Stored Procuders which has multiple execution plans

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Stored Procuders which has multiple execution plans

vijay.singh 97987

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Points: 495
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November 16, 2010 at 2:41 am

#157317

Hi All,
I have few doubts on execution plans.
1) How to find the Stored Procuders which has/Generates multiple execution plans?
2) How to avoid the generation of multiple execution plans by SP's.
Please help me on this guys..:-)
Thanks in advance.
Regards,
Vijay Singh

Viewing 9 posts - 1 through 8 (of 8 total)

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ps. One Orange Chip Points: 29422 More actions · Answer 1

by default query processor generates multiple execution plan for any query that you submit and chooses one of them based on least cost. This is by design and you cannot control it. There are some cases where in if query processor determines that choosing amongst various execution plan is going to take more time, it generates one plan and executes the query as per that plan.

you can click on include actual execution plan to see what is the plan selected by the query processor.

Pradeep Singh

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

The only way you'll have multiple plans per procedure is if the procedure has been run with different SET options. Certain set options (see BoL for details) change the way the query must be executed and hence get a different 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

vijay.singh 97987 SSC-Addicted Points: 495 More actions · Answer 3

Thanks for the updates..:-)

When i saw the Cache i got SPs with multiple cache plan even after not changing the SET options.

Is there any other way to avoid this?

Thanks,

Vijay Singh

ps. One Orange Chip Points: 29422 More actions · Answer 4

what query are you running to see that?

Pradeep Singh

vijay.singh 97987 SSC-Addicted Points: 495 More actions · Answer 5

Hi Pradeep,

Below is the query :

SELECT db_name(st.dbid) DBName,

object_schema_name(st.objectid, dbid) SchemaName,

object_name(st.objectid, dbid) StoredProcedure,

MAX(cp.usecounts) Execution_count,

st.text [Plan_Text]

FROM sys.dm_exec_cached_plans cp

CROSS APPLY sys.dm_exec_sql_text(cp.plan_handle) st

WHERE db_name(st.dbid) IS NOT NULL

AND cp.objtype = 'proc'

GROUP BY cp.plan_handle,

db_name(st.dbid),

object_schema_name(objectid, st.dbid),

object_name(objectid, st.dbid),

st.text

ORDER BY MAX(cp.usecounts) DESC

Thanks,

Vijay Singh

ps. One Orange Chip Points: 29422 More actions · Answer 6

In some cases, query processor may keep two plans, 1) without using parallelism, 2) using parallism and use either of them.

beyond that, i cant think why you are seeing several plans for one sp.

Pradeep Singh

Gail Shaw SSC Guru Points: 1004504 More actions · Answer 7

ps. (11/16/2010)
In some cases, query processor may keep two plans, 1) without using parallelism, 2) using parallism and use either of them.

Nope. Recently debunked by Paul White (I'll leave it to him to come up with url, I'm working on a freshly installed machine)

If there are multiple plans (ie with different plan handles) then either set options are different or (user is different and query is not safe for reuse between different users)

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

ps. One Orange Chip Points: 29422 More actions · Answer 8

Yes i have that URL. He explained that a parallel plan can also be executed by a single processor.

http://sqlblog.com/blogs/paul_white/default.aspx%5B/url%5D

Pradeep Singh