rename `Relation#uniq` to `Relation#distinct`. `#uniq` still works.

The similarity of `Relation#uniq` to `Array#uniq` is confusing. Since our
Relation API is close to SQL terms I renamed `#uniq` to `#distinct`.

There is no deprecation. `#uniq` and `#uniq!` are aliases and will continue
to work. I also updated the documentation to promote the use of `#distinct`.

21 files changed, 80 insertions, 40 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index f73fc9d9a3..37be191e0c 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,12 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Rename `Relation#uniq` to `Relation#distinct`. `#uniq` is still
+    available as an alias but we encourage to use `#distinct` instead.
+    Also `Relation#uniq_value` is aliased to `Relation#distinct_value`,
+    this is a temporary solution and you should migrate to `distinct_value`.
+
+    *Yves Senn*
+
 *   Fix quoting for sqlite migrations using copy_table_contents() with binary
     columns.
 
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index 06da5f2e0d..0c670bdaa1 100644
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -241,6 +241,7 @@ module ActiveRecord
     #   others.destroy_all                |   X   |    X     |    X
     #   others.find(*args)                |   X   |    X     |    X
     #   others.exists?                    |   X   |    X     |    X
+    #   others.distinct                   |   X   |    X     |    X
     #   others.uniq                       |   X   |    X     |    X
     #   others.reset                      |   X   |    X     |    X
     #
diff --git a/activerecord/lib/active_record/associations/collection_association.rb b/activerecord/lib/active_record/associations/collection_association.rb
index c992f51dbb..552f7f1117 100644
--- a/activerecord/lib/active_record/associations/collection_association.rb
+++ b/activerecord/lib/active_record/associations/collection_association.rb
@@ -174,7 +174,7 @@ module ActiveRecord
 
           reflection.klass.count_by_sql(custom_counter_sql)
         else
-          if association_scope.uniq_value
+          if association_scope.distinct_value
             # This is needed because 'SELECT count(DISTINCT *)..' is not valid SQL.
             column_name ||= reflection.klass.primary_key
             count_options[:distinct] = true
@@ -246,14 +246,14 @@ module ActiveRecord
       # +count_records+, which is a method descendants have to provide.
       def size
         if !find_target? || loaded?
-          if association_scope.uniq_value
+          if association_scope.distinct_value
             target.uniq.size
           else
             target.size
           end
         elsif !loaded? && !association_scope.group_values.empty?
           load_target.size
-        elsif !loaded? && !association_scope.uniq_value && target.is_a?(Array)
+        elsif !loaded? && !association_scope.distinct_value && target.is_a?(Array)
           unsaved_records = target.select { |r| r.new_record? }
           unsaved_records.size + count_records
         else
@@ -306,12 +306,13 @@ module ActiveRecord
         end
       end
 
-      def uniq
+      def distinct
         seen = {}
         load_target.find_all do |record|
           seen[record.id] = true unless seen.key?(record.id)
         end
       end
+      alias uniq distinct
 
       # Replace this collection with +other_array+. This will perform a diff
       # and delete/add only records that have changed.
@@ -352,7 +353,7 @@ module ActiveRecord
         callback(:before_add, record)
         yield(record) if block_given?
 
-        if association_scope.uniq_value && index = @target.index(record)
+        if association_scope.distinct_value && index = @target.index(record)
           @target[index] = record
         else
           @target << record
diff --git a/activerecord/lib/active_record/associations/collection_proxy.rb b/activerecord/lib/active_record/associations/collection_proxy.rb
index 543204abac..c2add32aa6 100644
--- a/activerecord/lib/active_record/associations/collection_proxy.rb
+++ b/activerecord/lib/active_record/associations/collection_proxy.rb
@@ -649,11 +649,12 @@ module ActiveRecord
       #   #      #<Pet name: "Fancy-Fancy">
       #   #    ]
       #
-      #   person.pets.select(:name).uniq
+      #   person.pets.select(:name).distinct
       #   # => [#<Pet name: "Fancy-Fancy">]
-      def uniq
-        @association.uniq
+      def distinct
+        @association.distinct
       end
+      alias uniq distinct
 
