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debshots/README.md

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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.

Why is this package in my results? Each result knows which search strategy produced it. The controller exposes this as @search_sources (a hash mapping package ids to :exact, :name_prefix, :name_contains, :semantic or :fulltext). For debugging you can render a small badge on every result card by adding show_sources=1 to the URL, e.g. https://screenshots.debian.net/packages?search=sqlite&show_sources=1.

Package pages also show semantically related packages, computed as a nearest neighbor query against the package's own description embedding - no external service call involved.

Deployment

Read the doc/README.Installation.md