FindDuplicates

This GEM allows you to find duplicate models with same value for a column, e.g.: Find all users with the same first name.

Just add 'find_duplicates' to your Gemfile, and you automatically enhance your AR models functionality.

Installation

Add this line to your application's Gemfile:

gem 'find_duplicates'

And then execute:

$ bundle

Or install it yourself as:

$ gem install find_duplicates

Usage

Given an AR model, for example User, with 'first_name' and 'last_name' fields:

class User < ActiveRecord::Base
  attr_accessible :first_name, :last_name
end

> @user1 = User.create first_name: 'Adam', last_name: 'Klein'
> @user2 = User.create first_name: 'Calvin', last_name: 'Klein'
> @user3 = User.create first_name: 'Adam', last_name: 'Sandler'

class methods:

> User.duplicates(:first_name)          # => [@user1, @user3]
> User.duplicates(:last_name)           # => [@user1, @user2]

also works with multiple fields:

> @user4 = User.create first_name: 'John', last_name: 'Major'
> @user5 = User.create first_name: 'John', last_name: 'Major'
> User.duplicates(:first_name, :last_name)         # => [@user4, @user5]
> User.duplicates([:first_name, :last_name])       # => [@user4, @user5]

instance methods:

> @user1.duplicate?(:first_name)             # => true
> @user1.duplicates(:first_name)             # => [@user3]
> @user1.duplicates_with_self(:last_name)    # => [@user1, @user2]

instance methods also work with multiple fields:

> @user1.duplicates_with_self(:first_name, :last_name)    # => []
> @user4.duplicates_with_self(:first_name, :last_name)    # => [@user4, @user5]

The underlying SQL

Just in case you were wondering. User.duplicates(:first_name, :last_name) results in:

"SELECT * FROM users JOIN ( SELECT first_name, last_name, count() as qty FROM users GROUP BY first_name, last_name HAVING count() > 1 ) t ON t.first_name = users.first_name AND t.last_name = users.last_name"

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request