Leaflet-Hexbins is a powerful tool to aggregate data and visualize it quickly on a map. It can size the hexbin radius based on a feature values. But what if we used HyperLogLog data to preserve user-privacy? This post will provide a convenient way to quickly perform on-the-fly HyperLogLog unions for leaflet-hexbins. No more backend-constraint for HyperLogLog There are many HyperLogLog implementations out there but few work as well as postgres-hll and js-hll. They can even talk to each other by exchanging hexstrings! Usually postgres-hll is pretty much the standard extension to use, when dealing with HyperLogLog but is obviously bound to a postgres database running somewhere. With js-hll, the backend-constraint for HyperLogLog is gone, just so that users can perform any HyperLogLog action in their frontend!
HyperLogLog is a fantastic algorithm to quickly count distinct elements in a set. As it consumes few memory and is really fast, it's perfectly suited for big data. For a nice, visual explanation step over to the Redis guys on Youtube. However, this article is not about explaining HyperLogLog but rather understanding how to deal with backend/frontend communication between javascript and postgres by exchanging hexstrings between the two amazing libraries postgres-hll for postgres and js-hll for javascript.
Querying Postgres with Python Fastapi Backend and Leaflet & Geoman Fronted - Applying Geometry Filters How to query a database with a user-defined geometry drawn on a Leaflet frontend? A very common use case for map applications are custom filters. Either thematic, temporal or value-based filters play a significant role but probably in a geographical context the most dominant one might be spatial filtering. In this blog post, I describe a simple boilerplate setup based on postgres, fastapi and geoman.
