Regressions
[caption id="" align="alignleft" width="244" caption="Hannah Dustin, Upset about Regression"][/caption] One of the most important take-aways from David Dewitt's presentation at the PASS Summit was the level of fear within the Query Processing team at Microsoft caused by regressions. If you missed Dr. Dewitt's presentation, I tried to capture as much of it as I could here, and it will be available within the DVDs from PASS. Regression is when something moves backwards to a less perfect state. When talking about the optimizer in SQL Server, a regression is when you see a query that used to run fast in SQL Server 2000 or 2005 and suddenly after upgrading to 2005 or 2008, the exact same query now generates a different execution plan and runs slowly. Now do you know why…