Conditional insert if the previous json data was different

json_insert.pl

  return !!$self->query(<<'  SQL', $id, {json => $data})->rows;
    INSERT INTO server_data (server_id, data)
    SELECT $1, $2
    WHERE COALESCE((
      SELECT data <> $2 
      FROM server_data
      WHERE server_id=$1
      ORDER BY ts DESC
      LIMIT 1
    ), 't')
  SQL