Narek Galstyan

SELECT 1 Touches 5,583 Lines of Postgres Source Code

Mon, 10 Nov 2025 22:37:04 -0500

I ran SELECT 1 in Postgres under gdb and traced the execution path through the source code.

But before that, a few words on why I wanted to know.

Background

A while back, I had run into an obscure bug in Postgres that I am sure has affected no one and will affect no one, due to the absurdity of its necessary conditions. I had tried to fix it and failed at the time. Recently I revisited the bug and again failed to find the root cause, despite spending many many hours deep in Postgres source code. Though I learned a little more about Postgres in the process (e.g., how it implements re-parenting heap-allocated memory when the memory needs to live longer than the context in which it was allocated), I came away empty-handed.

My Failed Attempts at Fixing an Obscure Postgres Bug

Sat, 19 Oct 2024 18:49:33 -0500

Note: This is an unfinished bug hunt with no satisfying conclusion. I am documenting what I know so far to hopefully finish solving this later.

Background

When building bm25 indexing for LanternDB, I came across a very obscure Postgres bug (which I reported in the pgsql-bugs mailing list). The bug causes a valid PL/pgSQL function call to fail, likely because of some faulty cache invalidation code path. I would be very surprised if this has ever affected anyone. If it has, please let me know! But as someone who has a history of obsession with bugs¹, I was intrigued and wanted to get to the root of the problem and fix it.

Recompiling Rust libcore to enable gated features

Wed, 01 Jul 2020 00:00:00 +0000

I have recently been working on a WebAssembly project in which I wanted to take advantage of SIMD (single instruction multiple data) instructions in WebAssembly that are now supported in modern browsers. I was using Rust for programming and due to this project discovered some peculiarities of Rust standard library that I’d like to share.

In Rust, wasm32 SIMD intrinsics are documented here. You can see in the source code of the module that the API it provides is feature-gated with wasm_target_feature and simd128. Normally, you could just add the respective feature flag(+simd128) to RUSTFLAGS and enable these. But to my surprise, adding relevant rustflags did not make the API available to me.

Parallel mandelbrot set visualization with WebAssembly, Raynon and Rust

Thu, 25 Jun 2020 22:12:31 -0700

Each color band represents the work of a particular thread

I built an interactive Mandelbrot set visualizer in Rust that paralellizes computation with Rayon and compiles to WebAssembly to run in your browser. Explore the Demo Here (Works on a recent version of Chrome.)

Or follow one of the direct links into particular areas of the mandelbrot world map below:

Near the weist of mandelbrot

Upper East side

Zoomed in from the one above