Compute Scalars, Expressions and Execution Plan Performance

Posted by Paul White on SQL Blog See other posts from SQL Blog or by Paul White
Published on Tue, 04 Sep 2012 22:22:00 GMT Indexed on 2012/09/05 3:45 UTC
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Filed under:

Compute Scalar

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expressions

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internals

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Performance

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query plans

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tsql

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undocumented

The humble Compute Scalar is one of the least well-understood of the execution plan operators, and usually the last place people look for query performance problems. It often appears in execution plans with a very low (or even zero) cost, which goes some way to explaining why people ignore it. Some readers will already know that a Compute Scalar can contain a call to a user-defined function, and that any T-SQL function with a BEGIN…END block in its definition can have truly disastrous consequences...(read more)

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