Reserved Memory Allocation Waits And Trace Flag 834

Joe Obbish has another post looking at sub-optimal columnstore index performance:

It is possible to see a scalability bottleneck in the form of high average wait time for the RESERVED_MEMORY_ALLOCATION_EXT wait if a highly concurrent workload is run on a server that consumes memory with batch mode operators. I believe that the severity of the bottleneck depends on unknown factors in the server’s initial memory state and the rate of memory actually used by queries to run batch mode operations. This blog post shares a reproduction of the issue along with a call to action.

If you use clustered columnstore indexes, check out Joe’s User Voice entry.

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Preventing Issues With Columnstore Indexes

Kevin Chant has a post covering issues in his experience with the creation of columnstore indexes: Error due to online statement It’s a very common error caused usually by somebody copying a rowstore “Create Index” command. The “online=on” option you use with rowstore indexes does not work with creating columnstore indexes yet. For the record the […]

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Avoid Key Lookups On Clustered Columnstore Indexes

Joey D’Antoni points out a potential big performance problem with clustered columnstore indexes: In the last year or so, with a large customer who makes fairly heavy use of this pattern, I’ve noticed another concern. Sometimes, and I can’t figure out what exactly triggers it, the execution plan generated, will do a seek against the […]

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