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Author: Kevin Feasel

Visualizing High-Dimensional Vectors

Published 2026-04-21 by Kevin Feasel

Andrew Pruski takes a look:

Following on from my previous post on building The Burrito Bot, I want to delve into visualisation of vector embeddings that were generated from the restaurant data pulled from Google Maps.

Those embeddings had 1536 dimensions, each dimension corresponding to an axis within a high dimensional space, with embeddings that have similar meanings grouped together in that high dimensional space.

1536 dimensions…is a lot of dimensions! And for me, a hard concept to get my head around. It all just feels so abstract (to me anyway), I want to see what they actually look like!

Click through for a link to a website that helps with that visualization. It ultimately performs principal component analysis (PCA) to get 1536 (or however many) dimensions down to 3 principal components. It’s not perfect, but it does give us the ability to reason over the data.

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Simplifying a Gantt Chart

Published 2026-04-21 by Kevin Feasel

Amy Esselman looks at a chart:

Gantt charts are a popular choice for illustrating the start and duration of events, which is common practice in project management. While useful for representing timelines, these charts can quickly become busy and difficult to interpret, especially when dealing with complex workflows.

 Let’s consider an example.

Click through for that example and how you can turn a rather complex-looking chart into something a bit easier to understand and work with.

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What’s in a SQL Server File Header

Published 2026-04-21 by Kevin Feasel

Anthony Nocentino goes poking around:

I’ve been doing a deep dive into SQL Server on-disk structures lately, and one of my favorite rabbit holes is revisiting Paul Randal’s series on file header pages. If you haven’t read it, go do that now. It covers what file header pages are, what they contain, and what happens when they corrupt. This post takes that concept and runs with it. I’ll use DBCC FILEHEADER to read the file header of every user database file on a server and answer a question that comes up more than you’d think: can you determine which files belong together as a database purely from the file header, without querying sys.databases?

Read on for that answer, as well as what you cannot do with DBCC FILEHEADER.

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Query Hints and Plan Guides in RDBMS Products

Published 2026-04-21 by Kevin Feasel

Cristophe Pettus has a series in progress. The first post covers the basics of query hints and plan guides:

pg_plan_advice is expected to land in PostgreSQL 19. That makes this a good moment to look at query hints — what they are, what every other major database does with them, and how PostgreSQL ended up being the obvious outlier. Three parts. This is the first.

The second post explains why PostgreSQL hasn’t had query hints:

For most of PostgreSQL’s history, the official community position on query hints has been a polite version of “no, and stop asking.”

The position isn’t subtle. The PostgreSQL wiki maintains a page titled Not Worth Doing, and “Oracle-style optimizer hints” is listed there, right above in-process embedded mode and obfuscated function source. The companion wiki page, OptimizerHintsDiscussion, states the position outright:

Click through for a bit of history and comparison. The upcoming post promises to go into pg_plan_advice‘s proposal in more detail.

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Parameter Types in DAX User-Defined Functions

Published 2026-04-21 by Kevin Feasel

Marco Russo and Alberto Ferrari talk about type systems:

In a previous article, Introducing user-defined functions in DAX, we described the syntax for creating user-defined functions, including the two passing modes (VAL and EXPR) and the fundamental parameter types SCALAR and TABLE. In this article, we build on that foundation and focus on the complete type system, with particular attention to the reference types introduced in March 2026 that provide better documentation, stronger validation, and improved IntelliSense support.

Before diving into the new types, let us briefly recap the full picture of parameter types and passing modes available in DAX user-defined functions.

Click through for a classic deep dive from Marco and Alberto.

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Clustering in Fabric Warehouse

Published 2026-04-21 by Kevin Feasel

Koen Verbeeck speeds things up:

We are building a large warehouse in Microsoft Fabric using the warehouse. Our biggest fact tables have some performance issues when we are running our analytical queries, and it seems we cannot use indexes in the Fabric Warehouse. Is there some way to improve performance?

Click through to see how you can use clustering to improve the performance of warehousing queries, as well as some of the pre-requisites to make it work.

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Window Functions for Developers

Published 2026-04-21 by Kevin Feasel

Jamal Hansen provides an overview of window functions:

So let’s dive in. What problem do window functions solve? They seem to do aggregation-type activities, can’t GROUP BY do this?

The short answer is, not very well.

Window functions allow you to do things like calculate running totals, rankings, and moving averages, which tend to be very difficult to do otherwise because it requires a ‘window’ into a subset of the data.

Click through for the explanation, a primer on some of the types of window functions that are available, and several examples. I noticed that the code is impossible to read in light mode on the website, so either highlight it or go into dark mode, I guess.

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Enforcing Constraints across Postgres Partitions

Published 2026-04-21 by Kevin Feasel

Shaun Thomas explains a rule:

Postgres table partitioning is one of those features that feels like a superpower right up until it isn’t. Just define a partition key, carve up data into manageable chunks, and everything hums along beautifully. And what’s not to love? Partition pruning in query plans, smaller tables, faster maintenance, easy archiving of old data; it’s a smorgasbord of convenience.

Then you try to enforce a unique constraint without including the partition key, and Postgres behaves as if you just asked it to divide by zero. Well… about that.

Click through for an explanation, some workarounds that might work in specific circumstances, and a few closing remarks.

As for SQL Server, the same rule applies. If you want a unique index (which is what a unique key constraint uses under the covers), you must include the partitioning column. If you don’t include it, SQL Server will include it for you rather than giving a hard error.

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New SQL Server CVEs

Published 2026-04-20 by Kevin Feasel

Rebecca Lewis takes a look at a few more vulnerabilities Microsoft has patched in SQL Server:

This week’s Patch Tuesday landed three new SQL Server CVEs. Two are elevation-of-privilege bugs — familiar territory, we had three of those last month. The third one is different. CVE-2026-33120 is a remote code execution flaw in SQL Server 2022. CVSS 8.8. An authenticated, low-privileged login on the network can execute arbitrary code on your SQL Server.

Go. Patch. Now.

Click through for more information and be sure to get these patched.

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