In 1efd88283ef68d912df215125951a87526768a51, ConnectionAdapters was put under eager_autoload. Due to the requires in that file, this caused ConnectionSpecification to be loaded, which references ActiveRecord::Base, which means the database connection is established. We do not want to connect to the database when Active Record is loaded, only when ActiveRecord::Base is first referenced by the user.

1 files changed, 22 insertions, 12 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 077cf7df1b..60e2f811a2 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -4,20 +4,30 @@ require 'bigdecimal/util'
 require 'active_support/core_ext/benchmark'
 require 'active_support/deprecation'
 
-# TODO: Autoload these files
-require 'active_record/connection_adapters/column'
-require 'active_record/connection_adapters/abstract/schema_definitions'
-require 'active_record/connection_adapters/abstract/schema_statements'
-require 'active_record/connection_adapters/abstract/database_statements'
-require 'active_record/connection_adapters/abstract/quoting'
-require 'active_record/connection_adapters/abstract/connection_pool'
-require 'active_record/connection_adapters/abstract/connection_specification'
-require 'active_record/connection_adapters/abstract/query_cache'
-require 'active_record/connection_adapters/abstract/database_limits'
-require 'active_record/result'
-
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
+    extend ActiveSupport::Autoload
+
+    autoload :Column
+
+    autoload_under 'abstract' do
+      autoload :IndexDefinition,  'active_record/connection_adapters/abstract/schema_definitions'
+      autoload :ColumnDefinition, 'active_record/connection_adapters/abstract/schema_definitions'
+      autoload :TableDefinition,  'active_record/connection_adapters/abstract/schema_definitions'
+
+      autoload :SchemaStatements
+      autoload :DatabaseStatements
+      autoload :DatabaseLimits
+      autoload :Quoting
+
+      autoload :ConnectionPool
+      autoload :ConnectionHandler,       'active_record/connection_adapters/abstract/connection_pool'
+      autoload :ConnectionManagement,    'active_record/connection_adapters/abstract/connection_pool'
+      autoload :ConnectionSpecification
+
+      autoload :QueryCache
+    end
+
     # Active Record supports multiple database systems. AbstractAdapter and
     # related classes form the abstraction layer which makes this possible.
     # An AbstractAdapter represents a connection to a database, and provides an