Extracting information about the shape of rails models and data
  • Often when diving into a new codebase or set of codebases the data model is the best way to get a sense for what's going on. But if it's been around for a while there'll be quite a few models that are no longer in use, models that use STI, and if it's part of a larger system, models that read/write to a different database with establish_connection. I like to be able put all models in a big spreadsheet where I can 1. Sort by updated_at to see which ones are no longer in use, and 2. Order by name and read down through them one by one. This snippet, run from a rails command line, helps me do that.

  • Main Snippet

  • errors = []
    models_and_databases = ActiveRecord::Base.descendants.map do |model|
        connection_spec = model.connection_pool.spec
        database_name = connection_spec.config[:database] || 'Unknown'
        table_name = model.table_name
          # Check if the model's table has an 'updated_at' column
          if model.column_names.include?('updated_at')
            # Fetch the latest updated_at value
            last_updated = model.order(updated_at: :desc).limit(1).pluck(:updated_at).first
            last_updated = nil
        rescue => e
          last_updated = nil
        [model.name, { database: database_name, table: table_name, last_updated: last_updated }]
      rescue => e
        errors << "Error processing model: #{model.name}"
        errors << "Error message: #{e.message}"
  • Print out the hash

  • models_and_databases.each do |model_name, details|
      puts "#{model_name}, #{details[:table]}, #{details[:database]}, #{details[:last_updated]}"
  • To add this to an airtable:

    • Copy paste it into a new text file

    • Do a find and replace for , - replace all occurences with the tab character.

    • Copy and paste this into an airtable with the relevant 4 columns

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