2 files changed, 49 insertions, 32 deletions

diff --git a/activerecord/test/cases/adapters/postgresql/json_test.rb b/activerecord/test/cases/adapters/postgresql/json_test.rb
index c74f70f251..273b2c1c7b 100644
--- a/activerecord/test/cases/adapters/postgresql/json_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/json_test.rb
@@ -113,6 +113,22 @@ module PostgresqlJSONSharedTestCases
     assert_equal(nil, x.payload)
   end
 
+  def test_select_nil_json_after_create
+    json = JsonDataType.create(payload: nil)
+    x = JsonDataType.where(payload:nil).first
+    assert_equal(json, x)
+  end
+
+  def test_select_nil_json_after_update
+    json = JsonDataType.create(payload: "foo")
+    x = JsonDataType.where(payload:nil).first
+    assert_equal(nil, x)
+
+    json.update_attributes payload: nil
+    x = JsonDataType.where(payload:nil).first
+    assert_equal(json.reload, x)
+  end
+
   def test_select_array_json_value
     @connection.execute %q|insert into json_data_type (payload) VALUES ('["v0",{"k1":"v1"}]')|
     x = JsonDataType.first
diff --git a/activerecord/test/cases/adapters/postgresql/transaction_test.rb b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
index d992e22305..c450524de8 100644
--- a/activerecord/test/cases/adapters/postgresql/transaction_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
@@ -1,5 +1,6 @@
 require "cases/helper"
 require "support/connection_helper"
+require "concurrent/atomic/cyclic_barrier"
 
 module ActiveRecord
   class PostgresqlTransactionTest < ActiveRecord::PostgreSQLTestCase
@@ -27,32 +28,29 @@ module ActiveRecord
     end
 
     test "raises SerializationFailure when a serialization failure occurs" do
-      with_warning_suppression do
-        assert_raises(ActiveRecord::SerializationFailure) do
-          thread = Thread.new do
-            Sample.transaction isolation: :serializable do
-              Sample.delete_all
+      assert_raises(ActiveRecord::SerializationFailure) do
+        before = Concurrent::CyclicBarrier.new(2)
+        after = Concurrent::CyclicBarrier.new(2)
 
-              10.times do |i|
-                sleep 0.1
-
-                Sample.create value: i
-              end
+        thread = Thread.new do
+          with_warning_suppression do
+            Sample.transaction isolation: :serializable do
+              before.wait
+              Sample.create value: Sample.sum(:value)
+              after.wait
             end
           end
+        end
 
-          sleep 0.1
-
-          Sample.transaction isolation: :serializable do
-            Sample.delete_all
-
-            10.times do |i|
-              sleep 0.1
-
-              Sample.create value: i
+        begin
+          with_warning_suppression do
+            Sample.transaction isolation: :serializable do
+              before.wait
+              Sample.create value: Sample.sum(:value)
+              after.wait
             end
           end
-
+        ensure
           thread.join
         end
       end
@@ -61,26 +59,28 @@ module ActiveRecord
     test "raises Deadlocked when a deadlock is encountered" do
       with_warning_suppression do
         assert_raises(ActiveRecord::Deadlocked) do
+          barrier = Concurrent::CyclicBarrier.new(2)
+
           s1 = Sample.create value: 1
           s2 = Sample.create value: 2
 
           thread = Thread.new do
             Sample.transaction do
               s1.lock!
-              sleep 1
+              barrier.wait
               s2.update_attributes value: 1
             end
           end
 
-          sleep 0.5
-
-          Sample.transaction do
-            s2.lock!
-            sleep 1
-            s1.update_attributes value: 2
+          begin
+            Sample.transaction do
+              s2.lock!
+              barrier.wait
+              s1.update_attributes value: 2
+            end
+          ensure
+            thread.join
           end
-
-          thread.join
         end
       end
     end
@@ -88,10 +88,11 @@ module ActiveRecord
     protected
 
       def with_warning_suppression
-        log_level = @connection.client_min_messages
-        @connection.client_min_messages = "error"
+        log_level = ActiveRecord::Base.connection.client_min_messages
+        ActiveRecord::Base.connection.client_min_messages = "error"
         yield
-        @connection.client_min_messages = log_level
+      ensure
+        ActiveRecord::Base.connection.client_min_messages = log_level
       end
   end
 end