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Rob Farley

- Owner/Principal with LobsterPot Solutions (a MS Gold Partner consulting firm), Microsoft Certified Master, Microsoft MVP (SQL Server), and leader of the SQL User Group in Adelaide, Australia. Rob is a former director of PASS, and provides consulting and training courses around the world in SQL Server and BI topics.

T-SQL Tuesday - Query Cost

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Published Tuesday, March 9, 2010 11:03 AM by Rob Farley



AaronBertrand said:

Bummer!  I was going to do a "Bad habits to kick : ignoring I/O" post for tomorrow, but my ideas were pretty much identical to yours.  Kudos.

March 8, 2010 6:38 PM

Rob Farley said:

You should still write it though.

March 8, 2010 6:51 PM

Armando Prato said:

I'd give SET STATISTICS TIME ON a shout out too.  I've found my own fair share of instances where a query that appears to run acceptably time-wise and I/O wise may be over utilizing CPU.

March 8, 2010 10:52 PM

AaronBertrand said:

Yup, you're really right.  I abandoned my original idea though, and published a more broad "bad habits" type of I/O post.

March 8, 2010 10:59 PM

Mladen Prajdic said:

I'd run profiler to get the correct reads for your second method.

i've seen STATS IO get totally screwed up when doing string manipulations.

i have a query where the STATS IO show 30k reads while profiler shows 500k reads.

March 9, 2010 6:16 AM

Rob Farley said:

Yes, I demonstrated that in my talk, where a Compute Scalar had lots of hidden reads. stats io showed just 2 reads, when there were many in Profiler.

But the problem with this query is the intense CPU needed. There are some hidden I/O costs, but that's a small impact compared to the CPU.

March 9, 2010 7:12 AM
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