Wanted: Forced Parallelism

James Anderson would like a query hint to force parallelism:

I would like to see a hint that causes the optimiser to consider a parallel plan no matter the cost of the query. It’s possible to get this behaviour with trace flag 8649 but it’s unsupported by Microsoft and therefore unfit for production use.

I only tend to use query hints as a very last resort. It’s almost always better to allow the optimiser to make these decisions and continue to reevaluate these decisions as your data changes but sometimes they can be a get out of jail free card.

I’ve written about this before and so has Paul White. Paul created this connect item for something similar. Please vote it up if you think it could help with your query tuning.

Click through for the full argument, and then hit the Connect item if you agree.

Related Posts

Choosing Between Merge Join and Hash Join

Erik Darling gives us a Sophie’s Choice: It could have chosen a Hash Join, but then the order of the Id column from the Posts table wouldn’t have been preserved on the other side. Merge Joins are order preserving, Hash Joins aren’t. If we use a Hash Join, we’re looking at ordering the results of […]

Read More

Puzzling Through Older Problems

Kenneth Fisher shares a couple of interview puzzles: The year is 2004. You’re taking a tech test as an interview for a SQL development job. They have a page in their application that displays up to 20 rows of information. They need a piece of code that will return the rows from a given page. […]

Read More

Categories

January 2017
MTWTFSS
« Dec Feb »
 1
2345678
9101112131415
16171819202122
23242526272829
3031