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debshots/README.md
Christoph Haas 4948fe50e3 Add semantic package search via pgvector embeddings 
Package text search now combines several strategies: exact name match,
name prefix promotion, compound word splitting ("sqlite browser" finds
"sqlitebrowser") and semantic nearest neighbor search over description
embeddings computed by an external embedding service (all-MiniLM-L6-v2,
384 dims) stored with the pgvector extension. Classic PostgreSQL
full-text search remains as fallback when the vector service is
unreachable. Gibberish queries without lexical overlap with the package
data return empty results instead of random matches.

Embeddings can be backfilled with bin/rails debshots:compute_vectors.

Also drops the unused lograge gem from the Gemfile.
2026-08-22 22:07:56 +02:00

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About debshots

Debshots is a web application written in Ruby-on-Rails that powers the screenshots.debian.net web site. Many services like packages.debian.net, Ubuntu Software or Synaptic rely on it.

State of the application

The code you find here resembles the version that is deployed to screenshots.debian.net. It has been refactored in 06/2024 to Rails 7. If you find strange or changed behavior please open an issue at https://salsa.debian.org/debian/debshots/-/issues

Development

Check out the doc/README.Development.md

Package search

The package search combines several strategies, tried in this order:

  1. Exact package name: Searching for vim shows exactly this package without calling any external service.
  2. Name prefix matches: Packages whose name starts with the query rank first, e.g. searching for sqlite promotes sqlite3, sqlitebrowser and friends above all other results.
  3. Compound word splitting: Packages whose name contains all query tokens match too, so sqlite browser finds sqlitebrowser.
  4. Semantic search: The query is embedded via the vector service (all-MiniLM-L6-v2, 384 dimensions) and the nearest neighbors among the package description embeddings are returned, using the pgvector extension with an HNSW cosine index. Embeddings are computed from the package description and long description and can be (re-)built with bin/rails debshots:compute_vectors.
  5. Full-text fallback: If the vector service cannot be reached, classic PostgreSQL full-text search takes over.

Queries that share no vocabulary with the package data (gibberish, keyboard mash) return an honest empty result instead of random semantic matches.

Deployment

Read the doc/README.Installation.md