https://github.com/rails/rails/pull/8240

gistfile1.diff

diff --git a/Gemfile b/Gemfile
index 1422da2..521b4da 100644
--- a/Gemfile
+++ b/Gemfile
@@ -38,7 +38,7 @@ group :test do
   end

   platforms :mri_19, :mri_20 do
-    gem 'debugger'
+    # gem 'debugger'
   end

   gem 'benchmark-ips'
@@ -55,7 +55,7 @@ platforms :ruby do
   gem 'sqlite3', '~> 1.3.6'

   group :db do
-    gem 'pg', '>= 0.11.0'
+#    gem 'pg', '>= 0.11.0'
     gem 'mysql', '>= 2.9.0'
     gem 'mysql2', '>= 0.3.13'
   end
diff --git a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
index e790f73..1587eae 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb
@@ -77,6 +77,14 @@ module ActiveRecord
         @connection.escape(string)
       end

+      def quoted_date(value)
+        if value.acts_like?(:time) && value.respond_to?(:usec)
+          "#{super}.#{sprintf("%06d", value.usec)}"
+        else
+          super
+        end
+      end
+
       # CONNECTION MANAGEMENT ====================================

       def active?
diff --git a/activerecord/test/cases/quoting_test.rb b/activerecord/test/cases/quoting_test.rb
index e2439b9..99ce92b 100644
--- a/activerecord/test/cases/quoting_test.rb
+++ b/activerecord/test/cases/quoting_test.rb
@@ -52,6 +52,11 @@ module ActiveRecord
         assert_equal t.to_s(:db), @quoter.quoted_date(t)
       end

+      def test_quoted_time_microseconds
+        t = Time.at(946684800.2123)
+        assert_equal "100000.212300", @quoter.quoted_date(t)
+      end
+
       def test_quoted_time_utc
         with_timezone_config default: :utc do
           t = Time.now