoles
primary key (PersonOrGroupID, AppointmentID),
constraint FKAppointmentRolesAppointmentID
foreign key (AppointmentID)
references Appointments(AppointmentID));
create table AppointmentNotes (
AppointmentID int not null,
NoteId int not null,
Note varchar(max),
constraint PKAppointmentNotes
primary key (AppointmentID, NoteId),
constraint FKAppointmentNotesAppointmentID
foreign key (AppointmentID)
references Appointments(AppointmentID));
go
create clustered index cdxAppointmentStart on Appointments (Start, [End]);
go
并检索任意 ACL 的约会，如下所示：
create type AccessControlList as table
(PersonOrGroupID int not null);
go
create procedure usp_getAppointmentsForACL
@acl AccessControlList readonly,
@start datetime,
@end datetime
as
begin
set nocount on;
select a.AppointmentID
, a.Location
, r.Role
, n.NoteID
, n.Note
from @acl l
join AppointmentRoles r on l.PersonOrGroupID = r.PersonOrGroupID
join Appointments a on r.AppointmentID = a.AppointmentID
join AppointmentNotes n on n.AppointmentID = a.AppointMentID
where a.Start >= @start
and a.[End] <= @end;
end
go
让我们在 1M 的约会上试试这个。首先，填充表格（大约需要 4-5 分钟）：
set nocount on;
declare @i int = 0;
begin transaction;
while @i < 1000000
begin
declare @start datetime, @end datetime;
set @start = dateadd(hour, rand()*10000-5000, getdate());
set @end = dateadd(hour, rand()*100, @start)
insert into Appointments (Start, [End], Location)
values (@start, @end, replicate('X', rand()*100));
declare @appointmentID int = scope_identity();
declare @atendees int = rand() * 10.00 + 1.00;
while @atendees > 0
begin
insert into AppointmentRoles (AppointmentID, PersonOrGroupID, Role)
values (@appointmentID, @atendees*100 + rand()*100, rand()*10);
set @atendees -= 1;
end
declare @notes int = rand()*3.00;
while @notes > 0
begin
insert into AppointmentNotes (AppointmentID, NoteID, Note)
values (@appointmentID, @notes, replicate ('Y', rand()*1000));
set @notes -= 1;
end
set @i += 1;
if @i % 10000 = 0
begin
commit;
raiserror (N'Added %i appointments...', 0, 1, @i);
begin transaction;
end
end
commit;
go
所以让我们看看今天几个人的约会：
set statistics time on;
set statistics io on;
declare @acl AccessControlList;
insert into @acl (PersonOrGroupID) values (102),(111),(131);
exec usp_getAppointmentsForACL @acl, '20100730', '20100731';
Table 'AppointmentNotes'. Scan count 8, logical reads 39, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Worktable'. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Appointments'. Scan count 1, logical reads 9829, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'AppointmentRoles'. Scan count 3, logical reads 96, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table '#25869641'. Scan count 1, logical reads 1, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
SQL Server Execution Times:
CPU time = 63 ms, elapsed time = 1294 ms.
SQL Server Execution Times:
CPU time = 63 ms, elapsed time = 1294 ms.
1.2 秒（在冷缓存上，它在热缓存上达到 224 毫秒）。嗯，这不是很好。问题是约会表中的 9829 页命中。为了改进这一点，我们希望同时拥有两个过滤条件（acl和日期）。也许是索引视图？
create view vwAppointmentAndRoles
with schemabinding
as
select r.PersonOrGroupID, a.AppointmentID, a.Start, a.[End]
from dbo.AppointmentRoles r
join dbo.Appointments a on r.AppointmentID = a.AppointmentID;
go
create unique clustered index cdxVwAppointmentAndRoles on vwAppointmentAndRoles (PersonOrGroupID, Start, [End]);
go
alter procedure usp_getAppointmentsForACL
@acl AccessControlList readonly,
@start datetime,
@end datetime
as
begin
set nocount on;
select ar.AppointmentID
, a.Location
, r.Role
, n.NoteID
, n.Note
from @acl l
join vwAppointmentAndRoles ar with (noexpand) on l.PersonOrGroupID = ar.PersonOrGroupID
join AppointmentNotes n on n.AppointmentID = ar.AppointMentID
join Appointments a on ar.AppointmentID = a.AppointmentID
join AppointmentRoles r
on ar.AppointmentID = r.AppointmentID
and ar.PersonOrGroupID = r.PersonOrGroupID
where ar.Start >= @start
and ar.Start <= @end
and ar.[End] <= @end;
end
go
我们还可以将 Appointments 上的聚集索引更改为可能更有用的 AppointmentID：
drop index cdxAppointmentStart on Appointments;
create clustered index cdxAppointmentAppointmentID on Appointments (AppointmentID);
go
这将在 77 毫秒内返回同一日期范围内同一 @acl 列表中的约会（在热缓存上）。
现在，当然，您应该使用的实际模式取决于更多未考虑的因素。但我希望这能让您对现在采取适当的行动以获得良好的性能有所了解。将表值参数添加到客户端执行上下文并将其传递给过程以及 LINQ 集成，留给读者作为练习。