From a19e79859dd51147cfe1ca5c2f709c82eb6339b6 Mon Sep 17 00:00:00 2001
From: Aidan Feldman <aidan.feldman@gmail.com>
Date: Thu, 30 May 2013 04:10:32 -0400
Subject: [PATCH] add `mongoid:remove_undefined_indexes` rake task

removes indexes that exist in the database but aren't specified on the
models
---
 lib/mongoid/railties/database.rake |  6 ++++
 lib/rails/mongoid.rb               | 47 ++++++++++++++++++++++++++++
 spec/rails/mongoid_spec.rb         | 49 ++++++++++++++++++++++++++++++
 3 files changed, 102 insertions(+)

diff --git a/lib/mongoid/railties/database.rake b/lib/mongoid/railties/database.rake
index cf69e23fa35..862cbf0793d 100644
--- a/lib/mongoid/railties/database.rake
+++ b/lib/mongoid/railties/database.rake
@@ -72,6 +72,12 @@ namespace :db do
       ::Rails::Mongoid.create_indexes
     end
 
+    desc "Remove indexes that exist in the database but aren't specified on the models"
+    task :remove_undefined_indexes => :environment do
+      ::Rails.application.eager_load!
+      ::Rails::Mongoid.remove_undefined_indexes
+    end
+
     desc "Remove the indexes defined on your mongoid models without questions!"
     task :remove_indexes => :environment do
       ::Rails.application.eager_load!
diff --git a/lib/rails/mongoid.rb b/lib/rails/mongoid.rb
index 5b8909ec5b8..4b7e205059a 100644
--- a/lib/rails/mongoid.rb
+++ b/lib/rails/mongoid.rb
@@ -29,6 +29,53 @@ def create_indexes
       end.compact
     end
 
+    # Return the list of indexes by model that exist in the database but aren't
+    # specified on the models.
+    #
+    # @example Return the list of unused indexes.
+    #   Rails::Mongoid.undefined_indexes
+    #
+    # @return Hash{Class => Array(Hash)} The list of undefined indexes by model.
+    def undefined_indexes
+      undefined_by_model = {}
+
+      ::Mongoid.models.each do |model|
+        unless model.embedded?
+          model.collection.indexes.each do |index|
+            # ignore default index
+            unless index['name'] == '_id_'
+              key = index['key'].symbolize_keys
+              spec = model.index_specification(key)
+              unless spec
+                # index not specified
+                undefined_by_model[model] ||= []
+                undefined_by_model[model] << index
+              end
+            end
+          end
+        end
+      end
+
+      undefined_by_model
+    end
+
+    # Remove indexes that exist in the database but aren't specified on the
+    # models.
+    #
+    # @example Remove undefined indexes.
+    #   Rails::Mongoid.remove_undefined_indexes
+    #
+    # @return Hash{Class => Array(Hash)} The list of indexes that were removed by model.
+    def remove_undefined_indexes
+      undefined_indexes.each do |model, indexes|
+        indexes.each do |index|
+          key = index['key'].symbolize_keys
+          model.collection.indexes.drop(key)
+          logger.info("MONGOID: Removing index: #{index['name']} on #{model}.")
+        end
+      end
+    end
+
     # Remove indexes for each model given the provided globs and the class is
     # not embedded.
     #
diff --git a/spec/rails/mongoid_spec.rb b/spec/rails/mongoid_spec.rb
index 57b9fe8e8b6..f186aaaf1ab 100644
--- a/spec/rails/mongoid_spec.rb
+++ b/spec/rails/mongoid_spec.rb
@@ -72,6 +72,55 @@
     end
   end
 
+  describe ".undefined_indexes" do
+
+    before(:each) do
+      Rails::Mongoid.create_indexes
+    end
+
+    subject do
+      Rails::Mongoid.undefined_indexes
+    end
+
+    it { should eq({}) }
+
+    context "with extra index on model collection" do
+      before(:each) do
+        User.collection.indexes.create(account_expires: 1)
+      end
+
+      its(:keys) { should eq([User]) }
+
+      it "should have single index returned" do
+        names = subject[User].map{ |index| index['name'] }
+        expect(names).to eq(['account_expires_1'])
+      end
+    end
+  end
+
+  describe ".remove_undefined_indexes" do
+
+    let(:logger) do
+      stub
+    end
+
+    let(:indexes) do
+      User.collection.indexes
+    end
+
+    before(:each) do
+      Rails::Mongoid.create_indexes
+      indexes.create(account_expires: 1)
+      Rails::Mongoid.remove_undefined_indexes
+    end
+
+    subject do
+      Rails::Mongoid.undefined_indexes
+    end
+
+    it { should eq({}) }
+  end
+
   describe ".remove_indexes" do
 
     let(:logger) do