1 files changed, 67 insertions, 36 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 4c3a8f7233..07c2bc44d9 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -3,29 +3,34 @@ require 'bigdecimal'
 require 'bigdecimal/util'
 require 'active_support/core_ext/benchmark'
 require 'active_support/deprecation'
+require 'active_record/connection_adapters/schema_cache'
+require 'monitor'
 
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
     extend ActiveSupport::Autoload
 
     autoload :Column
+    autoload :ConnectionSpecification
 
-    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 :Table,            'active_record/connection_adapters/abstract/schema_definitions'
+    autoload_at 'active_record/connection_adapters/abstract/schema_definitions' do
+      autoload :IndexDefinition
+      autoload :ColumnDefinition
+      autoload :TableDefinition
+      autoload :Table
+    end
+
+    autoload_at 'active_record/connection_adapters/abstract/connection_pool' do
+      autoload :ConnectionHandler
+      autoload :ConnectionManagement
+    end
 
+    autoload_under 'abstract' do
       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
 
@@ -47,39 +52,44 @@ module ActiveRecord
       include DatabaseLimits
       include QueryCache
       include ActiveSupport::Callbacks
+      include MonitorMixin
 
       define_callbacks :checkout, :checkin
 
-      attr_accessor :visitor
-
-      def initialize(connection, logger = nil) #:nodoc:
-        @active = nil
-        @connection, @logger = connection, logger
+      attr_accessor :visitor, :pool
+      attr_reader :schema_cache, :last_use, :in_use
+      alias :in_use? :in_use
+
+      def initialize(connection, logger = nil, pool = nil) #:nodoc:
+        super()
+
+        @active              = nil
+        @connection          = connection
+        @in_use              = false
+        @instrumenter        = ActiveSupport::Notifications.instrumenter
+        @last_use            = false
+        @logger              = logger
+        @open_transactions   = 0
+        @pool                = pool
+        @query_cache         = Hash.new { |h,sql| h[sql] = {} }
         @query_cache_enabled = false
-        @query_cache = Hash.new { |h,sql| h[sql] = {} }
-        @open_transactions = 0
-        @instrumenter = ActiveSupport::Notifications.instrumenter
-        @visitor = nil
-      end
-
-      # Returns a visitor instance for this adaptor, which conforms to the Arel::ToSql interface
-      def self.visitor_for(pool) # :nodoc:
-        adapter = pool.spec.config[:adapter]
-
-        if Arel::Visitors::VISITORS[adapter]
-          ActiveSupport::Deprecation.warn(
-            "Arel::Visitors::VISITORS is deprecated and will be removed. Database adapters " \
-            "should define a visitor_for method which returns the appropriate visitor for " \
-            "the database. For example, MysqlAdapter.visitor_for(pool) returns " \
-            "Arel::Visitors::MySQL.new(pool)."
-          )
-
-          Arel::Visitors::VISITORS[adapter].new(pool)
-        else
-          Arel::Visitors::ToSql.new(pool)
+        @schema_cache        = SchemaCache.new self
+        @visitor             = nil
+      end
+
+      def lease
+        synchronize do
+          unless in_use
+            @in_use   = true
+            @last_use = Time.now
+          end
         end
       end
 
+      def expire
+        @in_use = false
+      end
+
       # Returns the human-readable name of the adapter. Use mixed case - one
       # can always use downcase if needed.
       def adapter_name
@@ -130,6 +140,22 @@ module ActiveRecord
         false
       end
 
+      # Does this adapter support index sort order?
+      def supports_index_sort_order?
+        false
+      end
+
+      # Does this adapter support partial indices?
+      def supports_partial_index?
+        false
+      end
+
+      # Does this adapter support explain? As of this writing sqlite3,
+      # mysql2, and postgresql are the only ones that do.
+      def supports_explain?
+        false
+      end
+
       # QUOTING ==================================================
 
       # Override to return the quoted table name. Defaults to column quoting.
@@ -246,6 +272,11 @@ module ActiveRecord
         "active_record_#{open_transactions}"
       end
 
+      # Check the connection back in to the connection pool
+      def close
+        pool.checkin self
+      end
+
       protected
 
         def log(sql, name = "SQL", binds = [])