SQL Server 2005和Hibernate使用索引时出现问题

我对Hibernate生成的不使用索引的查询有问题。使用JTDS从Java访问数据库,服务器版本为SQL server ,最新的服务包。

还可以使用带有以下SQL代码的标准查询分析器来验证这种情况:

创建表和索引

CREATE TABLE [dbo].[TestNulls](
    [PK] [varchar](36) NOT NULL,
    [DATA] [varchar](36) NULL,
    [DATANULL] [varchar](36) NULL,
 CONSTRAINT [PK_TestNulls] PRIMARY KEY NONCLUSTERED
(
[PK] 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 NONCLUSTERED INDEX [IDX_DATA] ON [dbo].[TestNulls]
(
[DATA] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, 
IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, 
ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO

CREATE NONCLUSTERED INDEX [IDX_DATANULL] ON [dbo].[TestNulls]
(
[DATANULL] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, 
IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON,     
ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO

declare @i as int
set @i = 0
while (@i < 500000)
begin
  set nocount on

  insert into TestNulls values(NEWID(), NEWID(), null)
  insert into TestNulls values(NEWID(), null, null)
  insert into TestNulls values(NEWID(), null, null)           
  set @i = (@i + 1)
  set nocount on
end;

此查询将执行完整的表扫描

declare @p varchar(36)
set @p = NEWID()
select PK, DATA, DATANULL from TestNulls
where DATANULL = @p

所需帮助:

• 如何强制JTDS/Hibernate组合使用索引(SendStringParametersUnicode在默认情况下已设置为false)?
• 对这种行为有什么解释吗?

马西莫