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Day: March 11, 2020

Developing Shiny Apps in Databricks

Published 2020-03-11 by Kevin Feasel

Yifan Cao, Hossein Falaki, and Cyirelle Simeone announce something cool:

We are excited to announce that you can now develop and test Shiny applications in Databricks! Inside the RStudio Server hosted on Databricks clusters, you can now import the Shiny package and interactively develop Shiny applications. Once completed, you can publish the Shiny application to an external hosting service, while continuing to leverage Databricks to access data securely and at scale.

That’s really cool. Databricks dashboards are nice for simple stuff, but when you really need visualization power, having Shiny available is great.

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R 3.6.3 Now Available

Published 2020-03-11 by Kevin Feasel

David Smith takes a look at R 3.6.3:

On February 29, R 3.6.3 was released and is now available for Windows, Linux and Mac systems. This update, codenamed “Holding the Windsock“, fixes a few minor bugs, and as a minor update maintains compatibility with scripts and packages written for prior versions of R 3.6. 

February 29 is an auspicious date, because that was the day that R 1.0.0 was released to the world: February 29, 2000. In the video below from the CelebRation2020 conference marking the 20th anniversary of R, core member Peter Dalgaard reflects on the origins of R, and releases R 3.6.3 live on stage (at the 33-minute mark).

I’m holding out for R 4, though then I’ll have to wait to see when SQL Server will officially support it.

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Adoption Patterns with Query Store

Published 2020-03-11 by Kevin Feasel

Erin Stellato has some thoughts on Query Store adoption:

Last fall we had a previous customer reach out for help after they had to wait 45 minutes for a database to come online after a server reboot. The database queries were blocked by QDS_LOADDB waits. There were three things in play here – the first was that they had CAPTURE_MODE set to ALL, and it should be AUTO. Second, they didn’t have trace flag 7752 enabled (the behavior of which is now the default in SQL Server 2019). And the third was that their Query Store was 100GB in size. The workload was fairly ad hoc, so these three things together caused the problem initially described. They implemented the TF, made multiple changes to the settings (set CAPTURE_MODE to AUTO, changed MAX_STORAGE_SIZE_MB to 10GB, decreased CLEANUP_POLICY to 3 days), and then Query Store was usable for them.

Read on for more examples.

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Using Query Store to Replay Workloads

Published 2020-03-11 by Kevin Feasel

John Sterrett shows us an unorthodox use of Query Store:

Today, I wanted to talk about my least favorite part of replaying workloads. It’s having an extended event or server-side trace running during a workload replay only so we can compare the results at a query-level when the replay is finished. Now, this might seem like a trivial thing but when you have workloads over 10k batch requests/sec this can consume terabytes of data quickly. The worst part is waiting to read all the data, slice and dice the data for analysis.

Starting with SQL Server 2016 there is a better and faster way to go! You can replace your extended event or server-side trace with Query Store captured data. Today, I will show you how to use the Query Store for the same purpose.

Click through for the solution.

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Finding Query Store’s Server Impact

Published 2020-03-11 by Kevin Feasel

Tracy Boggiano shows us how to track the performance impact of Query Store on an environment:

This month’s T-SQL Tuesday blogging party is brought to you well by me and I wanted to talk more about Query Store.  I did write a book on it but there if still more to know about that is not in the book.  I am sure the rest of everyone’s posts will prove enlightening and provide valuable content for folks using or looking to implement Query Store.  Someone should have told Grant to hold off a week on his post about DROP / CREATE of procedures and what happens with plan forcing so it could officially be part of the party.

I frequently get asked while presenting about the impact of running Query Store on the instance and one thing that was not in the book was the performance counters that were added to help track just that.

You should probably buy a bunch of copies of Tracy’s book. Just in case.

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Query Store and Spinlocks

Published 2020-03-11 by Kevin Feasel

David Fowler takes a look at an issue with Query Store:

We moseyed on down to the server in question to take a look at it.  One thing stood out immediately, CPU was pegged out at 100% but SQL itself didn’t actually seem to be doing anything, transactionssecond was on the floor. Unfortunately this happened a while back and I didn’t think to capture any graphs or metrics at the time so you’re just going to have to take my word for this.

After looking into a few different things, the mention of spinlock contention came up.  I’ll be honest here, actual spinlock contention is rare and is something that I’ve seen cause an issue only a handful of times so it’s something that I don’t generally get to until I’ve ruled out just about everything else.

David’s scenario was on an older patch of SQL Server and it was fixed later. It’s a good reminder to keep those servers patched.

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