deprecate `Relation#uniq` use `Relation#distinct` instead.

See #9683 for the reasons we switched to `distinct`.

Here is the discussion that triggered the actual deprecation #20198.

`uniq`, `uniq!` and `uniq_value` are still around.
They will be removed in the next minor release after Rails 5.

3 files changed, 5 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index a3c30642d0..779a3fbbbd 100644
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -266,7 +266,6 @@ module ActiveRecord
     #   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
     #
     # === Overriding generated methods
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 85648a7f8f..7d37313058 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -9,7 +9,7 @@ module ActiveRecord
                             :extending, :unscope]
 
     SINGLE_VALUE_METHODS = [:limit, :offset, :lock, :readonly, :reordering,
-                            :reverse_order, :distinct, :create_with, :uniq]
+                            :reverse_order, :distinct, :create_with]
     CLAUSE_METHODS = [:where, :having, :from]
     INVALID_METHODS_FOR_DELETE_ALL = [:limit, :distinct, :offset, :group, :having]
 
@@ -618,6 +618,7 @@ module ActiveRecord
     def uniq_value
       distinct_value
     end
+    deprecate uniq_value: :distinct_value
 
     # Compares two relations for equality.
     def ==(other)
diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index 69ce5cdc2a..fd78db2e95 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -587,7 +587,7 @@ module ActiveRecord
     #
     # The two relations must be structurally compatible: they must be scoping the same model, and
     # they must differ only by +where+ (if no +group+ has been defined) or +having+ (if a +group+ is
-    # present). Neither relation may have a +limit+, +offset+, or +uniq+ set.
+    # present). Neither relation may have a +limit+, +offset+, or +distinct+ set.
     #
     #    Post.where("id = 1").or(Post.where("id = 2"))
     #    # SELECT `posts`.* FROM `posts`  WHERE (('id = 1' OR 'id = 2'))
@@ -790,6 +790,7 @@ module ActiveRecord
       spawn.distinct!(value)
     end
     alias uniq distinct
+    deprecate uniq: :distinct
 
     # Like #distinct, but modifies relation in place.
     def distinct!(value = true) # :nodoc:
@@ -797,6 +798,7 @@ module ActiveRecord
       self
     end
     alias uniq! distinct!
+    deprecate uniq!: :distinct!
 
     # Used to extend a scope with additional methods, either through
     # a module or through a block provided.