It's a computed column processing bug?

Hello everybody!

I have question about indexed and not indexed Persisted columns on sql server 2005. It's a bug?

First?, my version of SQL Server is

Microsoft SQL Server 2005 - 9.00.3186.00 (Intel X86) Aug 11 2007 03:13:58 Copyright (c) 1988-2005 Microsoft Corporation Developer Edition on Windows NT 5.1 (Build 2600: Service Pack 2)

Now I create two tables and try four select queries:

Code Snippet

SET ANSI_NULLS ON

SET ANSI_PADDING ON

SET ANSI_WARNINGS ON

SET ARITHABORT ON

SET CONCAT_NULL_YIELDS_NULL ON

SET NUMERIC_ROUNDABORT OFF

SET QUOTED_IDENTIFIER ON

GO

create table t1 (id int primary key, id_bigint as cast(id as bigint))

GO

create table t2 (id int primary key, id_bigint as cast(id as bigint) persisted)

GO

select * from t1 -- (1)

-- Clustered index scan with two times Compute Scalar

GO

select * from t2 -- (2)

-- Clustered index scan with one times Compute Scalar

GO

create index IX_t2 on t2 (id_bigint)

GO

select * from t2 -- (3)

-- Index Scan with one times Compute Scalar

GO

select * from t2 where id_bigint = 0 -- (4)

-- Index Seek with one times Compute Scalar

GO

drop table t1

GO

drop table t2

GO

SET ANSI_PADDING OFF

1. I don't understand why access to computed column raise scalar computation wto times?

2. I don't understand why access to persisted computed column raise any scalar computation?

3. I don't understand why access to persisted computed column over index required any scalar computations?

Can anyone from Microsoft SQL Server Team told me about this mistake?

It's a BUG or I incorrect understand value of the "PERSISTED" word?

--

Thanks with avanced.

WBR, Roman S. Golubin

grominc[at]gmail.com

Bug request on SQL Server 2005 Feedback for this icident.

To solve this problem while Microsoft SQL Server Team not fix this bug, use update with triggers instead persisted computed columns.

--

WBR, Roman S. Golubin

73! GL! RA1OGE/3

|||

It works.

Use 'WITH SCHEMABINDING'

Courtesy of Kent Tegels!