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Cost threshold for parallelism
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Cost threshold for parallelism
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SQLSACT
SQLSACT
Posted Tuesday, November 27, 2012 3:45 AM
Ten Centuries
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Last Login: Today @ 8:22 AM
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Hi all
When dealing with the Cost threshold for parallelism, I am almost certain that the
Cost
is not an amount in seconds but rather a number that SQL Server internally uses.
Is this correct?
I'm asking because I am going through a well-known book and it says:
The "cost" is the estimated amount of time in seconds that it would take to execute
Is my understanding wrong?
Thanks
Post #1389057
s_osborne2
s_osborne2
Posted Tuesday, November 27, 2012 3:55 AM
SSChasing Mays
Group: General Forum Members
Last Login: Today @ 10:06 AM
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Hi,
I'm also of the understanding that "cost" is just an arbitrary no.
This
link
seems to back that up.
Thanks,
Simon
MCSA: SQL Server 2012
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Simon Osborne
Post #1389061
anthony.green
anthony.green
Posted Tuesday, November 27, 2012 3:56 AM
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From MSDN
The cost refers to an estimated elapsed time in seconds required to run the serial plan on a specific hardware configuration
http://msdn.microsoft.com/en-us/library/ms188603(v=SQL.105).aspx
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Post #1389064
SQLSACT
SQLSACT
Posted Tuesday, November 27, 2012 4:03 AM
Ten Centuries
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anthony.green (11/27/2012)
From MSDN
The cost refers to an estimated elapsed time in seconds required to run the serial plan on a specific hardware configuration
http://msdn.microsoft.com/en-us/library/ms188603(v=SQL.105).aspx
From SSC
http://www.sqlservercentral.com/Forums/Topic1287679-146-1.aspx#bm1287938
Post #1389069
anthony.green
anthony.green
Posted Tuesday, November 27, 2012 4:08 AM
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I stand corrected.
Want an answer fast? Try here
How to post data/code for the best help - Jeff Moden
Need a string splitter, try this - Jeff Moden
How to post performance problems - Gail Shaw
CrossTabs-Part1
&
Part2 - Jeff Moden
SQL Server Backup, Integrity Check, and Index and Statistics Maintenance - Ola Hallengren
Managing Transaction Logs - Gail Shaw
Troubleshooting SQL Server: A Guide for the Accidental DBA - Jonathan Kehayias and Ted Krueger
Post #1389070
SQLSACT
SQLSACT
Posted Tuesday, November 27, 2012 4:41 AM
Ten Centuries
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anthony.green (11/27/2012)
I stand corrected.
Can I assume that my documentation is incorrect then?
Post #1389087
anthony.green
anthony.green
Posted Tuesday, November 27, 2012 5:02 AM
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Yes I would as Gail has mentioned that the documentation on MSDN is incorrect, so anything which says its in seconds is incorrect.
Want an answer fast? Try here
How to post data/code for the best help - Jeff Moden
Need a string splitter, try this - Jeff Moden
How to post performance problems - Gail Shaw
CrossTabs-Part1
&
Part2 - Jeff Moden
SQL Server Backup, Integrity Check, and Index and Statistics Maintenance - Ola Hallengren
Managing Transaction Logs - Gail Shaw
Troubleshooting SQL Server: A Guide for the Accidental DBA - Jonathan Kehayias and Ted Krueger
Post #1389107
anthony.green
anthony.green
Posted Tuesday, November 27, 2012 5:04 AM
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Yes I would as Gail has mentioned that the documentation on MSDN is incorrect, so anything which says its in seconds is incorrect.
Want an answer fast? Try here
How to post data/code for the best help - Jeff Moden
Need a string splitter, try this - Jeff Moden
How to post performance problems - Gail Shaw
CrossTabs-Part1
&
Part2 - Jeff Moden
SQL Server Backup, Integrity Check, and Index and Statistics Maintenance - Ola Hallengren
Managing Transaction Logs - Gail Shaw
Troubleshooting SQL Server: A Guide for the Accidental DBA - Jonathan Kehayias and Ted Krueger
Post #1389108
GilaMonster
GilaMonster
Posted Tuesday, November 27, 2012 7:25 AM
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It's not seconds (anymore). It's a meaningless, unitless number.
It was originally based off of seconds on a specific benchmark machine back when the QO was initially developed, back sometime in the mid 90's
Gail Shaw
Microsoft Certified Master: SQL Server 2008, MVP
SQL In The Wild
: Discussions on DB performance with occasional diversions into recoverability
We walk in the dark places no others will enter
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Post #1389185
Grant Fritchey
Grant Fritchey
Posted Wednesday, November 28, 2012 8:04 AM
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Just remember that the number is an estimate. This means it can be wildly inaccurate. But, it's the only number you get, so you're going to use it, just don't rely on it.
----------------------------------------------------
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood..." Theodore Roosevelt
The Scary DBA
Author of:
SQL Server 2012 Query Performance Tuning
SQL Server 2008 Query Performance Tuning Distilled
and
SQL Server Execution Plans
Product Evangelist for
Red Gate Software
Post #1389812
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