为什么索引视图不会改善性能？

Question

I am testing the performance of an indexed view. Below are the codes that I used. I am using AdventureWorks2012 Database.

--Create test tables

 SELECT * 
    INTO Person.Person_Test
    FROM [Person].[Person]
    go
    SELECT * 
    INTO Person.PersonPhone_Test
    FROM [Person].[PersonPhone]
    go
    SELECT * 
    INTO Person.BusinessEntityAddress_Test
    FROM [Person].BusinessEntityAddress
    go
    SELECT * 
    INTO Person.Address_Test
    FROM [Person].Address
    go

SET STATISTICS IO ON
SET STATISTICS TIME ON

--Create indexes on tables

CREATE CLUSTERED INDEX Person1 ON Person.Person_Test (BusinessEntityID);
CREATE CLUSTERED INDEX PersonPhone1 ON Person.PersonPhone_Test (BusinessEntityID);
CREATE CLUSTERED INDEX BusEntity1 ON Person.BusinessEntityAddress_Test (BusinessEntityID);
CREATE INDEX BusEntity2 ON Person.BusinessEntityAddress_Test (AddressId);
CREATE CLUSTERED INDEX AddressInd1 ON Person.Address_Test (AddressId);

--Create a view based on the four tables

 CREATE VIEW My_View WITH SCHEMABINDING AS
      SELECT P.BusinessEntityID,P.FirstName,P.LastName, PH.PhoneNumber,PH.PhoneNumberTypeID,BU.AddressID,AD.AddressLine1
      FROM Person.Person_Test P
      INNER JOIN Person.PersonPhone_Test PH
      ON P.BusinessEntityID=PH.BusinessEntityID
      INNER JOIN Person.BusinessEntityAddress_Test BU
      ON P.BusinessEntityID=BU.BusinessEntityID
      INNER JOIN Person.Address_Test AD
      ON BU.AddressID=AD.AddressID
      WHERE P.BusinessEntityID BETWEEN 50 AND 10000 AND AD.AddressID BETWEEN 100 AND 1000
    GO

Then I test the performance without index (Query1)

--Test regular view 
SELECT BusinessEntityID,LastName,PhoneNumber,AddressID, AddressLine1
FROM My_View
WHERE BusinessEntityID between 50 and 200

The message I got is :

SQL Server parse and compile time: 
   CPU time = 0 ms, elapsed time = 8 ms.
SQL Server parse and compile time: 
   CPU time = 0 ms, elapsed time = 0 ms.

(91 row(s) affected)
Table 'Address_Test'. Scan count 91, logical reads 185, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'PersonPhone_Test'. Scan count 91, logical reads 184, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'Person_Test'. Scan count 91, logical reads 286, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'BusinessEntityAddress_Test'. Scan count 1, logical reads 3, 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 = 0 ms,  elapsed time = 1 ms.

Then I add index on the view

CREATE UNIQUE CLUSTERED INDEX idx_MyView ON My_View(BusinessEntityID);
go

However, I got the same message if I rerun the above Query 1. I also attach the Execution plan here. Both the Execution plans are the same, no matter the view is indexed or not indexed.

Is there something that I missed? Why the performance is the same after I add index to the view?

Answer 1

The view condition is more restrictive than the query condition. The view has less data than required.

WHERE P.BusinessEntityID BETWEEN 50 AND 10000 AND AD.AddressID BETWEEN 100 AND 1000

vs.

WHERE BusinessEntityID between 50 and 200

Even when that is fixed indexed view matching is very fragile and can fail. You might need to force it using NOEXPAND .

Answer 2

Thanks to @mxix . NOEXPAND gives me a new message.

SELECT BusinessEntityID,LastName,PhoneNumber,AddressID, AddressLine1
FROM My_View WITH (NOEXPAND)
WHERE BusinessEntityID between 50 and 200;
go

The message:

 SQL Server parse and compile time: 
       CPU time = 0 ms, elapsed time = 0 ms.
    SQL Server parse and compile time: 
       CPU time = 0 ms, elapsed time = 0 ms.

(91 row(s) affected)
Table 'My_View'. Scan count 1, logical reads 4, 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 = 0 ms,  elapsed time = 0 ms.

@FLICKER is also right that optimizer is very smart.

---

@usr points out the key point. If I use

SELECT BusinessEntityID,LastName,PhoneNumber,AddressID, AddressLine1
FROM My_View 
WHERE BusinessEntityID between 100 and 20000;
go

I don't need to specify NOEXPAND. SQL Server will use the index in view automatically.

SQL Server parse and compile time: 
   CPU time = 15 ms, elapsed time = 16 ms.
SQL Server parse and compile time: 
   CPU time = 0 ms, elapsed time = 0 ms.

(129 row(s) affected)
Table 'My_View'. Scan count 1, logical reads 5, 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 = 0 ms,  elapsed time = 0 ms.