       # Count all records using SQL.
       #
diff --git a/activerecord/lib/active_record/associations/preloader/has_many_through.rb b/activerecord/lib/active_record/associations/preloader/has_many_through.rb
index 9a662d3f53..38bc7ce7da 100644
--- a/activerecord/lib/active_record/associations/preloader/has_many_through.rb
+++ b/activerecord/lib/active_record/associations/preloader/has_many_through.rb
@@ -6,7 +6,7 @@ module ActiveRecord
 
         def associated_records_by_owner
           super.each do |owner, records|
-            records.uniq! if reflection_scope.uniq_value
+            records.uniq! if reflection_scope.distinct_value
           end
         end
       end
diff --git a/activerecord/lib/active_record/querying.rb b/activerecord/lib/active_record/querying.rb
index e04a3d0976..902fd90c54 100644
--- a/activerecord/lib/active_record/querying.rb
+++ b/activerecord/lib/active_record/querying.rb
@@ -8,7 +8,7 @@ module ActiveRecord
     delegate :find_each, :find_in_batches, :to => :all
     delegate :select, :group, :order, :except, :reorder, :limit, :offset, :joins,
              :where, :preload, :eager_load, :includes, :from, :lock, :readonly,
-             :having, :create_with, :uniq, :references, :none, :to => :all
+             :having, :create_with, :uniq, :distinct, :references, :none, :to => :all
     delegate :count, :average, :minimum, :maximum, :sum, :calculate, :pluck, :ids, :to => :all
 
     # Executes a custom SQL query against your database and returns all the results. The results will
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index ad54ba55b6..50723b4848 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -10,7 +10,7 @@ module ActiveRecord
                             :extending]
 
     SINGLE_VALUE_METHODS = [:limit, :offset, :lock, :readonly, :from, :reordering,
-                            :reverse_order, :uniq, :create_with]
+                            :reverse_order, :distinct, :create_with]
 
     VALUE_METHODS = MULTI_VALUE_METHODS + SINGLE_VALUE_METHODS
 
@@ -506,6 +506,12 @@ module ActiveRecord
       includes_values & joins_values
     end
 
+    # +uniq+ and +uniq!+ are silently deprecated. +uniq_value+ delegates to +distinct_value+
+    # to maintain backwards compatibility. Use +distinct_value+ instead.
+    def uniq_value
+      distinct_value
+    end
+
     # Compares two relations for equality.
     def ==(other)
       case other
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 7f95181c67..6fedfefdee 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -198,8 +198,8 @@ module ActiveRecord
     def perform_calculation(operation, column_name, options = {})
       operation = operation.to_s.downcase
 
-      # If #count is used in conjuction with #uniq it is considered distinct. (eg. relation.uniq.count)
-      distinct = options[:distinct] || self.uniq_value
+      # If #count is used with #distinct / #uniq it is considered distinct. (eg. relation.distinct.count)
+      distinct = options[:distinct] || self.distinct_value
 
       if operation == "count"
         column_name ||= (select_for_count || :all)
diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index b7960936cf..10a31109d5 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -710,20 +710,22 @@ module ActiveRecord
     #   User.select(:name)
     #   # => Might return two records with the same name
     #
-    #   User.select(:name).uniq
-    #   # => Returns 1 record per unique name
+    #   User.select(:name).distinct
+    #   # => Returns 1 record per distinct name
     #
-    #   User.select(:name).uniq.uniq(false)
+    #   User.select(:name).distinct.distinct(false)
     #   # => You can also remove the uniqueness
-    def uniq(value = true)
-      spawn.uniq!(value)
+    def distinct(value = true)
+      spawn.distinct!(value)
     end
+    alias uniq distinct
 
-    # Like #uniq, but modifies relation in place.
-    def uniq!(value = true) # :nodoc:
-      self.uniq_value = value
+    # Like #distinct, but modifies relation in place.
+    def distinct!(value = true) # :nodoc:
+      self.distinct_value = value
       self
     end
+    alias uniq! distinct!
 
