Posts tagged #performance

Why Postgres ignores your trigram index: sargability, UPPER(), and an ORM that rewrites your query

October 1, 202610 min

You add a pg_trgm GIN index, the substring query gets no faster, and EXPLAIN shows a sequential scan. The operator is usually not the problem: pg_trgm serves ILIKE from the index perfectly well. What breaks it is a function wrapped around the column, and on Django that function is one your ORM adds for you. Measured at four table sizes, with the three fixes and what each costs.

Finding the N+1 before it finds prod: the benchmark that couldn't fail

August 13, 20269 min

I wrote a benchmark to prove my vault API's eager loading worked, charted it, and published it. Five weeks later I deleted the eager loading from the viewset to watch the benchmark go red. Fifteen tests passed in 4.67 seconds and the benchmark cheerfully printed the same flat line.

A fast molecular-dynamics simulator in pure NumPy

June 25, 202611 min

A naive molecular-dynamics loop is O(N²) and dies past a few hundred particles. With cell lists, a cutoff Lennard-Jones potential, velocity-Verlet integration, and reduced units, you can simulate thousands of particles in pure NumPy and watch a gas equilibrate.