Remove CachedConnectionPerThread per-thread pooling mechanism in favor of a fixed pool with default maximum of 5 connections

activerecord/test/cases/locking_test.rb

@@ -280,6 +280,7 @@ unless current_adapter?(:SQLServerAdapter, :SybaseAdapter, :OpenBaseAdapter)
               sleep zzz       # block thread 2 for zzz seconds
             end
             t1 = Time.now
+            Person.clear_active_connections!
           end
 
           b = Thread.new do
@@ -287,6 +288,7 @@ unless current_adapter?(:SQLServerAdapter, :SybaseAdapter, :OpenBaseAdapter)
             t2 = Time.now
             Person.transaction { yield }
             t3 = Time.now
+            Person.clear_active_connections!
           end
 
           a.join

activerecord/test/cases/threaded_connections_test.rb

@@ -16,12 +16,14 @@ unless %w(FrontBase).include? ActiveRecord::Base.connection.adapter_name
 
   class PooledConnectionsTest < ActiveRecord::TestCase
     def setup
+      super
       @connection = ActiveRecord::Base.remove_connection
     end
 
     def teardown
       ActiveRecord::Base.clear_all_connections!
       ActiveRecord::Base.establish_connection(@connection)
+      super
     end
 
     def checkout_connections

activerecord/test/cases/transactions_test.rb

@@ -296,6 +296,7 @@ if current_adapter?(:PostgreSQLAdapter)
               topic.approved = !topic.approved?
               topic.save!
             end
+            Topic.clear_active_connections!
           end
         end
 
@@ -331,6 +332,7 @@ if current_adapter?(:PostgreSQLAdapter)
               dev = Developer.find(1)
               assert_equal original_salary, dev.salary
             end
+            Developer.clear_active_connections!
           end
         end
 
@@ -342,6 +344,7 @@ if current_adapter?(:PostgreSQLAdapter)
               # Always expect original salary.
               assert_equal original_salary, Developer.find(1).salary
             end
+            Developer.clear_active_connections!
           end
         end