Merge branch 'master' into nested_has_many_through

5 files changed, 20 insertions, 10 deletions

diff --git a/activerecord/lib/active_record/associations/singular_association.rb b/activerecord/lib/active_record/associations/singular_association.rb
index 0d8e45adb5..4edbe216be 100644
--- a/activerecord/lib/active_record/associations/singular_association.rb
+++ b/activerecord/lib/active_record/associations/singular_association.rb
@@ -37,7 +37,7 @@ module ActiveRecord
 
         # Implemented by subclasses
         def replace(record)
-          raise NotImplementedError
+          raise NotImplementedError, "Subclasses must implement a replace(record) method"
         end
 
         def set_new_record(record)
diff --git a/activerecord/lib/active_record/locking/optimistic.rb b/activerecord/lib/active_record/locking/optimistic.rb
index 6b2b1ebafe..9a31675782 100644
--- a/activerecord/lib/active_record/locking/optimistic.rb
+++ b/activerecord/lib/active_record/locking/optimistic.rb
@@ -23,7 +23,7 @@ module ActiveRecord
     #   p2.first_name = "should fail"
     #   p2.save # Raises a ActiveRecord::StaleObjectError
     #
-    # Optimistic locking will also check for stale data when objects are destroyed.  Example:
+    # Optimistic locking will also check for stale data when objects are destroyed. Example:
     #
     #   p1 = Person.find(1)
     #   p2 = Person.find(1)
diff --git a/activerecord/lib/active_record/locking/pessimistic.rb b/activerecord/lib/active_record/locking/pessimistic.rb
index 557b277d6b..862cf8f72a 100644
--- a/activerecord/lib/active_record/locking/pessimistic.rb
+++ b/activerecord/lib/active_record/locking/pessimistic.rb
@@ -9,9 +9,8 @@ module ActiveRecord
     #   Account.find(1, :lock => true)
     #
     # Pass <tt>:lock => 'some locking clause'</tt> to give a database-specific locking clause
-    # of your own such as 'LOCK IN SHARE MODE' or 'FOR UPDATE NOWAIT'.
+    # of your own such as 'LOCK IN SHARE MODE' or 'FOR UPDATE NOWAIT'. Example:
     #
-    # Example:
     #   Account.transaction do
     #     # select * from accounts where name = 'shugo' limit 1 for update
     #     shugo = Account.where("name = 'shugo'").lock(true).first
@@ -24,6 +23,7 @@ module ActiveRecord
     #
     # You can also use ActiveRecord::Base#lock! method to lock one record by id.
     # This may be better if you don't need to lock every row. Example:
+    #
     #   Account.transaction do
     #     # select * from accounts where ...
     #     accounts = Account.where(...).all
@@ -44,7 +44,7 @@ module ActiveRecord
     module Pessimistic
       # Obtain a row lock on this record. Reloads the record to obtain the requested
       # lock. Pass an SQL locking clause to append the end of the SELECT statement
-      # or pass true for "FOR UPDATE" (the default, an exclusive row lock).  Returns
+      # or pass true for "FOR UPDATE" (the default, an exclusive row lock). Returns
       # the locked record.
       def lock!(lock = true)
         reload(:lock => lock) if persisted?
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 5af20bf38b..371403f510 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -110,7 +110,10 @@ module ActiveRecord
 
     # Returns true if there are no records.
     def empty?
-      loaded? ? @records.empty? : count.zero?
+      return @records.empty? if loaded?
+
+      c = count
+      c.respond_to?(:zero?) ? c.zero? : c.empty?
     end
 
     def any?
diff --git a/activerecord/lib/active_record/validations/uniqueness.rb b/activerecord/lib/active_record/validations/uniqueness.rb
index a96796f9ff..9cd6c26322 100644
--- a/activerecord/lib/active_record/validations/uniqueness.rb
+++ b/activerecord/lib/active_record/validations/uniqueness.rb
@@ -173,10 +173,17 @@ module ActiveRecord
       # This technique is also known as optimistic concurrency control:
       # http://en.wikipedia.org/wiki/Optimistic_concurrency_control
       #
-      # Active Record currently provides no way to distinguish unique
-      # index constraint errors from other types of database errors, so you
-      # will have to parse the (database-specific) exception message to detect
-      # such a case.
+      # The bundled ActiveRecord::ConnectionAdapters distinguish unique index
+      # constraint errors from other types of database errors by throwing an
+      # ActiveRecord::RecordNotUnique exception.
+      # For other adapters you will have to parse the (database-specific) exception
+      # message to detect such a case.
+      # The following bundled adapters throw the ActiveRecord::RecordNotUnique exception:
+      # * ActiveRecord::ConnectionAdapters::MysqlAdapter
+      # * ActiveRecord::ConnectionAdapters::Mysql2Adapter
+      # * ActiveRecord::ConnectionAdapters::SQLiteAdapter
+      # * ActiveRecord::ConnectionAdapters::SQLite3Adapter
+      # * ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
       #
       def validates_uniqueness_of(*attr_names)
         validates_with UniquenessValidator, _merge_attributes(attr_names)