22-25 April 2026

The Ascending Key Problem

2025

TL; DR

You're constantly loading new sales data in, but when users run reports for recent sales like today or yesterday, you get bad query plans. Fix it with trace flags 2389 and 4139.

Session Details

You're constantly loading new sales data in, but when users run reports for recent sales like today or yesterday, you get bad query plans.

Brent Ozar will explain how statistics are involved, why you can't update them frequently enough to get it right, and how trace flags 2389 and 4139 help performance.

This session is for database administrators who are comfortable reading query plans and interpreting the output of DBCC SHOW_STATISTICS.

3 things you'll get out of this session

* Learn what the Ascending Key Problem is * See improvements in recent compatibility levels * Identify when those still aren't enough, and you need to use trace flags 2389 and 4139

Speakers

Brent Ozar

brentozar.com

Brent Ozar's previous sessions

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