fixing issue where if the index contained a nil, queries would fail

lib/dynamoid/criteria/chain.rb

@@ -97,16 +97,8 @@ def records
       #
       # @since 0.2.0
       def records_with_index
-        ids = if index.range_key?
-          Dynamoid::Adapter.query(index.table_name, index_query).collect{|r| r[:ids]}.inject(Set.new) {|set, result| set + result}
-        else
-          results = Dynamoid::Adapter.read(index.table_name, index_query[:hash_value], consistent_opts)
-          if results
-            results[:ids]
-          else
-            []
-          end
-        end
+        ids = ids_from_index
+
         if ids.nil? || ids.empty?
           []
         else
@@ -121,6 +113,20 @@ def records_with_index
         end
       end
 
+      # Returns the Set of IDs from the index table.
+      #
+      # @return [Set] a Set containing the IDs from the index.
+      def ids_from_index
+        if index.range_key?
+          Dynamoid::Adapter.query(index.table_name, index_query).inject(Set.new) do |all, record|
+            all + Set.new(record[:ids])
+          end
+        else
+          results = Dynamoid::Adapter.read(index.table_name, index_query[:hash_value], consistent_opts)
+          results ? results[:ids] : []
+        end
+      end
+
       def records_with_range
         Dynamoid::Adapter.query(source.table_name, range_query).collect {|hash| source.new(hash).tap { |r| r.new_record = false } }
       end

spec/dynamoid/criteria/chain_spec.rb

@@ -73,6 +73,14 @@
     @chain.send(:records_without_index).should == [@user]
   end
 
+  it "doesn't crash if it finds a nil id in the index" do
+    @chain.query = {:name => 'Josh', "created_at.gt" => @time - 1.day}
+    Dynamoid::Adapter.expects(:query).
+                      with("dynamoid_tests_index_user_created_ats_and_names", kind_of(Hash)).
+                      returns([{ids: nil}, {ids: Set.new([42])}])
+    @chain.send(:ids_from_index).should == Set.new([42])
+  end
+
   it 'defines each' do
     @chain.query = {:name => 'Josh'}
     @chain.each {|u| u.update_attribute(:name, 'Justin')}