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Parallel Index Building Execution Plan SQL Server doesn't support parallel modifications to a b-tree index. That might sound surprising....

Erik Darling ( @erikdarlingdata ) shared an interesting SQL Server execution plan with me recently. The demo script is at the end of this ar...

Setting a Fixed Size for Transaction Log VLFs The documentation has this to say about virtual log file (VLF) sizes: ...

Why Batch Mode Sort Spills Are So Slow Batch mode sorting was added to SQL Server in the 2016 release under compatib...

Fast Key Optimization for Row Mode Sorts SQL Server row-mode sorts generally use a custom implementation of the well-kn...

Reducing Contention on the NESTING_TRANSACTION_FULL latch Each additional worker thread in a parallel execution plan ex...

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

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

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

Incorrect Results Caused By Adding an Index Say you have the following two tables, one partitioned and one not: CREATE...

Two Partitioning Peculiarities Table partitioning in SQL Server is essentially a way of making multiple physical tables...

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

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

Execution Plan Analysis: The Mystery Work Table I love SQL Server execution plans. It is often easy to spot the cause o...

Optimizing T-SQL queries that change data Most tuning efforts for data-changing operations concentrate on the SELECT s...

MERGE Bug with Filtered Indexes A MERGE statement can fail, and incorrectly report a unique key violation when: The ...

Query Optimizer Deep Dive - Part 4 This is the final part in a series of posts based on the content of the Query Optim...

Query Optimizer Deep Dive – Part 3 This is the third in a series of posts based on the content of the Query Optimizer ...

Query Optimizer Deep Dive – Part 2 This is the second in a series of posts based on the content of the Query Optimizer...

Query Optimizer Deep Dive - Part 1 This is the first in a series of posts based on the content of the Query Optimizer ...