Execution Plan Incomplete

Question

Execution Plan Incomplete

Tom Uellner

SSCrazy

Points: 2995
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July 16, 2013 at 4:06 pm

#275279

I'm trying to show a developer how to rewrite a stored procedure. It's a pretty scary SP (hundreds of lines of T-SQL in a cursor loop doing a bunch of selects - all to create a dynamic SQL statement). I know we're all cringing in horror at this point but what I wanted to do was show him just how bad the performance would be and what it would do to SQL Server by walking him through the execution plan. When I include the actual execution plan, the SP that normally runs about 6 - 10 seconds now runs for over a minute (which I presume is the time spent generating the plan). The problem comes from the plan not finishing. I scrolled through this and when I got to the end of the plan screen, it was cut off half way through a query.
The question is - Is there a way to display the entire plan? Any switches or tricks for getting the entire plan to display?
Thanks
Tom

Viewing 6 posts - 1 through 5 (of 5 total)

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Erland Sommarskog SSC-Insane Points: 24038 More actions · Answer 1

Why on Earth would you want to see the execution plan for that horrible procedure? When you have a loop, there will be plan for execution of a statement, and SSMS is likely to choke. (Which is one reason why it taking such long time to run. There is an overhead for creating the XML as well.)

If you want to show the developer how bad the procedeure is, the current behaviour does serve as threating example, but I'm not sure that the developer will get the drift anyway.

[font="Times New Roman"]Erland Sommarskog, SQL Server MVP, www.sommarskog.se[/font]

Gail Shaw SSC Guru Points: 1004504 More actions · Answer 2

TUellner (7/16/2013)
(which I presume is the time spent generating the plan).

That's the time spend by SSMS rendering the plan, before it runs out of memory (or hits max resultsets) and gives up.

There's no good reason to display a plan of a procedure like that, you can't really demonstrate much from a plan of a cursor, just lots and lots and lots of repetition of the same piece of the plan.

Maybe use performance characteristics to teach this lesson and show him exec plans of something simpler?

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

Tom Uellner SSCrazy Points: 2995 More actions · Answer 3

Thanks all. I know it's not useful for anything other than a teaching tool. I was hoping to get to the execution of the dynamic SQL mess at the end just out of savage curiosity.

-Tom

HowardW One Orange Chip Points: 29109 More actions · Answer 4

TUellner (7/16/2013)
Thanks all. I know it's not useful for anything other than a teaching tool. I was hoping to get to the execution of the dynamic SQL mess at the end just out of savage curiosity.
-Tom

Well that's a lot easier. Just change the exec/sp_executesql at the bottom of the SQL to a print, run the loop without generating plans and copy the SQL at the bottom to run in isolation.

Tom Uellner SSCrazy Points: 2995 More actions · Answer 5

Thanks Howard. I should have thought of that. Appreciate the help.