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Curated SQL Posts

Removing a Node from Elasticsearch

Published 2023-04-26 by Kevin Feasel

The Big Data in Real World team spams the delete button:

Shutting down a node abruptly is not the right way to decommission or remove a node from the Elasticsearch cluster. Doing so will cause your shards which are replicated to go down in replication and it could cause disruption to the clients who are currently consuming data from Elasticsearch.

Proper way to decommission or remove a node from Elasticsearch is to add the host to the exclusion list.

Click through to learn how to do this.

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Updating Power BI Dataset Compatibility Level

Published 2023-04-26 by Kevin Feasel

Kurt Buhler wants the newest toys:

In the monthly updates for Power BI, there may be new features that appear for preview. For example, in the April 2023 update, dynamic format strings for measures released into preview. This feature allows you to specify a DAX format string expression for measures, like you already could do with calculation groups.

In Power BI, these features become readily available once enabled from the ‘Preview features’ section of the ‘Options’ menu. However, when you are connected to a dataset or metadata with Tabular Editor, the properties will not be visible. That’s because behind-the-scenes, Power BI upgrades the model compatibility level when using a preview feature for the first time.

Click through to learn how.

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ScriptDOM Now Open Source

Published 2023-04-26 by Kevin Feasel

Drew Skwiers-Koballa has great news for us:

ScriptDOM is a powerful .NET library for code parsing, generating an abstract syntax tree (AST) that can be leveraged to apply code formatting, detect antipatterns, and more. We are thrilled to announce that the source code for ScriptDOM has been released into open source under the MIT license and is available on GitHub.  In addition, ScriptDOM is now distributed by Microsoft as a standalone NuGet package.

This is big and good news. We’ve been able to use ScriptDOM for quite a while, but now that we can extend and improve the library, that’s great.

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Understanding Log Send Queue, Redo Queue, and Redo Rate

Published 2023-04-26 by Kevin Feasel

Greg Dodd explains three terms:

A quick description of 3 metrics that SQL tracks in Availability Groups. These metrics are important when evaluating the health of your Availability Group, and knowing what sort of data loss you might face in a failover. Remember, just because you told SQL to make your AAG Synchronous, doesn’t mean you won’t have data loss.

Click through for the definitions.

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Loading WhoIsActive Data on Azure SQL DB

Published 2023-04-26 by Kevin Feasel

Andrea Allred wants to know who’s doing what on this system:

I needed to collect sp_WhoIsActive into a table, but the twist was that it is on my Azure Managed Database, so I had to get creative with how I did it. We needed an Azure Pipeline to run it, but we wanted to record it every minute and firing a pipeline every minute adds up fast. So we decided that we would kick it off once an hour and have the process wait for a minute and then fire until the hour ended. Then it fire again at the top of the next hour and the same process would happen.

That’s an interesting way to do it. Another alternative might have been an Azure function app, which you could schedule to run every minute. I think that’d be a lot less expensive than running an Azure Pipeline, and this goes to show you that there are many ways to solve the same problem in Azure.

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9 Gotchas Working with Postgres

Published 2023-04-26 by Kevin Feasel

Phil Booth categorizes various mistakes as learning experiences:

Previously on Extreme Learning, I discussed all the ways I’ve broken production using healthchecks. In this post I’ll do the same for PostgreSQL.

The common thread linking most of these gotchas is scalability. They’re things that won’t affect you while your database is small. But if one day you want your database not to be small, it pays to think about them in advance. Otherwise they’ll came back and bite you later, potentially when it’s least convenient. Plus in many cases it’s less work to do the right thing from the start, than it is to change a working system to do the right thing later on.

Click through for the nine lessons learned, eight of which are still relevant as of PostgreSQL version 12. Many of these also have analogues in the SQL Server world, e.g., don’t overuse triggers, use non-recursive methods for path traversal when possible, do add indexes on foreign keys.

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Passing the Buck: Hyperparameters Edition

Published 2023-04-25 by Kevin Feasel

John Mount is not a fan of hyperparamters:

In my opinion one can see this scam of hiding some debt in with an asset spreading.

Earliest modeling systems, such as linear regression, had no hyper-parameters. An under specified algorithm was not considered a fully specified method.

Click through for John’s thoughts on the matter. I’m sympathetic to this argument and want to bring in an extra point John didn’t make. With hyperparameter tuning, you also introduce the risk of spurious correlation between the label and input features. This is particularly relevant if changing the seed or making hyperparameter tweaks results in a major change in model effectiveness.

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Removing Chartjunk

Published 2023-04-25 by Kevin Feasel

Elizabeth Ricks takes out the trash:

Why is clutter so hard for us to let go of? Perhaps because we think something has always been there, so it must belong there and we’re afraid of what might happen if we eliminate it. Or perhaps we don’t have a good framework for evaluating whether something is useful or not. 

This same concept applies to our graphs and business communications. We tend to blindly accept the default settings of our tools and very rarely consider if the included elements actually have a purpose. The “Windows XP” question, in this case, is: does this element add enough informative value to make up for its presence?” 

This is one of the most important ideas Edward Tufte championed—other than “pie charts are dumb, so don’t use them”. I don’t completely agree with Tufte’s definition of the term, which is (paraphrasing and going by memory) any marking on the page not absolutely necessary to convey the most relevant details to a viewer. But in this post, Elizabeth shows quite a bit we could remove while losing no critical information.

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Parsing Library of Congress Data with Powershell

Published 2023-04-25 by Kevin Feasel

Robert Cain continues a series on books:

For this demo, we’ll be using an LCCN of 54-9698, Elements of radio servicing by William Marcus. When we call the web API URL in our web browser, we get the following data.

Click through for the results of the API call, which happen to be a blob of XML data. Robert shows how to get that data programmatically, then how to shred it into what he needs.

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