benchmark_explain_active_record

🔍 Benchmark and Explain ActiveRecord Queries

When you need to squeeze out extra performance, combine Ruby’s Benchmark with ActiveRecord’s explain to measure and analyze query plans on the fly. This helps you catch slow joins, missing indexes, and N+1 problems without leaving the console.

require 'benchmark'

# Measure wall time for a complex query
ms = (Benchmark.realtime do
  users = User.includes(:posts, :comments)
              .where(active: true)
              .where('posts.created_at > ?', 1.week.ago)
              .to_a
end * 1000).round(1)
puts "Loaded #{users.size} users in #{ms}ms"

# Print the query plan
puts User.includes(:posts, :comments)
         .where(active: true)
         .where('posts.created_at > ?', 1.week.ago)
         .explain