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Day: October 28, 2021

Multi-Threading with dbatools

Published 2021-10-28 by Kevin Feasel

Andy Levy has some lessons learned:

Over the summer, I spent some (a lot of) time working on updates to a script at work which runs multiple processes in parallel. Everything seemed to work OK for a while, but then everything broke. It broke right around the time dbatools 1.1 dropped, so I started thinking that something must have changed there. Turns out, it was entirely my fault and I hope this post will help you avoid the same trap.

Don’t fall into the same traps Andy did; read the whole thing.

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System-Versioned Ledger Tables

Published 2021-10-28 by Kevin Feasel

Randolph West has a series on ledger tables in SQL Server. First up is a primer on the topic:

System-versioned ledger tables leverage the same technology: there is a table with current data in it, and an underlying history table which keeps track of changes. However, it uses a cryptographic chain that provides digital forensic evidence of tampering. Yes, if you’ll pardon the use of this phrase, I’m talking about a blockchain.

This is not a cryptocurrency. No one is using expensive graphics cards to produce a fiat currency in someone’s basement. Instead, each transaction affecting the database in question is cryptographically hashed using a SHA-256 algorithm and then stored somewhere off-site.

Part two separates out the two types of ledger table:

This week we will look at the different types of ledger table: append-only and updatable.

Unlike temporal tables, a ledger table can be append-only which makes it immutable. You can only insert data and therefore it does not need a history table. In fact, you may be using append-only tables in your data warehouse already. While this is secure, it may not be practical.

Part three covers limitations:

Every choice we make is a trade-off. New features have limitations, and ledger tables are no exception.

Some of these limitations are perfectly sensible. For example, the whole point of ledger tables is to ensure that we can provide tamper evidence. This necessarily means you can’t turn it off once it’s enabled, unless you drop the database entirely — this is just one scenario where a full defence-in-depth strategy is required.

Part four is the one I’ve been waiting for—an explanation why you probably don’t need this:

After writing several posts about a neat feature in Azure SQL called system-versioned ledger tables, it reminded me about something I’ve wanted to say for a number of years now, outside of snarky tweets.

Here goes:

You don’t need a blockchain.

In the vast majority of use cases, you need a properly audited relational database system with ACID compliance and a good recovery strategy.

There are very specific use cases in which data hashes and ledger tables make sense.

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Adding an Animated GIF to Power BI Reports

Published 2021-10-28 by Kevin Feasel

Ed Hansberry works around a Power BI limitation:

It is easy to add an animated GIF to your Power BI Reports. However, if you just add it as an image, it won’t animate. You’ll just get a static image.

Animated GIFs can be useful in reports to explain new features to users, or on hidden developer pages showing how certain things were done.

Click through for instructions on how to include an animated GIF on your Power BI report. Just make sure to pronounce it the right way.

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More Efficient Pivoting

Published 2021-10-28 by Kevin Feasel

Dave Mason is on the hunt:

While working with some poorly performing code in T-SQL that used a PIVOT operator, I wondered if there was a more efficient way to get a result set of pivoted data. It may have been a fool’s errand, but I still wanted to try. It dawned on me that I could use the STRING_AGG() function to build a delimited list of pivoted column names and values. From there, I’d have to “shred” the delimited data to rows and columns. But how?

Read on to see how.

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Compressing Multiple Files into an Archive with Powershell

Published 2021-10-28 by Kevin Feasel

Patrick Gruenauer zips all the files:

Compressing files is a common task. For saving time, you can use PowerShell to automate the compression process. In this blog post I will show you how to compress multiple folders at once with the PowerShell Cmdlet Compress-Archive. The compressed zip files will be stored separately in a specific file. Let’s dive in.

Click through for a script which compresses each folder in its own zip file.

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