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Author: Kevin Feasel

SELECT FOR UPDATE in PostgreSQL

Published 2025-04-09 by Kevin Feasel

Umair Shahid preps for an update:

When multiple transactions need to modify the same rows, ensuring data consistency can become tricky. A single wrong approach to locking can lead to suboptimal performance or even bring your application to a standstill as numerous transactions block one another. One tool in PostgreSQL’s arsenal to handle concurrency is SELECT FOR UPDATE. It allows you to lock specific rows before updating them, preventing other transactions from modifying those rows until your transaction completes.

In this blog, we will dive deep into SELECT FOR UPDATE in PostgreSQL. We will explore how it helps in reducing contention, avoiding deadlocks, and ultimately boosting performance when dealing with highly concurrent applications.

Click through to understand how this works and also some notes on when to use it and when not to use it.

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Common Data Model Connector for Synapse Spark 3.4

Published 2025-04-08 by Kevin Feasel

Richard Swinbank deals with a totally-not-deprecated platform:

The underlying problem here appears to be that the Spark connector is simply not supported in v3.4. There’s very little I can find to officially confirm or deny this, but an answer to this question on Microsoft Q&A backs this up. The answer also suggests a few options, including:

  1. downgrade to Spark 3.3 – this isn’t an option because it’s end-of-life
  2. migrate to Fabric – long term this is good idea, but it’s not a quick fix for this problem.
  3. use alternative data access methods, e.g. using the Azure Data Lake Storage Gen2 connector.

In this article, I take a look at option (3).

Click through for Richard’s workaround.

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CI/CD Announcements during FabCon

Published 2025-04-08 by Kevin Feasel

Kevin Chant keeps us up to date:

Microsoft Fabric Variable libraries were announced during the keynote at the Microsoft Fabric community conference. Which caused some excitement.

Variable libraries are an upcoming preview item that will enable developers to manage configurations within a workspace. Reducing the need for custom development work after deployments.

You will be able to achieve this by creating a Variable library in each workspace. From there, configure the individual variables for that workspace. Improving your CI/CD experience.

Click through to see more about that, as well as several other interesting announcements.

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Handling NULL in T-SQL

Published 2025-04-08 by Kevin Feasel

Chad Callihan deals with non-existent data:

Handling NULL values can be a challenge and may lead to unexpected query results when mixed in with non-NULL values. Thankfully, there are a few SQL Server functions devoted to handling NULL values. Let’s look at two of them. The first, NULLIF, will help you to return a NULL value. The second, ISNULL, will help you with an alternative to a NULL value if you need another value in its place.

For the longest time, I strongly preferred COALESCE() over ISNULL() because of how it can handle multiple scenarios, as well as it being ANSI SQL syntax. But it turns out that, if you do only have two things to compare, ISNULL() is a little bit faster.

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Fuzzy Matching in Power Query and Power BI

Published 2025-04-08 by Kevin Feasel

Reza Rad does a bit of a match:

Have you ever wanted to match two tables together but not on exact matches, but also on a threshold of similarity? if your answer to this question is yes, then this feature is built for you. Let’s explore in details how the fuzzy matching works in Power BI. To learn more about Power BI, read Power BI from Rookie to Rock Star.

As always, Reza has a video and a blog post for us, explaining how the fuzzy matching process works and some of the knobs you can control. In the comments, Reza even digs up the specific algorithm that Microsoft uses for fuzzy matching.

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Setting TEXTSIZE in SQL server

Published 2025-04-08 by Kevin Feasel

Steve Jones limits results:

There is a SET command in SQL Server that changes how much data is returned from some fields. This short post shows what I learned about the SET TEXTSIZE command.

I’m pretty sure that, if I’ve ever used this command before, it was by accident. It’s kind of a neat concept in how it can limit the result size of larger blocks of text, but I think it’s too limiting to be a good solution save for some very specific circumstances.

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Filtering Weekdays using DAX

Published 2025-04-08 by Kevin Feasel

Marco Russo and Alberto Ferrari show that tracking weekdays is like an onion:

Computing time intelligence calculations in DAX is rather simple. However, as soon as the requirements are not trivial, the complexity of formulas skyrockets, and it is necessary to have a very good understanding of several details about DAX to obtain a good formula. In this article, we show a simple requirement: the need to maintain a filter on weekdays while computing time intelligence. As you are about to read, it will require several complex steps despite being a simple requirement; but let us start by clarifying what we want to obtain and what a filter-preserving column is.

Click through for the full article.

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Avoid aggregate in R on Wide Matrices

Published 2025-04-07 by Kevin Feasel

Ali Oghabian shares some hard-earned advice:

The aggregate function can be very useful in R, allowing one to run a function (e.g. mean) within groups of rows, in each column in a matrix/data-frame and organize the results in an easy-to-read table. However, the function takes long to run for very wide matrices and data frames, where the number of the columns are large. I this post I demonstrate the issue and show a couple of nice solutions that at least for the example cuts down the time to 15% and even less, compared to the run-time of the aggregate function.

Click through for a demo. Granted, this is a matrix with 10,000 columns, so I’m not sure how this applies to narrower matrices. H/T R-Bloggers.

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Locking Down a PostgreSQL Database

Published 2025-04-07 by Kevin Feasel

Thom Brown shares some advice:

As you may have heard, there are reportedly over 1,500 PostgreSQL servers that have been exploited to mine Bitcoin. And your server could be next if you haven’t taken precautions. Firstly, you need to update to the latest minor release, just so no known exploitable bugs exist on your system. But regardless of whether you update, your PostgreSQL instance could still be misconfigured in a way that would allow unwelcome visitors access, so you need to make sure you shore up your defenses. Here are some steps you should take.

Click through for some solid guidance.

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