Connect Digest : 2011-05-23

Next week I'll be up in Alaska for SQL Cruise, so I'll be skipping at least one digest. This week I gathered a few engine-related issues, two involving what the engine does while an index is being created. The most important one, though, at least IMHO, is the first one listed, involving a hashing algorithm fix that is in SQL Server 2008 R2 – but with no plans to fix it for SQL Server 2008. I wonder if someone should file a separate, 2008-specific bug?

#458091 : Change Lock Resource Hashing Algorithm to Reduce Likelihood of Collisions

#581056 : Indexed view creation causes queries on the base table to block

#478568 : SSMS Gets Blocked and Locks Up During Index Creation

#125549 : Poor execution plan with CTE

And finally, this issue ("high degrees of parallelism cause incorrect results to be observed more frequently" according to KB #981502) is one that has been fixed in SP1 for SQL Server 2008 R2, but it requires a trace flag (in Denali, it will be on by default, so you won't need a trace flag). I'm not telling you about this so you'll go and vote for this issue, but rather just to make you aware of it. The KB article states that the fix is in various CUs for 2005, 2008 and 2008 R2, but as the Connect item implies, the fix may not actually work in all cases, and requires the trace flag for others.

#642790 : Parallel query plan returns different results every time that you run the query


Aaron Bertrand

I am a passionate technologist with industry experience dating back to Classic ASP and SQL Server 6.5. I am a long-time Microsoft MVP, write at Simple Talk, SQLPerformance, and MSSQLTips, and have had the honor of speaking at more conferences than I can remember. In non-tech life, I am a father of two, a huge hockey and football fan, and my pronouns are he/him. If I've helped you out, consider thanking me with a coffee. :-)