The most efficient RANDOM query in Rails!

RandomRails: fast random records for ActiveRecord

Picking random rows sounds simple, but the usual approach (ORDER BY RANDOM() / ORDER BY RAND()) gets painfully slow as tables grow because the database has to assign a random value to every row and sort the full result set. 😅

RandomRails is a gem that provides a Model.random API and automatically selects an efficient strategy based on your database and table size (supports PostgreSQL, MySQL, and SQLite).

How it stays fast

• PostgreSQL: uses TABLESAMPLE BERNOULLI for large tables (10k+ by default), and falls back to offset-based sampling for smaller ones
• MySQL / SQLite: efficient offset-based sampling, with graceful fallbacks when needed
• Auto selection: avoids full-table sorting whenever possible
• Configurable: thresholds, precision, and table-size caching via an initializer

Benchmarks (10 runs each)

In real-world tests on a users table, User.random beat ORDER BY RANDOM() by ~2× to ~32×, and the advantage grows with table size (e.g. ~3.84s → ~0.22s at 1k rows, and ~171.5s → ~5.34s at 1M rows).

Install + usage

# Gemfile
gem "random-rails"

User.random
User.random(count: 5)
User.where(active: true).random(count: 3)

https://github.com/the-rubies-way/random-rails