     # Used to extend a scope with additional methods, either through
     # a module or through a block provided.
@@ -814,7 +816,7 @@ module ActiveRecord
 
       build_select(arel, select_values.uniq)
 
-      arel.distinct(uniq_value)
+      arel.distinct(distinct_value)
       arel.from(build_from) if from_value
       arel.lock(lock_value) if lock_value
 
diff --git a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
index 1b1b479f1a..84bdca3a97 100644
--- a/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
+++ b/activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb
@@ -316,7 +316,7 @@ class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase
     dev.projects << projects(:active_record)
 
     assert_equal 3, dev.projects.size
-    assert_equal 1, dev.projects.uniq.size
+    assert_equal 1, dev.projects.distinct.size
   end
 
   def test_uniq_before_the_fact
diff --git a/activerecord/test/cases/associations/join_model_test.rb b/activerecord/test/cases/associations/join_model_test.rb
index 10ec33be75..c05481dd91 100644
--- a/activerecord/test/cases/associations/join_model_test.rb
+++ b/activerecord/test/cases/associations/join_model_test.rb
@@ -397,14 +397,14 @@ class AssociationsJoinModelTest < ActiveRecord::TestCase
   end
 
   def test_has_many_through_polymorphic_has_many
-    assert_equal taggings(:welcome_general, :thinking_general), authors(:david).taggings.uniq.sort_by { |t| t.id }
+    assert_equal taggings(:welcome_general, :thinking_general), authors(:david).taggings.distinct.sort_by { |t| t.id }
   end
 
   def test_include_has_many_through_polymorphic_has_many
     author            = Author.includes(:taggings).find authors(:david).id
     expected_taggings = taggings(:welcome_general, :thinking_general)
     assert_no_queries do
-      assert_equal expected_taggings, author.taggings.uniq.sort_by { |t| t.id }
+      assert_equal expected_taggings, author.taggings.distinct.sort_by { |t| t.id }
     end
   end
 
diff --git a/activerecord/test/cases/associations/nested_through_associations_test.rb b/activerecord/test/cases/associations/nested_through_associations_test.rb
index e355ed3495..e75d43bda8 100644
--- a/activerecord/test/cases/associations/nested_through_associations_test.rb
+++ b/activerecord/test/cases/associations/nested_through_associations_test.rb
@@ -410,7 +410,7 @@ class NestedThroughAssociationsTest < ActiveRecord::TestCase
 
     # Mary and Bob both have posts in misc, but they are the only ones.
     authors = Author.joins(:similar_posts).where('posts.id' => posts(:misc_by_bob).id)
-    assert_equal [authors(:mary), authors(:bob)], authors.uniq.sort_by(&:id)
+    assert_equal [authors(:mary), authors(:bob)], authors.distinct.sort_by(&:id)
 
     # Check the polymorphism of taggings is being observed correctly (in both joins)
     authors = Author.joins(:similar_posts).where('taggings.taggable_type' => 'FakeModel')
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index 9c73e4ca00..6f8290bdc3 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -1499,6 +1499,12 @@ class BasicsTest < ActiveRecord::TestCase
     assert_equal scope, Bird.uniq
   end
 
+  def test_distinct_delegates_to_scoped
+    scope = stub
+    Bird.stubs(:all).returns(mock(:distinct => scope))
+    assert_equal scope, Bird.distinct
+  end
+
   def test_table_name_with_2_abstract_subclasses
     assert_equal "photos", Photo.table_name
   end
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index be49e948fc..443a09f259 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -341,7 +341,8 @@ class CalculationsTest < ActiveRecord::TestCase
     assert_equal 5, Account.count(:firm_id)
   end
 
-  def test_count_with_uniq
+  def test_count_with_distinct
+    assert_equal 4, Account.select(:credit_limit).distinct.count
     assert_equal 4, Account.select(:credit_limit).uniq.count
   end
 
diff --git a/activerecord/test/cases/finder_test.rb b/activerecord/test/cases/finder_test.rb
index a9fa107749..e505fe9f18 100644
--- a/activerecord/test/cases/finder_test.rb
+++ b/activerecord/test/cases/finder_test.rb
@@ -82,7 +82,7 @@ class FinderTest < ActiveRecord::TestCase
 
