Pushing Values to Zero
There is a popular presentation of the exponential distribution that goes through the geometric distribution. The geometric distribution arises from flipping...
Linearity in Query Processing
I saw a fun post this week about interpreting colours as vectors and the way you can exploit that interpretation to nicely represent certain operations you...
The Relational Derivative Pt. 2: Groups are Good
Last week we talked about the notion of the relational derivative and its application to enforcing integrity constraints in databases. The relational...
Integrity Constraints and the Relational Derivative
In a SQL database, you can set up a foreign key with REFERENCES: nullbitmap=# CREATE TABLE ab (a INT PRIMARY KEY, b INT); CREATE TABLE nullbitmap=# INSERT...
The Two Machines
There's a joke in my friend circle that asks "is it a database?" A startup, a program, a syscall, a person good with numbers, a person with a good memory....
Benchmarks That Aren't Your Friends
We’ve now talked twice about an important dimension of a benchmark: the openness of the loop. While there’s more subtlety to it, if what you take away is:...
Measuring Throughput
Note: I'm trying out enabling comments. Behave! I reserve the right to disable them again for any reason including "the very idea of someone commenting made...
SQL's Grammar Ambiguity
I was going to write a longer, more involved post this week, but I wound up getting Covid and didn't have it in me to work through all the stuff I had to for...
Languages Without Abstraction
Implementing something like a compiler, there is the understanding that we want different representations of a program for different purposes. This is why we...
The Closed-Loop Benchmark Trap
Let's make a little mock database. It won't actually do anything but pretend to handle requests. I've had cause at work lately to write some Go so we're...
Some Books I Like // One Year of NULL BITMAP
This is the 52nd NULL BITMAP, which means I have been doing this for a whole year! I skipped one week before I decided that this was going to be a weekly...
Solving Rubik's Cubes with Computers
The first place I got into programming was making games. You can probably dig up some games I made long ago if you try hard enough (do not). In high school,...
What do we want? Negation! When do we want it? Not later!
Hello I am traveling this weekend! I am home in Ontario. I wanted to share this picture I took of this guy feeding a bear. Bear eating an object out of a...
A Query Planning Guideline
A number of readers last week reached out to direct my attention to What if a SQL Statement Returned a Database which is a much more thorough and well-...
Multiple Returns in SQL
Podcast Appearance I was on the Thinking About Computers podcast recently! We had a fun chat on the topic of writing technical content and research....
Deriving Functional Dependencies for Selections
Over the last two weeks you were babysat by the pre-scheduling feature of Buttondown, since I was away in Japan without my laptop. Here's me in Japan: I had...
To Understand Correctness, You Must First Understand Incorrectness
Recently I was in a Discord channel where someone wrote something akin to “I have a question about linearizability” which had an attached thread with 80...
Physical Properties #4
Previous parts of this series: Physical Properties #1 Physical Properties #2 Physical Properties #3 Relational query planning makes a distinction between...
In Codd we Trust (or not)
Get in loser, we’re doing another Codd philosophizing session. Codd’s paper introducing the relational model opens up like so: Future users of large data...
NULL BITMAP Builds a Database #2: Enter the Memtable
I didn't realize how hard it would be to bin-pack episodes of this thing into the roughly ~750 word chunks that I try to keep issues of this newsletter at....
