Introduced concept of session. It does not yet support multiple databases, nor transactions, but it's a start!

lib/active_relation/relations.rb

@@ -11,4 +11,5 @@ require 'active_relation/relations/rename'
 require 'active_relation/relations/deletion'
 require 'active_relation/relations/insertion'
 require 'active_relation/relations/update'
-require 'active_relation/relations/alias'
+require 'active_relation/relations/alias'
+require 'active_relation/sessions/session'

lib/active_relation/relations/deletion.rb

@@ -10,6 +10,11 @@ module ActiveRelation
         "FROM #{table_sql}",
         ("WHERE #{selects.collect(&:to_sql).join('\n\tAND ')}" unless selects.blank?)
       ].compact.join("\n")
-    end  
+    end
+    
+    def ==(other)
+      self.class  == other.class    and
+      relation    == other.relation
+    end
   end
 end

lib/active_relation/relations/insertion.rb

@@ -11,13 +11,14 @@ module ActiveRelation
         "INSERT",
         "INTO #{table_sql}",
         "(#{record.keys.collect(&:to_sql).join(', ')})",
-        "VALUES #{inserts.collect(&:to_sql).join(', ')}"
+        "VALUES #{record.to_sql}"
       ].join("\n")
-    end  
-
-    protected
-    def inserts
-      relation.inserts + [record]
+    end
+    
+    def ==(other)
+      self.class  == other.class    and
+      relation    == other.relation and
+      record      == other.record
     end
   end
 end

lib/active_relation/relations/relation.rb

@@ -2,18 +2,22 @@ module ActiveRelation
   class Relation
     include Sql::Quoting
 
-    module Iteration
-      include Enumerable
-  
+    def session
+      Session.instance
+    end
+
+    module Enumerable
+      include ::Enumerable
+
       def each(&block)
-        connection.select_all(to_s).each(&block)
+        session.read(self).each(&block)
       end
-  
+
       def first
-        connection.select_one(to_s)
+        session.read(self).first
       end
     end
-    include Iteration
+    include Enumerable
 
     module Operations
       def join(other)
@@ -58,18 +62,25 @@ module ActiveRelation
       def rename(attribute, aliaz)
         Rename.new(self, attribute => aliaz)
       end
-  
-      def insert(record)
-        Insertion.new(self, record)
-      end
-  
-      def delete
-        Deletion.new(self)
-      end
-      
+        
       def aggregate(*expressions)
         AggregateOperation.new(self, expressions)
       end
+      
+      module Writes
+        def insert(record)
+          session.create Insertion.new(self, record); self
+        end
+
+        def update(assignments)
+          session.update Update.new(self, assignments); self
+        end
+
+        def delete
+          session.delete Deletion.new(self); self
+        end
+      end
+      include Writes
   
       JoinOperation = Struct.new(:join_sql, :relation1, :relation2) do
         def on(*predicates)
@@ -84,7 +95,7 @@ module ActiveRelation
       end
     end
     include Operations
-
+    
     def aggregation?
       false
     end

lib/active_relation/relations/update.rb

@@ -12,6 +12,12 @@ module ActiveRelation
         assignments.inject([]) { |assignments, (attribute, value)| assignments << "#{attribute.to_sql} = #{value.to_sql}" }.join(" "),
         ("WHERE #{selects.collect(&:to_sql).join('\n\tAND ')}" unless selects.blank?)
       ].join("\n")
-    end  
+    end
+    
+    def ==(other)
+      self.class  == other.class    and
+      relation    == other.relation and
+      assignments == other.assignments
+    end
   end
 end

lib/active_relation/sessions/session.rb

@@ -0,0 +1,38 @@
+require 'singleton'
+
+module ActiveRelation
+  class Session
+    include Singleton
+        
+    module CRUD
+      def connection
+        ActiveRecord::Base.connection
+      end
+      
+      def create(insert)
+        connection.insert(insert.to_sql)
+      end
+      
+      def read(select)
+        connection.select_all(select.to_sql)
+      end
+      
+      def update(update)
+        connection.update(update.to_sql)
+      end
+      
+      def delete(delete)
+        connection.delete(delete.to_sql)
+      end
+    end
+    include CRUD
+    
+    module Transactions
+    end
+    include Transactions
+    
+    module UnitOfWork
+    end
+    include UnitOfWork
+  end
+end

lib/active_relation/sql.rb

@@ -2,7 +2,7 @@ module ActiveRelation
   module Sql
     module Quoting
       def connection
-        ActiveRecord::Base.connection
+        Session.instance.connection
       end
   
       delegate :quote_table_name, :quote_column_name, :quote, :to => :connection

spec/active_relation/integration/scratch_spec.rb

@@ -136,24 +136,6 @@ describe 'ActiveRelation', 'A proposed refactoring to ActiveRecord, introducing
       """)
     end
 