   # ensures +exists?+ runs valid SQL by excluding order value
   def test_exists_with_order
-    assert Topic.order(:id).uniq.exists?
+    assert Topic.order(:id).distinct.exists?
   end
 
   def test_exists_with_includes_limit_and_empty_result
diff --git a/activerecord/test/cases/relation_test.rb b/activerecord/test/cases/relation_test.rb
index fd0b05cb77..9ca980fdf6 100644
--- a/activerecord/test/cases/relation_test.rb
+++ b/activerecord/test/cases/relation_test.rb
@@ -278,5 +278,17 @@ module ActiveRecord
       assert_equal [NullRelation], relation.extending_values
       assert relation.is_a?(NullRelation)
     end
+
+    test "distinct!" do
+      relation.distinct! :foo
+      assert_equal :foo, relation.distinct_value
+      assert_equal :foo, relation.uniq_value # deprecated access
+    end
+
+    test "uniq! was replaced by distinct!" do
+      relation.uniq! :foo
+      assert_equal :foo, relation.distinct_value
+      assert_equal :foo, relation.uniq_value # deprecated access
+    end
   end
 end
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 26cbb03892..3de2c6ab58 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -492,6 +492,7 @@ class RelationTest < ActiveRecord::TestCase
     expected_taggings = taggings(:welcome_general, :thinking_general)
 
     assert_no_queries do
+      assert_equal expected_taggings, author.taggings.distinct.sort_by { |t| t.id }
       assert_equal expected_taggings, author.taggings.uniq.sort_by { |t| t.id }
     end
 
@@ -1269,7 +1270,7 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal posts(:welcome),  comments(:greetings).post
   end
 
-  def test_uniq
+  def test_distinct
     tag1 = Tag.create(:name => 'Foo')
     tag2 = Tag.create(:name => 'Foo')
 
@@ -1277,11 +1278,14 @@ class RelationTest < ActiveRecord::TestCase
 
     assert_equal ['Foo', 'Foo'], query.map(&:name)
     assert_sql(/DISTINCT/) do
+      assert_equal ['Foo'], query.distinct.map(&:name)
       assert_equal ['Foo'], query.uniq.map(&:name)
     end
     assert_sql(/DISTINCT/) do
+      assert_equal ['Foo'], query.distinct(true).map(&:name)
       assert_equal ['Foo'], query.uniq(true).map(&:name)
     end
+    assert_equal ['Foo', 'Foo'], query.distinct(true).distinct(false).map(&:name)
     assert_equal ['Foo', 'Foo'], query.uniq(true).uniq(false).map(&:name)
   end
 
diff --git a/activerecord/test/models/author.rb b/activerecord/test/models/author.rb
index 8423411474..a96899ae10 100644
--- a/activerecord/test/models/author.rb
+++ b/activerecord/test/models/author.rb
@@ -30,8 +30,8 @@ class Author < ActiveRecord::Base
   has_many :comments_desc, -> { order('comments.id DESC') }, :through => :posts, :source => :comments
   has_many :limited_comments, -> { limit(1) }, :through => :posts, :source => :comments
   has_many :funky_comments, :through => :posts, :source => :comments
-  has_many :ordered_uniq_comments, -> { uniq.order('comments.id') }, :through => :posts, :source => :comments
-  has_many :ordered_uniq_comments_desc, -> { uniq.order('comments.id DESC') }, :through => :posts, :source => :comments
+  has_many :ordered_uniq_comments, -> { distinct.order('comments.id') }, :through => :posts, :source => :comments
+  has_many :ordered_uniq_comments_desc, -> { distinct.order('comments.id DESC') }, :through => :posts, :source => :comments
   has_many :readonly_comments, -> { readonly }, :through => :posts, :source => :comments
 
   has_many :special_posts
@@ -78,7 +78,7 @@ class Author < ActiveRecord::Base
   has_many :categories_like_general, -> { where(:name => 'General') }, :through => :categorizations, :source => :category, :class_name => 'Category'
 
   has_many :categorized_posts, :through => :categorizations, :source => :post
-  has_many :unique_categorized_posts, -> { uniq }, :through => :categorizations, :source => :post
+  has_many :unique_categorized_posts, -> { distinct }, :through => :categorizations, :source => :post
 
   has_many :nothings, :through => :kateggorisatons, :class_name => 'Category'
 
