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Category: Parallelism

Why Does My Serial Query Have Parallel Waits?

September 23, 2019 Erik Darling Leave a comment

Harkening In dramatic fashion, I’m revisiting something from this post about stats updates. It’s a quick post, because uh… Well.…

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Posted in: Parallelism, SQL Saturday

Spills Week: Exchange Spill Excruciation

August 2, 2019 Erik Darling 1 Comment

Many Have Entered, Few Have Left For some background on Exchange Spills, check out this Great Postâ„¢ by Joe. The…

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Posted in: Execution Plans, Parallelism, Spills, SQL Server

A Trick For Dealing With Table Variable Modification Performance

July 17, 2019 Erik Darling 2 Comments

Don’t Want None One of the many current downsides of @table variables is that modifying them inhibits parallelism, which is…

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Posted in: Parallelism, Query Tuning

The Difference Between Statistics Time And Plan Operator Times

July 9, 2019 Erik Darling 3 Comments

Goal Posts When you’re measuring query changes to see if your performance changes have made a difference, a common way…

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Posted in: Execution Plans, Parallelism, Query Tuning, SQL Server

Too Much Of A Harmless Wait Can Be Harmful

July 5, 2019 Erik Darling Leave a comment

Absence Of Evidence There’s a pinky-out saying about wine: don’t hate the grape. People say it because the same kind…

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Posted in: Parallelism, SQL Server, Wait Stats

A Trick For Working Around Scalar UDF Performance Issues

July 2, 2019 Erik Darling 2 Comments

Mr. Duster

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Posted in: Execution Plans, Parallelism, Query Tuning, SQL Server

CMEMTHREAD Waits Generated By Query Store

June 28, 2019 Erik Darling 4 Comments

Memethread    

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Posted in: Execution Plans, Parallelism, Query Tuning, SQL Server

Bad Guesses and Bad Choices: Does Tricky Batch Mode Help?

May 22, 2019 Erik Darling 1 Comment

Notes and Notability In the last post, I showed you a query where a bad plan was chosen because of…

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Posted in: Batch Mode, Execution Plans, Parallelism, SQL Server

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