add submission_ids to existing RFCs via SQL query (query included as a comment)

db/migrate/20160630154310_add_submission_to_request_for_comments.rb

@@ -3,3 +3,31 @@ class AddSubmissionToRequestForComments < ActiveRecord::Migration
     add_reference :request_for_comments, :submission
   end
 end
+
+=begin
+We issued the following on the database to add the submission_ids for existing entries
+
+UPDATE request_for_comments
+SET submission_id = sub.submission_id_external
+FROM
+(SELECT s.id AS submission_id_external,
+                rfc.id AS rfc_id,
+                          s.created_at AS submission_created_at,
+                                          rfc.created_at AS rfc_created_at
+FROM submissions s,
+                 request_for_comments rfc
+WHERE s.user_id = rfc.user_id
+AND s.exercise_id = rfc.exercise_id
+AND rfc.created_at + interval '2 hours' > s.created_at
+AND s.created_at =
+        (SELECT MAX(created_at)
+        FROM submissions
+        WHERE exercise_id = s.exercise_id
+        AND user_id = s.user_id
+        AND rfc.created_at + interval '2 hours' > created_at
+        GROUP BY s.exercise_id,
+                 s.user_id)) as sub
+WHERE id = sub.rfc_id
+AND submission_id IS NULL;
+
+=end