Posted inSQL
Microsoft
13 years ago
Provide a hint to force generation of a parallel plan
The SQL Server query optimizer often chooses a serial plan (with a significant estimated cost) where a parallel plan would execute much faster. Often, the desired parallel plan costs only very slightly higher than the serial version.
Declined
Query Processing and Intelligent DatabaseSuggestionsDeclined
Company Response
Microsoft
Company Response
Up: 220<=-=Dec 21 2011 10:50AM=-=>Thanks for the suggestion. We will consider this for a future release. There is an undocumented trace flag 8649 to set the cost overhead of parallelism to 0. This may provide some relief, but is not a full solution. You can use it in a query hint in the form OPTION.Best regards,Eric HansonProgram MangerSQL Server Query Processing<=-=Dec 21 2011 3:39PM=-=>Hi Eric,Thanks for the very quick response. TF 8649 is indeed very helpful � perhaps we�re not so far away from seeing a PARALLEL_PLAN or MINDOP hint as I thought! Very cool, thanks again.Paul<=-=Feb 20 2014 1:02AM=-=>Any update on this? a normal hint would be much better than some undocumented or short term workarounds.<=-=Jun 8 2014 10:04PM=-=>Any update? It�s been a couple of years�.<=-=Dec 1 2014 1:26AM=-=>I have major problem with this, too. Any updates?<=-=Dec 16 2014 2:18PM=-=>Are there any plans at MS to go forward with this beautiful suggestion?<=-=May 26 2015 9:12AM=-=>There is an extremely strong use case for this with Columnstore indexes. I can show queries with an estimated cost of .7 that get a major performance boost by going from row mode to batch mode processing within the Columnstore index.<=-=Dec 20 2016 5:09PM=-=>Sadly, while OPTION works, it requires elevated privileges, or using it in a SP owned by SA� My testing shows it really helps, but I can�t incorporate it into our application due to the permissions issue.Please, PLEASE add a supported PARALLEL_PLAN query hint to a SQL2016 service pack!<=-=Dec 22 2016 6:32AM=-=>I have mixed feelings about this. I work with developers that look at query hints as the first answer not the last resort. NoLock, Index hints, Join hints, whatever magic they happen to read about that �solved� some particular problem.This would be a very sharp tool to put in the hands of even experienced developers.However, I d in favor.<=-=Mar 2 2017 5:50PM=-=>This will be addressed in an upcoming SQL Server 2016 SP..
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