Why the Optimizer Doesn't Use Buffer Pool Knowledge Paul Randal describes why the optimizer doesn’t use buffer pool contents for plan generation and details the potential dangers if it did. Paul Randal ◆ November 30, 2021 3
The Adaptive Join Threshold Paul White discusses how an adaptive join decides to use a batch mode hash join or row mode apply and includes details of the threshold calculation. Paul White ◆ November 4, 2021 0
Finding Distinct Values Quickly Paul White explains a few different ways to retrieve distinct values from a table, including some big "it just runs faster" wins in SQL Server 2019. Paul White ◆ March 17, 2020 1
The Eager Index Spool and The Optimizer Paul White looks at the Eager Index Spool execution plan operator, and the optimizer rules capable of adding it into plans. Paul White ◆ November 22, 2019 0
Nested Loops Joins and Performance Spools Paul White on performance spools, and how they can be used by the optimizer to reduce the estimated cost of nested loops joins. Paul White ◆ September 25, 2019 2
Batch Mode Normalization and Performance Paul White takes a deep-dive look at the internals of batch mode data normalization and how it can affect execution plans and performance. Paul White ◆ September 5, 2019 1
Batch Mode Bitmaps in SQL Server Paul White takes a deep dive into SQL Server batch mode bitmaps revealing undocumented details that can greatly impact performance. Paul White ◆ August 23, 2019 3
Some ANY Aggregate Transformations are Broken Paul White explores two cases where the introduction of the internal ANY aggregate by the optimizer may cause wrong results. Paul White ◆ July 1, 2019 8
SQL Server Join Estimation using Histogram Coarse Alignment Paul White dives into histograms and explains how the optimizer uses coarse alignment for cardinality estimates. Paul White ◆ November 20, 2018 1
Optimization Thresholds – Grouping and Aggregating Data, Part 5 In the conclusion of his series on grouping and aggregation costs, Itzik Ben-Gan reveals some of the math behind seek vs. scan decisions. Itzik Ben-Gan ◆ August 8, 2018 2
Optimization Thresholds – Grouping and Aggregating Data, Part 4 In the fourth installment of his series on optimization thresholds, Itzik Ben-Gan looks at how SQL Server applies costs to parallel operations. Itzik Ben-Gan ◆ July 11, 2018 7
