Clustered Columnstore Index Memory Timeouts

Joe Obbish takes a deep look at a clustered columnstore index insertion scenario:

Why should we care about memory grant timeouts for CCI insert queries? Simply put, lots of bad things can happen when those queries can time out, both for serial and for parallel inserts. For serial insert queries, I’ve observed deadlocks, extremely poor performance along with long SLEEP_TASK waits, and extremely long rollbacks. For parallel insert queries, I’ve observed queries that run seemingly forever, poor performance of the SELECT part, and error 8645. You probably don’t want any of that occurring in production. It would be very helpful if it was possible to extend the 25 second time-out for queries that insert into columnstore tables.

Read through as Joe learns the true meaning of Christmas a KB article.

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Errors Updating Stats on Columnstore Indexes

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Triggering KB 4462481

Joe Obbish shows how you can recreate the error described in KB 4462481: Consider a query execution that meets all of the following criteria: 1. A parallel INSERT INTO… SELECT into a columnstore table is performed 2. The SELECT part of the query contains a batch mode hash join 3. The query can’t immediate get […]

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