Press "Enter" to skip to content

Category: Extended Events

Tracking Database Errors with Extended Events

Published 2022-12-07 by Kevin Feasel

Eitan Blumin is watching you:

But interestingly enough – we would be getting an added benefit here. Even if there is no SQL injection attack, it’s still possible that such errors would be raised by the application – simply due to bugs.

Furthermore, these errors in the database may be happening without anyone even noticing! How could that be, you ask? Well, it could be due to bad error handling that “swallows” the error entirely, or because the errors are logged but no one is bothering to look at the logs, or maybe because the errors are caught but an undetailed error message is logged/displayed to the user (I can’t even count how many times I encountered “general database error” messages in applications), or because the developers simply decided to mark this as a “known issue” that they didn’t bother to fix and they didn’t think to ask their DBA about it… The reasons are numerous and varying.

Click through for the scripts. I had built something similar about a decade ago, a simple WPF app which watched for errors. I messaged him with something like “You missed a comma in that IN clause” and I saw him pop up from his cubicle and look around, trying to figure out how I could peek over his shoulder and see the query.

1 Comment

Where Extended Events Go by Default

Published 2022-12-01 by Kevin Feasel

Tom Zika is curious:

Have you ever wondered where the .xel file is saved when you create a new Extended Event session and don’t specify the full path (just the file name)?

Like so: [image removed because you should go to Tom’s site and see it, ed.]

Well, so did I and here’s what I’ve found out.

Click through to learn where these files end up if you don’t specify anything.

Comments closed

Extended Event Performance Metrics in SQL Server 2022

Published 2022-11-29 by Kevin Feasel

Mitchell Sternke looks at some new extended events:

Running Extended Event (XEvent) sessions on SQL Server has a cost. Since XEvents was designed for high-performance, this is usually unnoticeable. However, it can become an issue depending on which events, actions, and other XEvent features are in use. New metrics available in SQL Server 2022, in Azure SQL Database, and in Azure SQL Managed Instance can help you understand the performance impact of using XEvents in your database.

The sys.dm_xe_session_events DMV (sys.dm_xe_ database_session_events on Azure SQL Database) provides one row for each event found in an active session definition, allowing you to see all events that are currently publishing on your SQL Server instance. Four new columns have been added to help with troubleshooting performance:

Read on to learn more about these columns and what they can do for you.

Comments closed

Extended Event Duration Filtering and Looping

Published 2022-10-20 by Kevin Feasel

Erik Darling notes a problem with time-based filters on operations:

There are six waitfor commands that each pause for 1 second. In between them are queries that finish in milliseconds.

If I watch the event output, eventually, I’ll see this:

Okay, so the stored procedure took more than 5 seconds, but… no individual query took more than 5 seconds.

This happens a lot and I’m not sure there’s a good answer for it.

Comments closed

Tracking Power BI Desktop Activity in SQL Server

Published 2022-10-06 by Kevin Feasel

Chris Webb looks in on things:

Something I do all the time when performance tuning Power BI is use SQL Server Profiler to monitor query and refresh activity. There’s a handy external tool that lets you open up Profiler with a connection to Power BI Desktop; if you’re using Power BI Premium you can also connect Profiler up to a published dataset using the XMLA Endpoint. Profiler is a bit old-school though and likely to lead to snarky comments from SQL Server DBAs (it’s not deprecated for Analysis Services though!) who’ll say you should be using Extended Events (aka xEvents) instead. And guess what – did you know you can use Analysis Services xEvents to monitor activity in Power BI Desktop?

It’s the power of Extended Events.

Comments closed

Tracking Bulk Insert Usage with Extended Events

Published 2022-09-30 by Kevin Feasel

Grant Fritchey wants to see if you’re bulking up:

Wouldn’t it be great to be able to directly monitor specific behaviors within SQL Server, like, oh, I don’t know, knowing exactly when, and how, someone is using BULK INSERT? Well, you can, thanks to Extended Events through the bulk_insert_usage event.

Click through for an overview of what this event provides, as well as what it doesn’t provide.

Comments closed

query_antipattern_type Extended Event

Published 2022-09-13 by Kevin Feasel

Aaron Bertrand is intrigued:

But one thing that caught my eye in all the ruckus is a new Extended Event called query_antipattern, which is a lot more up my personal alley. You may have come across my Bad Habits series, or might have seen me rant about some of these in person. I think this is a promising compromise between manually parsing every single query and just not realizing how many little things are collectively bringing SQL Server to its knees.

This event is not yet documented, but it seems like it could be some combination of runtime code analysis and execution plan inspection. Right now, all we have to go on is a set of cryptic values in sys.dm_xe_map_values:

Read on to see those values and Aaron’s speculation.

Comments closed

Filtered XML Deadlock Reports with Extended Events

Published 2022-07-15 by Kevin Feasel

Grant Fritchey digs into a useful Extended Event:

One of my favorite little bits of information about Extended Events is the fact that everyone running a full instance of SQL Server has deadlock information available to them, even if they never enabled Trace Flag 1222 through the system_health session. That captures the xml_deadlock_report which has the full deadlock graph. However, what if you want to capture deadlock info, but, you’re dealing the GDPR, and transmitting query values could be problematic? Enter xml_deadlock_report_filtered.

Read on to see how it works, though note Grant’s warning that this is a non-documented event.

Comments closed