Sql server 外键关系可能存在的性能问题

我们有一个

User

表，其中

GUID

aka

uniqueidentifier

作为

PK

。数据库中几乎所有其他表都使用4

FK

引用与此表关联。当我看

DB

图表时，它看起来像一条100车道的高速公路从

用户表中出来，因为
CreatedBy
，
CreatedByProxy
，
UpdatedBy
，
UpdatedBy
外键

我被带到这个项目是因为它已经过了初始阶段，并且已经投入生产，并且存在性能问题

我想知道，当用户列表开始增长时，这种
DB
模式是否会导致严重的成长问题。因此，我们将来会遇到更多的性能问题吗？或者，如果我们创建一个索引，保留外键会导致索引变得庞大吗。我只是不记得以前有一个网站有外键到这种程度，我担心将来的校对/修复。我只是想证明是否保留或删除外键，或者修改结构，以便

用户表：

    CREATE TABLE [dbo].[aspnet_Users](
        [ApplicationId] [uniqueidentifier] NOT NULL,
        [UserId] [uniqueidentifier] NOT NULL, -- ***** Here is the PK
        [UserName] [nvarchar](256) NOT NULL,
        [LoweredUserName] [nvarchar](256) NOT NULL,
        [MobileAlias] [nvarchar](16) NULL,
        [IsAnonymous] [bit] NOT NULL,
        [LastActivityDate] [datetime] NOT NULL,
    PRIMARY KEY NONCLUSTERED 
    (
        [UserId] ASC
    )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
    ) ON [PRIMARY]

CREATE TABLE [dbo].[Email](
    [EmailId] [int] IDENTITY(1,1) NOT NULL,
    [PersonId] [int] NULL,
    [InstitutionId] [int] NULL,
    [EmailTypeId] [int] NOT NULL,
    [EmailAddress] [varchar](254) NOT NULL,
    [IsFlaggedImportant] [bit] NOT NULL,
    [IsDistrictRecord] [bit] NOT NULL,
    [IsActive] [bit] NOT NULL,
    [Created] [datetime] NOT NULL,
    [CreatedBy] [uniqueidentifier] NOT NULL, -- ***** FK 1
    [Proxy] [uniqueidentifier] NULL, -- ***** FK 2
    [Updated] [datetime] NULL,
    [UpdatedBy] [uniqueidentifier] NULL, -- ***** FK 3
    [UpdateProxy] [uniqueidentifier] NULL, -- ***** FK 4
 CONSTRAINT [PK_Email] PRIMARY KEY CLUSTERED 
(
    [EmailId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

SET ANSI_PADDING OFF
GO

ALTER TABLE [dbo].[Email] ADD  CONSTRAINT [DF_Email_IsPrimary]  DEFAULT ((0)) FOR [IsFlaggedImportant]
GO

ALTER TABLE [dbo].[Email] ADD  CONSTRAINT [DF_Email_IsDistrictRecord]  DEFAULT ((0)) FOR [IsDistrictRecord]
GO

ALTER TABLE [dbo].[Email] ADD  CONSTRAINT [DF_Email_IsActive]  DEFAULT ((0)) FOR [IsActive]
GO

ALTER TABLE [dbo].[Email] ADD  CONSTRAINT [DF_Email_Created]  DEFAULT (getdate()) FOR [Created]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_CreatedByUser] FOREIGN KEY([CreatedBy])
REFERENCES [dbo].[aspnet_Users] ([UserId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_CreatedByUser]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_EmailType] FOREIGN KEY([EmailTypeId])
REFERENCES [dbo].[EmailType] ([EmailTypeId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_EmailType]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_Institution] FOREIGN KEY([InstitutionId])
REFERENCES [dbo].[Institution] ([InstitutionId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_Institution]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_Person] FOREIGN KEY([PersonId])
REFERENCES [dbo].[Person] ([PersonId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_Person]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_ProxyByUser] FOREIGN KEY([Proxy])
REFERENCES [dbo].[aspnet_Users] ([UserId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_ProxyByUser]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_ProxyUpdateByUser] FOREIGN KEY([UpdateProxy])
REFERENCES [dbo].[aspnet_Users] ([UserId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_ProxyUpdateByUser]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_UpdatedByUser] FOREIGN KEY([UpdatedBy])
REFERENCES [dbo].[aspnet_Users] ([UserId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_UpdatedByUser]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [CK_Email_Person_Or_Institution] CHECK  (([PersonId] IS NOT NULL AND [InstitutionId] IS NULL OR [PersonId] IS NULL AND [InstitutionId] IS NOT NULL))
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [CK_Email_Person_Or_Institution]
GO

另一个引用用户的表：

    CREATE TABLE [dbo].[aspnet_Users](
        [ApplicationId] [uniqueidentifier] NOT NULL,
        [UserId] [uniqueidentifier] NOT NULL, -- ***** Here is the PK
        [UserName] [nvarchar](256) NOT NULL,
        [LoweredUserName] [nvarchar](256) NOT NULL,
        [MobileAlias] [nvarchar](16) NULL,
        [IsAnonymous] [bit] NOT NULL,
        [LastActivityDate] [datetime] NOT NULL,
    PRIMARY KEY NONCLUSTERED 
    (
        [UserId] ASC
    )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
    ) ON [PRIMARY]

