Clean up load_history in terms of list all unique participants for a session

ruby/lib/jam_ruby/models/music_session.rb

@@ -568,10 +568,22 @@ module JamRuby
       return query
     end
 
+    # list all unique participants in a session, for any session that the current_user was once a part of
     def self.history(current_user, options)
       offset = options[:offset] || 0
       limit = options[:limit] || 10
 
+      #This results in
+      #  SELECT  DISTINCT ON(music_sessions.created_at, music_sessions.id, users.id ) music_sessions.id AS session_id, music_sessions_user_history.id AS session_history_id, music_sessions.created_at, music_sessions.name, music_sessions.description, music_sessions.musician_access, music_sessions.approval_required, music_sessions_user_history.instruments, users.first_name, users.last_name, users.photo_url, users.id AS user_id FROM "music_sessions" INNER JOIN
+      #             music_sessions_user_history
+      #           ON
+      #             music_sessions.id = music_sessions_user_history.music_session_id
+      #           INNER JOIN
+      #             users
+      #           ON
+      #             music_sessions_user_history.user_id = users.id
+      #           WHERE music_sessions.id IN ( SELECT DISTINCT music_sessions_user_history.music_session_id FROM music_sessions_user_history where user_id = '1886af5c-b76e-466b-b8d1-30d98e549521)  ORDER BY music_sessions.created_at DESC LIMIT 100 OFFSET 1
+      #
       MusicSession.joins(
         %Q{
           INNER JOIN
@@ -582,9 +594,10 @@ module JamRuby
             users
           ON
             music_sessions_user_history.user_id = users.id
-          WHERE users.id = '#{current_user.id}'
+          WHERE music_sessions.id IN ( SELECT DISTINCT music_sessions_user_history.music_session_id FROM music_sessions_user_history where user_id = '#{current_user.id}')
+
         }
-      ).order('music_sessions.created_at DESC').select("music_sessions.id AS session_id, music_sessions_user_history.id AS session_history_id, music_sessions.created_at, music_sessions.name, music_sessions.description, music_sessions.musician_access, music_sessions.approval_required, music_sessions_user_history.instruments, users.first_name, users.last_name, users.photo_url, users.id AS user_id").offset(offset).limit(limit)
+      ).order('music_sessions.created_at DESC').select("DISTINCT ON(music_sessions.created_at, music_sessions.id, users.id ) music_sessions.id AS session_id, music_sessions_user_history.id AS session_history_id, music_sessions.created_at, music_sessions.name, music_sessions.description, music_sessions.musician_access, music_sessions.approval_required, music_sessions_user_history.instruments, users.first_name, users.last_name, users.photo_url, users.id AS user_id").offset(offset).limit(limit)
     end
 
     def self.scheduled user, only_public = false