Fabiano Amorim has taken the time to really drill into the behavior of a small set of execution plan operators in an effort to explain the optimizer's behavior. He's explored why things happen, how you can change them, positively or negatively, and he's done it all in an approachable style.… Read more
'Split, Sort & Collapse' is, happily, not a description of the intrepid Fabiano after his epic series of articles about the ShowPlan operators. With renewed stamina, Fabiano continues his mission to describe all the major operators by explaining the Trivial Plan and the power of unique indices.
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When Fabiano agreed to undertake the epic task of describing each showplan operator, none of us quite predicted the interesting ways that the series helps to understand how the query optimiser works. With the Merge Interval, Fabiano comes up with some insights about the way that the Query optimiser handles overlapping ranges efficiently… Read more
Did you ever wonder how and why your indexes affect the performance of joins? Once you've read Fabiano's unforgettable explanation, you'll learn to love the MERGE operator, and plan your indexes so as to allow the Query Optimiser to use it.
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Fabiano introduces another ShowPlan operator that is used to build a query plan, or perform an operation specified in the DML. Once again, Fabiano demonstrates why it is important to be aware of these operators when getting queries to perform well.… Read more
Fabiano continues his mission to explain the Query Optimiser in practical terms, describing, one week at a time, all the major Showplan Operators used by SQL Server's Query Optimiser to build the Query Plan. He discusses the Stream Aggregate function and shows how easy it is to get performance gains in GROUP BY clauses by choosing the right index.… Read more
The Row Count Spool operator is a simple component in an execution plan that can make an enormous difference to SQL query plans that would otherwise read a table on every row of the inner input to a nested loop. As this is a common type of query, it illustrates the power that a knowledge of your showplan operators can give you.… Read more
Continuing to illuminate the depths of SQL Server's Query Optimizer, Fabiano shines a light on the sixth major Showplan Operator on his list: the Lazy Spool. What does the Lazy Spool do that's so special, how does the Query Optimizer use it, and why is it so Lazy? Fabiano explains all...… Read more
For the fifth part of Fabiano's mission to describe the major Showplan Operators used by SQL Server's Query Optimiser, he introduces the spool operators and particularly the Eager Spool, explains blocking and non-blocking and then describes how the Halloween Problem is avoided.… Read more
Fabiano continues in his mission to describe the major Showplan Operators used by SQL Server's Query Optimiser. This week he meets a star, the Key Lookup, a stalwart performer, but most famous for its role in ill-performing queries where an index does not 'cover' the data required to execute the query. If you understand why, and in what circumstances, key lookups are slow, it helps greatly with optimising query performance. … Read more
The third part of Fabiano's mission to describe the major Showplan Operators used by SQL Server's Query Optimiser continues with the 'Compute Scalar' operator. Fabiano shows how a tweak to SQL to avoid a 'Compute Scalar' step can improve its performance.… Read more
Fabiano continues in his mission to describe, one week at a time, all the major Showplan Operators used by SQL Server's Query Optimiser to build the Query Plan. This week he gets the Concatenation operator .… Read more
As part of his mission to explain the Query Optimiser in practical terms, Fabiano attempts the feat of describing, one week at a time, all the major Showplan Operators used by SQL Server's Query Optimiser to build the Query Plan. He starts with Assert… Read more