CREATE TABLE [dbo].[Email](
    [EmailId] [int] IDENTITY(1,1) NOT NULL,
    [PersonId] [int] NULL,
    [InstitutionId] [int] NULL,
    [EmailTypeId] [int] NOT NULL,
    [EmailAddress] [varchar](254) NOT NULL,
    [IsFlaggedImportant] [bit] NOT NULL,
    [IsDistrictRecord] [bit] NOT NULL,
    [IsActive] [bit] NOT NULL,
    [Created] [datetime] NOT NULL,
    [CreatedBy] [uniqueidentifier] NOT NULL, -- ***** FK 1
    [Proxy] [uniqueidentifier] NULL, -- ***** FK 2
    [Updated] [datetime] NULL,
    [UpdatedBy] [uniqueidentifier] NULL, -- ***** FK 3
    [UpdateProxy] [uniqueidentifier] NULL, -- ***** FK 4
 CONSTRAINT [PK_Email] PRIMARY KEY CLUSTERED 
(
    [EmailId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

SET ANSI_PADDING OFF
GO

ALTER TABLE [dbo].[Email] ADD  CONSTRAINT [DF_Email_IsPrimary]  DEFAULT ((0)) FOR [IsFlaggedImportant]
GO

ALTER TABLE [dbo].[Email] ADD  CONSTRAINT [DF_Email_IsDistrictRecord]  DEFAULT ((0)) FOR [IsDistrictRecord]
GO

ALTER TABLE [dbo].[Email] ADD  CONSTRAINT [DF_Email_IsActive]  DEFAULT ((0)) FOR [IsActive]
GO

ALTER TABLE [dbo].[Email] ADD  CONSTRAINT [DF_Email_Created]  DEFAULT (getdate()) FOR [Created]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_CreatedByUser] FOREIGN KEY([CreatedBy])
REFERENCES [dbo].[aspnet_Users] ([UserId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_CreatedByUser]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_EmailType] FOREIGN KEY([EmailTypeId])
REFERENCES [dbo].[EmailType] ([EmailTypeId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_EmailType]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_Institution] FOREIGN KEY([InstitutionId])
REFERENCES [dbo].[Institution] ([InstitutionId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_Institution]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_Person] FOREIGN KEY([PersonId])
REFERENCES [dbo].[Person] ([PersonId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_Person]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_ProxyByUser] FOREIGN KEY([Proxy])
REFERENCES [dbo].[aspnet_Users] ([UserId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_ProxyByUser]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_ProxyUpdateByUser] FOREIGN KEY([UpdateProxy])
REFERENCES [dbo].[aspnet_Users] ([UserId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_ProxyUpdateByUser]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [FK_Email_UpdatedByUser] FOREIGN KEY([UpdatedBy])
REFERENCES [dbo].[aspnet_Users] ([UserId])
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [FK_Email_UpdatedByUser]
GO

ALTER TABLE [dbo].[Email]  WITH CHECK ADD  CONSTRAINT [CK_Email_Person_Or_Institution] CHECK  (([PersonId] IS NOT NULL AND [InstitutionId] IS NULL OR [PersonId] IS NULL AND [InstitutionId] IS NOT NULL))
GO

ALTER TABLE [dbo].[Email] CHECK CONSTRAINT [CK_Email_Person_Or_Institution]
GO

我被带到这个项目是因为它已经过了初始阶段
并且已经投入生产，并且存在性能问题

您没有说明这些性能问题是什么，因此我将仅限于外键

当我看DB图时，它看起来像一条100车道的高速公路
由于CreatedBy、CreatedByProxy、，
UpdatedBy，UpdatedBy代理外键

当我看到这样的列时，我必须询问它们是否包含关于业务实体的信息——在本例中是一个人的电子邮件地址——或者关于该实体所在行的信息

它们似乎包含有关该行的信息。（但我可能错了。）

如果它们确实包含关于行的信息，并且在大多数查询中不需要它们，则可以将它们移动到另一个表中。如果移动它们，则在将行插入dbo.Email时必须更加小心

CREATE TABLE [dbo].[Email](
    [EmailId] [int] IDENTITY(1,1) NOT NULL,
    [PersonId] [int] NULL,
    [InstitutionId] [int] NULL,
    [EmailTypeId] [int] NOT NULL,
    [EmailAddress] [varchar](254) NOT NULL,
    [IsFlaggedImportant] [bit] NOT NULL,
    [IsDistrictRecord] [bit] NOT NULL,
    [IsActive] [bit] NOT NULL,
    CONSTRAINT [PK_Email] PRIMARY KEY CLUSTERED ([EmailID])
);

CREATE TABLE [dbo].[Email_audit](
    [EmailID] [int] PRIMARY KEY REFERENCES [Email] ([EmailID]),
    [Created] [datetime] NOT NULL,
    [CreatedBy] [uniqueidentifier] NOT NULL, -- ***** FK 1
    [Proxy] [uniqueidentifier] NULL,         -- ***** FK 2
    [Updated] [datetime] NULL,
    [UpdatedBy] [uniqueidentifier] NULL,     -- ***** FK 3
    [UpdateProxy] [uniqueidentifier] NULL    -- ***** FK 4
);

这类表通常用于提供某种审计跟踪。是否可以级联删除取决于应用程序。在某些应用程序中，您需要在此处存储电子邮件地址而不是电子邮件id号，并且不使用外键引用。（这允许从dbo.Email中删除行，同时保留有关行发生了什么的一些信息。）

移动这些列可以将dbo.Email中的行宽度减少约80字节，而不计算开销。这通常会提高从中移动SELECT语句的表中SELECT语句的性能。（行数越窄；每页行数越多。）

但是，移动这些列会使插入和更新行变得复杂。所有的插入和更新都必须命中两个表。
在
GUID
列上使用集群主键肯定会破坏性能。这将导致大量索引碎片，并可能导致操作中出现大量页面拆分，从而导致最终性能损失，但OP没有在GUID上创建群集主键。OP在一个表中的GUID上有一个非聚集主键，在另一个表中的电子邮件上有一个聚集主键。