-    describe 'write operations' do
-      it 'generates the query for user.destroy' do
-        @user.delete.to_sql.should be_like("""
-          DELETE
-          FROM `users`
-          WHERE `users`.`id` = 1
-        """)
-      end
-      
-     it 'generates an efficient query for two User.creates -- UnitOfWork is within reach!' do
-        @users.insert(@users[:name] => "humpty").insert(@users[:name] => "dumpty").to_sql.should be_like("""
-          INSERT
-          INTO `users`
-          (`users`.`name`) VALUES ('humpty'), ('dumpty')
-        """)
-      end
-    end
-
     describe 'with_scope' do
       it 'obviates the need for with_scope merging logic since, e.g.,
             `with_scope :conditions => ...` is just a #select operation on the relation' do

spec/active_relation/unit/relations/insertion_spec.rb

@@ -14,15 +14,6 @@ module ActiveRelation
           (`users`.`name`) VALUES ('nick')
         """)
       end
-    
-      it 'manufactures sql inserting the data for multiple items' do
-        nested_insertion = Insertion.new(@relation, @relation[:name] => "cobra")
-        Insertion.new(nested_insertion, nested_insertion[:name] => "commander").to_sql.should be_like("""
-          INSERT
-          INTO `users`
-          (`users`.`name`) VALUES ('cobra'), ('commander')
-        """)
-      end
     end
   end
 end

spec/active_relation/unit/relations/relation_spec.rb

@@ -36,13 +36,13 @@ module ActiveRelation
       end
     end
     
-    describe '#Expression?' do
+    describe '#aggregation?' do
       it "returns false" do
         @relation.should_not be_aggregation
       end
     end
 
-    describe 'read operations' do
+    describe Relation::Operations do
       describe 'joins' do
         before do
           @predicate = @relation[:id].equals(@relation[:id])
@@ -105,19 +105,34 @@ module ActiveRelation
             should == Aggregation.new(@relation, :expressions => [@expresion, @expression2], :groupings => [@attribute1, @attribute2])
         end
       end
-    end
-  
-    describe 'write operations' do
-      describe '#delete' do
-        it 'manufactures a deletion relation' do
-          @relation.delete.should be_kind_of(Deletion)
+      
+      describe Relation::Operations::Writes do
+        describe '#delete' do
+          it 'manufactures a deletion relation' do
+            mock(Session.instance).delete(Deletion.new(@relation))
+            @relation.delete.should == @relation
+          end
+        end
+
+        describe '#insert' do
+          it 'manufactures an insertion relation' do
+            mock(Session.instance).create(Insertion.new(@relation, record = {@relation[:name] => 'carl'}))
+            @relation.insert(record).should == @relation
+          end
+        end
+
+        describe '#update' do
+          it 'manufactures an update relation' do
+            mock(Session.instance).update(Update.new(@relation, assignments = {@relation[:name] => 'bob'}))
+            @relation.update(assignments).should == @relation
+          end
         end
       end
-    
-      describe '#insert' do
-        it 'manufactures an insertion relation' do
-          @relation.insert(record = {:id => 1}).should be_kind_of(Insertion)
-        end
+    end
+      
+    describe Relation::Enumerable do
+      it "is enumerable" do
+        pending
       end
     end
   end

spec/active_relation/unit/relations/update_spec.rb

@@ -21,7 +21,6 @@ module ActiveRelation
           WHERE `users`.`id` = 1
         """)
       end
-      
     end
   end
 end

spec/active_relation/unit/session/session_spec.rb

@@ -0,0 +1,70 @@
+require File.join(File.dirname(__FILE__), '..', '..', '..', 'spec_helper')
+
+module ActiveRelation
+  describe Session do
+    before do
+      @relation = Table.new(:users)
+      @session = Session.instance
+    end
+    
+    describe Singleton do
+      it "is a singleton" do
+        Session.instance.should be_equal(Session.instance)
+        lambda { Session.new }.should raise_error
+      end
+    end
+    
+    describe Session::CRUD do
+      before do
+        @insert = Insertion.new(@relation, @relation[:name] => 'nick')
+        @update = Update.new(@relation, @relation[:name] => 'nick')
+        @delete = Deletion.new(@relation)
+        @select = @relation
+      end
+      
+      describe '#create' do
+        it "should execute an insertion on the connection" do
+          mock(@session.connection).insert(@insert.to_sql)
+          @session.create(@insert)
+        end
+      end
+      
+      describe '#read' do
+        it "should execute an selection on the connection" do
+          mock(@session.connection).select_all(@select.to_sql)
+          @session.read(@select)
+        end
+      end
+      
+      describe '#update' do
+        it "should execute an update on the connection" do
+          mock(@session.connection).update(@update.to_sql)
+          @session.update(@update)
+        end
+      end
+      
+      describe '#delete' do
+        it "should execute a delete on the connection" do
+          mock(@session.connection).delete(@delete.to_sql)
+          @session.delete(@delete)
+        end
+      end
+    end
+    
+    describe Session::Transactions do
+      describe '#begin' do
+      end
+    
+      describe '#end' do
+      end
+    end
+    
+    describe Session::UnitOfWork do
+      describe '#flush' do
+      end
+      
+      describe '#clear' do
+      end
+    end
+  end
+end

spec/spec_helper.rb

@@ -7,7 +7,7 @@ Dir["#{dir}/matchers/*"].each { |m| require "#{dir}/matchers/#{File.basename(m)}
 require 'active_relation'
 
 ActiveRecord::Base.configurations = {
-  'sql_algebra_test' => {
+  'test' => {
     :adapter  => 'mysql',
     :username => 'root',
     :password => 'password',
@@ -15,7 +15,7 @@ ActiveRecord::Base.configurations = {
     :database => 'sql_algebra_test',
   },
 }
-ActiveRecord::Base.establish_connection 'sql_algebra_test'
+ActiveRecord::Base.establish_connection 'test'
 
 class Hash
   def shift