@@ -91,7 +91,7 @@ class Author < ActiveRecord::Base
   has_many :post_categories, :through => :posts, :source => :categories
   has_many :tagging_tags,    :through => :taggings, :source => :tag
 
-  has_many :similar_posts, -> { uniq }, :through => :tags, :source => :tagged_posts
+  has_many :similar_posts, -> { distinct }, :through => :tags, :source => :tagged_posts
   has_many :distinct_tags, -> { select("DISTINCT tags.*").order("tags.name") }, :through => :posts, :source => :tags
 
   has_many :tags_with_primary_key, :through => :posts
diff --git a/activerecord/test/models/book.rb b/activerecord/test/models/book.rb
index ce81a37966..5458a28cc9 100644
--- a/activerecord/test/models/book.rb
+++ b/activerecord/test/models/book.rb
@@ -2,7 +2,7 @@ class Book < ActiveRecord::Base
   has_many :authors
 
   has_many :citations, :foreign_key => 'book1_id'
-  has_many :references, -> { uniq }, :through => :citations, :source => :reference_of
+  has_many :references, -> { distinct }, :through => :citations, :source => :reference_of
 
   has_many :subscriptions
   has_many :subscribers, :through => :subscriptions
diff --git a/activerecord/test/models/liquid.rb b/activerecord/test/models/liquid.rb
index 6cfd443e75..69d4d7df1a 100644
--- a/activerecord/test/models/liquid.rb
+++ b/activerecord/test/models/liquid.rb
@@ -1,5 +1,4 @@
 class Liquid < ActiveRecord::Base
   self.table_name = :liquid
-  has_many :molecules, -> { uniq }
+  has_many :molecules, -> { distinct }
 end
-
diff --git a/activerecord/test/models/project.rb b/activerecord/test/models/project.rb
index 90273adafc..f893754b9f 100644
--- a/activerecord/test/models/project.rb
+++ b/activerecord/test/models/project.rb
@@ -1,11 +1,11 @@
 class Project < ActiveRecord::Base
-  has_and_belongs_to_many :developers, -> { uniq.order 'developers.name desc, developers.id desc' }
+  has_and_belongs_to_many :developers, -> { distinct.order 'developers.name desc, developers.id desc' }
   has_and_belongs_to_many :readonly_developers, -> { readonly }, :class_name => "Developer"
-  has_and_belongs_to_many :selected_developers, -> { uniq.select "developers.*" }, :class_name => "Developer"
+  has_and_belongs_to_many :selected_developers, -> { distinct.select "developers.*" }, :class_name => "Developer"
   has_and_belongs_to_many :non_unique_developers, -> { order 'developers.name desc, developers.id desc' }, :class_name => 'Developer'
   has_and_belongs_to_many :limited_developers, -> { limit 1 }, :class_name => "Developer"
-  has_and_belongs_to_many :developers_named_david, -> { where("name = 'David'").uniq }, :class_name => "Developer"
-  has_and_belongs_to_many :developers_named_david_with_hash_conditions, -> { where(:name => 'David').uniq }, :class_name => "Developer"
+  has_and_belongs_to_many :developers_named_david, -> { where("name = 'David'").distinct }, :class_name => "Developer"
+  has_and_belongs_to_many :developers_named_david_with_hash_conditions, -> { where(:name => 'David').distinct }, :class_name => "Developer"
   has_and_belongs_to_many :salaried_developers, -> { where "salary > 0" }, :class_name => "Developer"
 
   ActiveSupport::Deprecation.silence do