Do you advise to apply Recomendations given by DTA?

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Do you advise to apply Recomendations given by DTA?

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Gail Shaw SSC Guru Points: 1004504 More actions · Answer 1

Jeff Moden (8/22/2010)
I'm pretty sure that statistics TIME and IO don't include SQLCLR and I believe they sometimes miss what's happening in UDF's that a query may contain.

Correct on the UDF, least for the Stats IO, I don't know about the CLR

I'll have to double check and see if I can come up with an actual example,

Let me...

http://sqlinthewild.co.za/index.php/2009/04/29/functions-io-statistics-and-the-execution-plan/

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

We walk in the dark places no others will enter
We stand on the bridge and no one may pass

Ninja's_RGR'us SSC Guru Points: 294069 More actions · Answer 2

GilaMonster (8/23/2010)
Jeff Moden (8/22/2010)
I'm pretty sure that statistics TIME and IO don't include SQLCLR and I believe they sometimes miss what's happening in UDF's that a query may contain.
Correct on the UDF, least for the Stats IO, I don't know about the CLR
I'll have to double check and see if I can come up with an actual example,
Let me...
http://sqlinthewild.co.za/index.php/2009/04/29/functions-io-statistics-and-the-execution-plan/

Sorry but I don't trust that source, not official MS :-P:hehe:.

Jeff Moden SSC Guru Points: 1004414 More actions · Answer 3

GilaMonster (8/23/2010)
Jeff Moden (8/22/2010)
I'm pretty sure that statistics TIME and IO don't include SQLCLR and I believe they sometimes miss what's happening in UDF's that a query may contain.
Correct on the UDF, least for the Stats IO, I don't know about the CLR
I'll have to double check and see if I can come up with an actual example,
Let me...
http://sqlinthewild.co.za/index.php/2009/04/29/functions-io-statistics-and-the-execution-plan/

That's what I really like about your blogs... they have code that you can test to verify. Thanks, Gail and great blog on execution-plan "lies".

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

Rick.Cornell.SME SSCrazy Eights Points: 8597 More actions · Answer 4

I also agree with Gail and again test everything throughly before applying DTA recommendations. I have only use the ones with significant improvements in the past!