Secrets of the Query Optimizer Revealed Using Trace Flag 86xx

Kevin Kline
60 minutes
Application & Database Development
You already know a thing or two about tuning a SQL query on Microsoft SQL Server. You can read an execution plan and know the most significant red flags to look for. And you have also learned how to track the most important metrics revealed by features like the SET STATISTICS. But you want to take it up another level! First, we will examine using undocumented trace flags to look at the steps of parsing, binding, and query optimization. Second, we will show how SQL Server builds internal memo structures and it interrogates the heuristics of the optimizer search space. Finally, we will discuss a secret trace flag that gives the optimizer more time to produce alternative execution plans for queries that push the boundaries of extreme database processing.

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