One of our SQL Server workloads runs many concurrent parallel queries on a possibly already busy server. Other work occurring on the server can have dramatic effects on parallel query runtimes. One way to improve scalability of parallel query runtimes …
Category: Parallelism
Detecting Query Weirdness In Query Store
Let’s Have Fun
I got asked recently if there’s a way to find parallel queries that are potentially skewed.
One thing that you’ll see quite often is that duration and cpu time aren’t much different. For parallel queries, it should …
My Favorite Cursors
Cursory
…
An Unfortunate Side Effect Of OUTPUT
Put Out
I see people using OUTPUT to audit modifications from time to time, often because “triggers are bad” or “triggers are slow”.
Well, sometimes, sure. But using OUTPUT can be a downer, too.
Let’s look at how.
A Process
…Quickly Detecting CPU and Memory Pressure On A SQL Server
Options Ahoy
There are lots of great options out there for figuring out what’s happening on a server. If you’re the kind of person still running sp_who, or sp_who2, or sp_who8045, it’s time to stop.
You’ve got much better options, …
Parallelism And Table Variables
Well, huh
…
Why Does My Serial Query Have Parallel Waits?
Harkening
In dramatic fashion, I’m revisiting something from this post about stats updates.
It’s a quick post, because uh… Well. Pick a reason.
Get In Gear
Follow along as I repeat all the steps in the linked post to:
- Load
Spills Week: Exchange Spill Excruciation
Many Have Entered, Few Have Left
For some background on Exchange Spills, check out this Great Post™ by Joe.
The root of this demo was trying to show people silly things about CTEs, how TOP can fence things off…
A Trick For Dealing With Table Variable Modification Performance
Don’t Want None
One of the many current downsides of @table variables is that modifying them inhibits parallelism, which is a problem #temp tables don’t have.
While updating and deleting from @table variables is fairly rare (I’ve seen it, but …
The Difference Between Statistics Time And Plan Operator Times
Goal Posts
When you’re measuring query changes to see if your performance changes have made a difference, a common way to do that is to use STATISTICS TIME and IO.
They’re not perfect, but the barrier to entry is super …