Merge branch 'appearance-creation-transaction'

CHANGELOG.md

@@ -1,3 +1,4 @@
+ * Create transaction and lock when creating a new appearance.
  * Remove votes from vote CSV file that have NA for Appearance ID.
  * Alter response for all_object_info_totals_by_date to be valid XML.
 

app/models/question.rb

@@ -186,28 +186,31 @@ def get_optional_information(params)
       if params[:with_appearance] && visitor_identifier.present?
         visitor = current_user.visitors.find_or_create_by_identifier(visitor_identifier)
 
-        last_appearance = get_first_unanswered_appearance(visitor)
-
-        if last_appearance.nil?
-          @prompt = choose_prompt(:algorithm => params[:algorithm])
-          @appearance = current_user.record_appearance(visitor, @prompt)
-        else
-        #only display a new prompt and new appearance if the old prompt has not been voted on
-          @appearance = last_appearance
-          @prompt= @appearance.prompt
+        Appearance.transaction do
+          last_appearance = get_first_unanswered_appearance(visitor)
+          if last_appearance.nil?
+            @prompt = choose_prompt(:algorithm => params[:algorithm])
+            @appearance = current_user.record_appearance(visitor, @prompt)
+          else
+            #only display a new prompt and new appearance if the old prompt has not been voted on
+            @appearance = last_appearance
+            @prompt= @appearance.prompt
+          end
         end
 
         if params[:future_prompts]
           num_future = params[:future_prompts][:number].to_i rescue 1
           num_future.times do |number|
             offset = number + 1
-            last_appearance = get_first_unanswered_appearance(visitor, offset)
-            if last_appearance.nil?
-              @future_prompt = choose_prompt(:algorithm => params[:algorithm])
-              @future_appearance = current_user.record_appearance(visitor, @future_prompt)
-            else
-              @future_appearance = last_appearance
-              @future_prompt= @future_appearance.prompt
+            Appearance.transaction do
+              last_appearance = get_first_unanswered_appearance(visitor, offset)
+              if last_appearance.nil?
+                @future_prompt = choose_prompt(:algorithm => params[:algorithm])
+                @future_appearance = current_user.record_appearance(visitor, @future_prompt)
+              else
+                @future_appearance = last_appearance
+                @future_prompt= @future_appearance.prompt
+              end
             end
 
             result.merge!({"future_appearance_id_#{offset}".to_sym => @future_appearance.lookup})
@@ -675,21 +678,28 @@ def export(type, options = {})
     return csv_data
   end
 
+  # Gets the user n'th unanswered appearance where n is the value of offset.
+  #
+  # Lock is set to true for the SELECT query because this method is called
+  # inside a transaction that will add a row matching these parameters if one
+  # doesn't already exist.
   def get_first_unanswered_appearance(visitor, offset=0)
-       last_appearance = visitor.appearances.find(:first, 
-              :conditions => {:question_id => self.id,
-                        :answerable_id => nil
-                                   },
-              :order => 'id ASC',
-              :offset => offset)
-       if last_appearance && !last_appearance.prompt.active?
+    unanswered_appearances = visitor.appearances.find(:all,
+      :conditions => {
+        :question_id => self.id,
+        :answerable_id => nil
+      },
+      :order => 'id ASC',
+      :lock => true
+    )
+    last_appearance = unanswered_appearances[offset]
+    if last_appearance && !last_appearance.prompt.active?
       last_appearance.valid_record = false
       last_appearance.validity_information = "Deactivated Prompt"
       last_appearance.save
-
       return get_first_unanswered_appearance(visitor)
-       end
-       last_appearance
+    end
+    last_appearance
   end
 
   def votes_per_uploaded_choice(only_active=false)