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The Scary DBA

I have twenty+ years experience in IT. That time was spent in technical support, development and database administration. I work forRed Gate Software as a Product Evangelist. I write articles for publication at SQL Server Central, Simple-Talk, PASS Book Reviews and SQL Server Standard. I have published two books, ”Understanding SQL Server Execution Plans” and “SQL Server 2008 Query Performance Tuning Distilled.” I’m one of the founding officers of the Southern New England SQL Server Users Group and its current president. I also work on part-time, short-term, off-site consulting contracts. In 2009 and 2010 I was awarded as a Microsoft SQL Server MVP. In the past I’ve been called rough, intimidating and scary. To which I usually reply, “Good.” You can contact me through grant -at- scarydba dot kom (unobfuscate as necessary).

The Utility of Execution Plans in Natively Compiled Procedures

I’m actually having problems identifying the utility of execution plans when working with natively compiled procedures. Or, put another way, why bother? I’ve posted a couple of times on natively compiled procedures and SQL Server execution plans. I’ve found the differences interesting and enlightening, but I’m seriously questioning why I should bother, at least currently. I’m sure there will be many changes to the behaviors of the natively compiled procedures and their relationship with execution plans. But right now, well, let’s look at an example. I have three simple tables stored in-memory. Here’s the definition of one:

CREATE TABLE dbo.Address
    (
     AddressID INT IDENTITY(1, 1)
                   NOT NULL
                   PRIMARY KEY NONCLUSTERED HASH WITH (BUCKET_COUNT = 50000),
     AddressLine1 NVARCHAR(60) NOT NULL,
     AddressLine2 NVARCHAR(60) NULL,
     City NVARCHAR(30) COLLATE Latin1_General_100_BIN2 NOT NULL,
     StateProvinceID INT NOT NULL,
     PostalCode NVARCHAR(15) NOT NULL,
     ModifiedDate DATETIME
        NOT NULL
        CONSTRAINT DF_Address_ModifiedDate DEFAULT (GETDATE())
    )
    WITH (
         MEMORY_OPTIMIZED=
         ON);

I can then create the following code as a natively compiled procedure:

CREATE PROC [dbo].[AddressDetails] @City NVARCHAR(30)
    WITH NATIVE_COMPILATION,
         SCHEMABINDING,
         EXECUTE AS OWNER
AS
    BEGIN ATOMIC
WITH (TRANSACTION ISOLATION LEVEL = SNAPSHOT, LANGUAGE = N'us_english')
        SELECT  a.AddressLine1,
                a.City,
                a.PostalCode,
                sp.Name AS StateProvinceName,
                cr.Name AS CountryName
        FROM    dbo.Address AS a
                JOIN dbo.StateProvince AS sp
                ON sp.StateProvinceID = a.StateProvinceID
                JOIN dbo.CountryRegion AS cr
                ON cr.CountryRegionCode = sp.CountryRegionCode
        WHERE   a.City = @City;
    END
GO

When I call for an estimated plan (remember, no actual plans) I’ll get this:

Scan

If you click on it, you’ll note that there’s an index scan. But the costs are all zero. Everything is FREE! Or not. The execution time is 93ms. If I put an index on the City column, the execution plan changes to the one I showed previously, an index seek, and the execution time goes to 42ms. Clearly, the scans are costing something. Scans aren’t necessarily bad and seeks aren’t necessarily good, but it’s hard to spot issues with execution plans with no costing involved at all. Which makes me wonder, should we bothering with execution plans for the natively compiled procs? I’m honestly unsure.

For most query tuning, statistics matter a lot. I understand we still have room in Albany on July 25th. You can register here. I’m doing an all day session at SQL Connections in September in Las Vegas. Go here to register for this great event. In Belgium in October, I’ll be doing an all day session on execution plans at SQL Server Days. Go here to register for this event. I’d love to talk query tuning with you all day long.

 

 

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