Week 2 at the Recurse Center

June 6, 2017

Another week, another update.

This week

I surprised myself by only working on the database project.1 I’m not sure I’ve ever spent so much concentrated time focused on a single project of my own like this – even in college I always had a couple of different things I had to be working on. It’s kind of addictive, but I also worry that it will quickly become exhausting.

I focused this week on implementing better data structures for the database index. I spent about a day working on understanding how B-trees work, with some help from Knuth’s volume 3, Sorting and Searching.[^knuth] Based on that I was able to implement an immutable B-tree in Rust where inserting an element returns a reference to a new tree that shares structure with the old one. The next day Josh helped me find a bunch of bugs in my implementation (only off-by-one errors of various sorts, thanks to Rust’s type system), and we were able to swap out the standard library’s B-tree set for the custom implementation without breaking the query engine. We also made some ergonomic improvements to the CLI, so it’s now sort of usable!

On Friday I started looking at how to persist the nodes of the B-tree to disk, which is the hard part. Datomic, which I’m basing my design on, outsources that work to other databases, using something like Postgresql, DynamoDB or Cassandra as a key-value store for blobs of binary data. For now at least I’m planning to do the same, so the main things I have to deal with are serializing the tree and adapting the B-tree insert and search algorithms to work when each node must be fetched from disk. (For performance the nodes can be cached since they’re immutable, but the worst-case is always a disk fetch.)


Last week I promised myself a post about my Recurse Center goals. A lot of them are things I want to try to do while I’m here, but others are warnings to myself of things to watch out for:

Come away with a basic, working implementation of my database. A good barometer here might be, can you implement a toy Twitter with it? I have a bunch of sub-goals for the database that I’ll cover in a different post, but they mostly boil down to features of Datomic I want to implement.

Pair on someone else’s substantial project. So far I’ve been working almost entirely on my own thing, and while I’ve done some pairing on it I still feel like I’d learn more by sometimes working with someone else on something they want to do.

Take advantage of being in the RC community. It’s an incredibly rich opportunity to meet people and learn things I didn’t know I didn’t know, so I want to keep my eyes open for opportunities to do that and say yes to them. The capture the flag challenge in week 1 was a good example of this.

Learn more about networking. I think this is one of the areas where my programming knowledge is most shallow, and I’d like to work on something that involves some low-level networking – maybe a peer-to-peer or UDP-based project. The database will involve a little bit of this but not a ton, I think, so another small project or two would be nice.

Write blog posts about interesting things I learn. These weekly updates are good, but I’d also like to do more in-depth and one-off posts about things I’m learning or working on. One I might do soon is on implementing an iterator in Rust using an algorithm that would normally be recursive, which was not straightforward for me.

Stay excited about programming. Often my enthusiasm for programming runs in cycles. I’ll get obsessed with a project or an idea, work on it with most of my free time for a week or two, and then burn out and not do anything for a while. I’d like to practice sustaining that kind of excitement over a longer period while still carving out time for socializing, taking care of myself, and pursuing other interests like writing.

Speaking of which, take care of myself. Eat well and exercise. I’m used to working remotely, where it’s a little easier to do these things, not to mention the difference between checking out of work at the end of the day and putting my personal project down just for a little while. But this is really important – I’ll be much happier, more fulfilled and more productive if I carve out time to cook myself dinner and go for a run now and then. This is something I haven’t been doing well the last two weeks, which is not the end of the world but is something to watch out for.

  1. I’ll write a post about what this is exactly and why I think it’s interesting soon, I think. [^knuth]: The book turned out to be both approachable and a great conversation-starter – people kept asking me what I was working on that required me to read that. If you want to make friends with Recursers, apparently carrying around a copy of Knuth is the way to go.