Question

Is there a gem or plugin like https://github.com/eladmeidar/rails_indexes that works for rails3?

Answer 1

You can paste following code in your console to know the missing foreign key indexes. This, however, is not as capable of the plugin that you refer to. It only searches for rails style foreign keys that have an _id at the end of their column name.

c = ActiveRecord::Base.connection
c.tables.collect do |t|  
  columns = c.columns(t).collect(&:name).select {|x| x.ends_with?("_id") || x.ends_with?("_type")}
  indexed_columns = c.indexes(t).collect(&:columns).flatten.uniq
  unindexed = columns - indexed_columns
  unless unindexed.empty?
    puts "#{t}: #{unindexed.join(", ")}"
  end
end

Source