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More Consistent Execution Plan Timings in SQL Server 2022 The updated showplan schema shipped with SSMS 19 preview 2 c...

Empty Parallel Zones An empty parallel zone is an area of the plan bounded by exchanges (or the leaf level) containing...

Incorrect Results with Parallel Eager Spools and Batch Mode You might have noticed a warning at the top of the release ...

Closest Match with Sort Rewinds In When Do SQL Server Sorts Rewind? I described how most sorts can only rewind when th...

SQL Server 2019 Aggregate Splitting The SQL Server 2019 query optimizer has a new trick available to improve the perfor...

A bug with Halloween Protection and the OUTPUT Clause Background The OUTPUT clause can be used to return results fro...

Pulling Group By Above a Join One of the transformations available to the SQL Server query optimizer is pulling a logic...

Batch Mode Bitmap Demos This is a companion post to my main article Batch Mode Bitmaps in SQL Server . This post provid...

Apply versus Nested Loops Join SQL is a declarative language. We use SQL to write a logical query specification that d...

Parameter Sniffing, Embedding, and the RECOMPILE Options Parameter Sniffing Query parameterization promotes the reuse ...

Aggregates and Partitioning The changes in the internal representation of partitioned tables between SQL Server 2005 an...

Working Around Missed Optimizations In my last post , we saw how a query featuring a scalar aggregate could be transfor...

Optimization Phases and Missed Opportunities There are two complementary skills that are very useful in query tuning. O...

Improving Partitioned Table Join Performance The query optimizer does not always choose an optimal strategy when joinin...

Hello Operator, My Switch Is Bored This post is in two parts. The first part looks at the Switch execution plan operato...

Optimizer Limitations with Filtered Indexes One of the filtered index use cases mentioned in the product documentation ...

A creative use of IGNORE_DUP_KEY Let’s say you have a big table with a clustered primary key, and an application that i...

Dynamic Seeks and Hidden Implicit Conversions A LIKE predicate with only a trailing wildcard can usually use an index...

Avoiding Uniqueness for Performance In my last post, Enforcing Uniqueness for Performance , I showed how using a unique...

Enforcing Uniqueness for Performance A little while back, I posted a short series on seeks and scans: When is a Seek ...