lib/arel/engines/sql/relations/table.rb in arel-0.2.1 vs lib/arel/engines/sql/relations/table.rb in arel-0.3.0

@@ -1,10 +1,10 @@
 module Arel
   class Table < Relation
     include Recursion::BaseCase
 
-    cattr_accessor :engine
+    cattr_accessor :engine, :tables
     attr_reader :name, :engine, :table_alias, :options
 
     def initialize(name, options = {})
       @name = name.to_s
 
@@ -13,18 +13,38 @@
         @engine = options[:engine] || Table.engine
         @table_alias = options[:as].to_s if options[:as].present? && options[:as].to_s != @name
       else
         @engine = options # Table.new('foo', engine)
       end
+
+      if @engine.connection
+        begin
+          require "arel/engines/sql/compilers/#{@engine.adapter_name.downcase}_compiler"
+          @@tables ||= engine.tables
+        rescue LoadError
+          raise "#{@engine.adapter_name} is not supported by Arel."
+        end
+      end
     end
 
     def as(table_alias)
       Table.new(name, options.merge(:as => table_alias))
     end
 
+    def table_exists?
+      if @table_exists
+        true
+      else
+        @table_exists = @@tables.include?(name) || engine.table_exists?(name)
+      end
+    end
+
     def attributes
-      @attributes ||= columns.collect do |column|
-        Attribute.new(self, column.name.to_sym)
+      return @attributes if defined?(@attributes)
+      if table_exists?
+        @attributes = columns.collect { |column| Attribute.new(self, column.name.to_sym) }
+      else
+        []
       end
     end
 
     def eql?(other)
       self == other