[
  {
    "destination" : "incline_timeline",
    "source"      : [ "incline_tweet", "incline_follow" ],
    "pk_columns"  : {
      "incline_follow.follower" : "user_id",
      "incline_tweet.id"        : "tweet_id"
    },
    "merge"       : {
      "incline_tweet.user_id" : "incline_follow.followee"
    },
    "shard-key"   : "user_id"
  }
]