Category: Bugs

Brent Ozar finds a bug:

When you turn on last actual plans in SQL Server 2019 and newer:

ALTER DATABASE SCOPED CONFIGURATION SET LAST_QUERY_PLAN_STATS = ON;

The system function sys.dm_exec_query_plan_stats is supposed to show you the last actual query plan for a query. I’ve had really hit-or-miss luck with this thing, but my latest struggle with it is that two of the numbers are flat out wrong. It mixes up CPU time and elapsed time.

Here’s a simple query to prove it:

Click through for a demonstration of the bug.

Leave a Comment

Warda Bibi explains an issue:

Recently, we encountered a production incident where PostgreSQL 16.8 became unstable, preventing the application from establishing database connections. The same behavior was independently reproduced in a separate test environment, ruling out infrastructure and configuration issues. Further investigation identified the pg_prewarm extension as the source of the problem.

This blog post breaks down the failure, the underlying constraint, why it manifests only under specific configurations, and the corresponding short-term mitigation and long-term fix.

Click through for those details. The bug is no longer an issue as of PostgreSQL 16.10.

Leave a Comment

Paul Randal re-tells a story:

Jonathan had a client issue recently where SQL Server’s buffer pool had been forced down to a ridiculously small size, only a few hundred MB, but the OS also showed basically no free memory. Page Life Expectancy was zero! What was going on?

From investigating SQL Server’s memory usage, the memory manager showed that target and total memory were the same, at only 1.2GB, and lock pages in memory was correctly set.

Read on for Jonathan’s troubleshooting steps and what he discovered.

Comments closed

Rebecca Lewis lays out the consequences of an existing bug:

If you use SESSION_CONTEXT() in any query that can run with parallelism, you may be getting wrong results right now and not know it. This is not new. It has been a documented known issue since January 2022. It shipped unfixed in SQL Server 2019, 2022, and 2025 — and as of 2025 CU2 (February 12, 2026), it is still not resolved.

This is easy to miss. It’s buried in the Known Issues section of CU release notes, and the symptoms — wrong results or dump files — do not obviously point back to SESSION_CONTEXT.

Read on to learn more about the issue, the current workaround, and how you can discern whether you are experiencing the issue today.

Comments closed

Brent Ozar checks out the list:

Whenever a brand spankin’ new version of any software comes out, there are bugs, and SQL Server is no exception. This has led to a mentality where folks don’t wanna install a new version of SQL Server until the first couple of Cumulative Updates come out, hopefully fixing the first big round of bugs.

So… are there bugs this time around?

Read on to see the list. Though I will note that the SQL authentication logins being slower isn’t a bug. It’s a consequence of improving security via PBKDF2 and cranking up the number of iterations. On net, this is a good thing because it makes brute-force password attacks orders of magnitude more difficult while having negligible impact on legitimate users. In the post Brent links, Vlad Drumea has a comment talking about going from sub-1ms to 150ms per login attempt in his tests, and the neat thing about PBKDF2 is that it scales linerally with number of iterations, so as hardware gets faster and faster, you can increase the number of iterations necessary and maintain a fairly standard range of login times.

Comments closed