Posted by Hugo Kornelis on 01/04/07 22:16

On 4 Jan 2007 07:12:58 -0800, kmounkhaty@yahoo.com wrote:

>Hi Guru,
>
>When I ran my adhoc script below it generated only 45000 reads or 4
>seconds but when I wrapped it into procedure it took about two minutes
>or millions of reads. The parameters calling both adhoc and proc are
>indeed the same. I'm pretty 99.9% sure that the proc does not recompile
>because I don't mix up between DDL and DML, no temp tables or any thing
>to cause proc to recompile. The big difference is adhoc used index scan
>for 45% but proc used bookmark lookup for 75%. Why it's so difference
>since they both returned the same results?
>
>Please help...

Hi Silaphet,

You might suffer from parameter sniffing. Google for this term to find
out what it is and how you can try to deal with it.

You should also consider creating three procedures for the three
versions of the SELECT statement, and change your current stored proc
into a simple IF ELSE tree to call either one of them. This way, each
stored proc can get an execution plan that is otimized for its
parameters.

--
Hugo Kornelis, SQL Server MVP
My SQL Server blog: http://sqlblog.com/blogs/hugo_kornelis

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