SQL Optimizer Archives - SQLPerformance.com

Cardinality Estimation: Combining Density Statistics

Paul White (@SQL_Kiwi) whips out the debugger while showing how SQL Server derives estimates when combining multiple, single-column statistics.

Paul White ◆ August 2, 2017

4

Properly Persisted Computed Columns

Paul White (@SQL_Kiwi) walks through a new trace flag in SQL Server 2016 designed to yield better execution plans (and performance) for queries involving computed columns.

Paul White ◆ May 25, 2017

2

UNION ALL Optimization

Paul White (@SQL_Kiwi) digs into row goals as he explains some interesting and inconsistent behavior with UNION ALL queries in SQL Server.

Paul White ◆ May 10, 2017

0

Cardinality Estimation for a Predicate on a COUNT Expression

Paul White (@SQL_Kiwi) takes you on an optimizer journey, exploring how SQL Server comes up with cardinality estimates for COUNT queries.

Paul White ◆ April 12, 2017

5

Plan Explorer 3.0 Webinar – Samples and Q & A

Aaron Bertrand (@AaronBertrand) follows up a recent webinar on Plan Explorer 3.0 with answers to about two dozen audience questions.

Aaron Bertrand ◆ September 15, 2016

0

SQL Server 2016 Temporal Table Query Plan Behaviour

For this month's T-SQL Tuesday, Rob Farley takes a look at a couple of unexpected aspects of query plans you might observe when using Temporal Tables in SQL Server 2016.

Rob Farley ◆ June 14, 2016

0

What's "Actually" going on with that Seek?

Rob Farley (@rob_farley) digs deeper into seeks and actual rows read, demonstrating a case where you want a non-sargable expression in the WHERE clause.

Rob Farley ◆ June 10, 2016

12

Performance Surprises and Assumptions : DATEADD

Aaron Bertrand (@AaronBertrand) explores yet another scenario where a date/time function seems to cause the optimizer to behave unexpectedly.

Aaron Bertrand ◆ April 11, 2016

12

Changes to a Writable Partition May Fail Unexpectedly

Paul White (@SQL_Kiwi) shows how an update may fail when a partition has some data on a read-only filegroup, and explains several workarounds.

Paul White ◆ March 22, 2016

0

Can ColumnStore Help Pagination Workloads?

Aaron Bertrand (@AaronBertrand) revisits an older post about SQL Server pagination to see if any implementation of ColumnStore indexes can improve performance.