create a real table alias

lib/arel/table.rb

@@ -6,7 +6,7 @@ class Table
     @engine = nil
     class << self; attr_accessor :engine; end
 
-    attr_accessor :name, :engine, :aliases, :table_alias
+    attr_accessor :name, :engine, :aliases, :table_alias, :options
 
     # TableAlias and Table both have a #table_name which is the name of the underlying table
     alias :table_name :name
@@ -18,6 +18,7 @@ def initialize name, engine = Table.engine
       @aliases = []
       @table_alias = nil
       @primary_key = nil
+      @options = (Hash === engine) ? engine : {}
 
       if Hash === engine
         @engine  = engine[:engine] || Table.engine
@@ -48,6 +49,10 @@ def alias name = "#{self.name}_2"
       end
     end
 
+    def as table_alias
+      Table.new(name, options.merge(:as => table_alias))
+    end
+
     def from table
       SelectManager.new(@engine, table)
     end

test/test_table.rb

@@ -103,6 +103,23 @@ module Arel
       end
     end
 
+    describe 'as' do
+      it 'should create a node that is like the original table' do
+        @relation.must_respond_to(:as)
+
+        node = @relation.as(:foo)
+        node.must_be_kind_of(Table)
+        node.name.must_equal 'users'
+        node.table_alias.to_sym.to_s.must_equal 'foo'
+
+        node.wont_equal @relation
+
+        # this tries to compare the columns by name in order to verify that the tables are the same
+        col_name = lambda { |col| col.name }
+        node.columns.map(&col_name).must_equal @relation.columns.map(&col_name)
+      end
+    end
+
     describe 'new' do
       it 'should accept an engine' do
         rel = Table.new :users, 'foo'