Infinite Relations
Let's write a super simply query engine using the iterator model. Something like this is conceptually what the compilation target for something like SQL...
Query Operator Structures
The way we usually like to think about operators in query plans is that they're just representative of "result sets." In the Volcano model, they're just...
Should We Have Been using LLMs for Our Test Queries This Whole Time?
Longtime readers of NULL BITMAP will know that I am bullish on metamorphic and in general, property-based testing for things that are SQL-shaped. I generally...
Some Stuff I've Been Reading
I’ve been on vacation and I don’t really have an exciting post to share, but I have been reading some, so here’s a bit of my reading list, and maybe you will...
Discrete Distributions
For a while now, my favourite piece of technical writing has been Darts, Dice, and Coins: Sampling from a Discrete Distribution by Keith Schwarz. In it, he...
NULL BITMAP Two-Year ZINE Special
It has been (about) two years of writing NULL BITMAP! Thank you for reading. This issue is very special because it contains none of my technical writing, but...
Diagrams For Yourself
I have a large need of diagrams. In particular when I'm writing something longer about a query planning topic I often would like some kind of standardized...
Giving Benchmarks a Boat
I've been thinking lately about this piece from Frank Lantz about the Thielian "the Olympics, but you take performance-enhancing drugs." The pitch being...
Bloom Filter Sizing
Here's a question: say I have two streams of objects I want to construct Bloom filters over, one stream is red and one stream is blue and they're about the...
NULLBITMAPGPT
I don't know if you've all been paying attention, but this is the ONE HUNDREDTH NULL BITMAP?? To celebrate, I've heard people are really into "next token...
Unified Memory Management
There's a trend in database memory management design that I'm really excited about, and that is rethinking the abstraction boundaries of the buffer pool. I'm...
Caching is an Abstraction, not an Optimization
I've always been told that caching is a tool to make software faster. That, given some careful considerations to consistency, caching makes it so that when...
Monotone Functions and Cache Lines
If you've taken a calculus class your professor might have explained to you the idea of a monotone function, or (in one direction) a nondecreasing function....
Search Engine Retrieval
I want to talk about the high level concept of what a search engine does. And I don’t mean like, Google, or Kagi, “the product,” but the technical object...
Nonograms
Hello! I hope you are having a lovely day. This week I got distracted by some non-database content and it consequently took up a lot of my time. Usually I...
Edge Contractions and Join Planning
The join graph of a query has a vertex for each relation and an edge between any two relations that have a predicate between them. For example, this query:...
Building One to Throw Away
I've been thinking lately about the nature of bespoke data structures for bespoke purposes. I think you learn fairly early on in most programming contexts...
Kicking the Tires on CedarDB's SQL
Last week it was my birthday and I had a bunch of stuff going on over the weekend so a short and simple post this week! If you are a database sicko (and I...
Multiplexing
In the world of electronics, multiplexing is the process of taking a set of communication channels and collapsing them all to be transmitted along a single...
How To Understand That Jepsen Report
There is a new Jepsen report which, as always, is an entertaining read and gives some insight into the way things might be broken in subtle ways. I learned...
