Why Sql Indexed View always use Clustered Index - sql-server-2005

Question

I need some pointer on how to debug the following problem.
Environment: SQL Server 2005 Enterprise.
I have an indexed view with contains clustered index and multiple non-unique, non-clustered index. However when I execute the query, SQL server always perform Clustered index scan instead of index seek on my key.
Here is a simplify version.
CREATE VIEW MyIndexedView WITH SCHEMABINDING
SELECT a.Col1, b.Col2, c.Col3, d.Col4
FROM a JOIN b on a.id = b.id
JOIN c on a.id = c.id
JION d on c.id = d.id
There is a clustered index on Col1, and non-unique, non-clustered on Col2, Col3.
When I run the following query
SELECT a.Col1, b.Col2, c.Col3 FROM MyIndexedView WITH(NOEXPAND) WHERE b.Col2='blah'
and look at execution plan, I see SQL server run Clustered index scan on a.Col1 instead of perform index seek on Col2.
I tried to recreate the view and index.
Updated:
I did some additional testing and running these two queries side by side in Query Analyzer.
a) SELECT a.Col1, b.Col2, c.Col3
FROM MyIndexedView WITH(NOEXPAND) WHERE b.Col2='blah'
b) SELECT a.Col1, b.Col2, c.Col3
FROM MyIndexedView WHERE b.Col2 = 'blah'
Query 'a' will take 95% of the time and use Cluster Indexed scan. Query 'b' will only take 5% of the time and use Index Seek on col2. I try to swap the order of queries (run b first and a later) yield the same percentage.
This little experiment confirm that if sql use index seek it will be faster then cluster index scan.
Second I though if I don't include "WITH(NOEXPAND)" then SQL server will not use index on Indexed view. (Maybe I should start another question on the exact step to create indexed view).

Answer 1

I reproduced your sample and came up with the expected results with the index seek on Col2. The only way I was able to get it to do the clustered index scan was if I disabled the index. So first try rebuilding the index on Col2 to make sure it is actually enabled (or check the "Use Index" checkbox in index properties - options).
Here are the scripts I used to create the tables, view & indexes
CREATE TABLE [dbo].[a](
[id] [int] IDENTITY(1,1) NOT NULL,
[Col1] [varchar](100) NOT NULL,
CONSTRAINT [PK_a] PRIMARY KEY CLUSTERED
(
[id] 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
CREATE TABLE [dbo].[b](
[id] [int] IDENTITY(1,1) NOT NULL,
[Col2] [varchar](100) NOT NULL,
CONSTRAINT [PK_b] PRIMARY KEY CLUSTERED
(
[id] 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
CREATE TABLE [dbo].[c](
[id] [int] IDENTITY(1,1) NOT NULL,
[Col3] [varchar](100) NOT NULL,
CONSTRAINT [PK_c] PRIMARY KEY CLUSTERED
(
[id] 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
CREATE TABLE [dbo].[d](
[id] [int] IDENTITY(1,1) NOT NULL,
[Col4] [varchar](100) NOT NULL,
CONSTRAINT [PK_d] PRIMARY KEY CLUSTERED
(
[id] 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
CREATE VIEW [dbo].[MyIndexedView] WITH SCHEMABINDING
AS
SELECT a.Col1, b.Col2, c.Col3, d.Col4
FROM dbo.a JOIN dbo.b on a.id = b.id
JOIN dbo.c on a.id = c.id
JOIN dbo.d on c.id = d.id
GO
/****** Object: Index [IX] Script Date: 11/13/2009 21:50:01 ******/
CREATE UNIQUE CLUSTERED INDEX [IX] ON [dbo].[MyIndexedView]
(
[Col1] 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
/****** Object: Index [IX2] Script Date: 11/13/2009 21:50:39 ******/
CREATE NONCLUSTERED INDEX [IX2] ON [dbo].[MyIndexedView]
(
[Col2] ASC,
[Col3] 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
And I populated the tables like this:
declare #x int
SET #x = 0
while #x < 10
begin
INSERT INTO a (Col1 ) VALUES (newid())
INSERT INTO b (Col2 ) VALUES (newid())
INSERT INTO c (Col3 ) VALUES (newid())
INSERT INTO d (Col4 ) VALUES (newid())
SET #x=#x+1
end
Executing your query
SELECT Col1, Col2, Col3 FROM MyIndexedView WITH(NOEXPAND) WHERE Col2='blah'
shows an index seek on IX2
but if I disable that index
ALTER INDEX [IX2] ON [dbo].[MyIndexedView] DISABLE
and rerun, I see the clustered index scan on MyIndexedView.IX

Answer 2

How many records are there in your view?
If the result of the join is small then it is most cost efficient to scan the clustered index than seek another.