Meteor.publish('myClassScores', function(classId) {
  if(typeof classId !== 'number')
    throw new Error('classId must be integer');
  // Triggers require caches of columns that are joined on
  var assignmentIds = [], studentIds = [];
  // Prepare supporting query to main query
  var classAssignments = liveDb.select(`
      SELECT
        id
      FROM
        assignments
      WHERE
        class_id = ${liveDb.db.escape(classId)}
    `, [ {
      table: 'assignments',
      condition: function(row, newRow){
        return row.class_id === classId ||
          (newRow && newRow.class_id === classId);
      }
    } ]
  );
  // Update cache on new data
  classAssignments.on('update', function(diff, results) {
    assignmentIds = results.map(function(row) { return row.id });
  });
  // Subscription has been stopped, also stop supporting query
  this.onStop(function() {
    classAssignments.stop();
  });
  var classScores = liveDb.select(`
    SELECT
      students.name AS student_name,
      students.id AS student_id,
      assignments.name,
      assignments.value,
      scores.score
    FROM
      scores
    INNER JOIN assignments ON
      (assignments.id = scores.assignment_id)
    INNER JOIN students ON
      (students.id = scores.student_id)
    WHERE
      assignments.class_id = ${liveDb.db.escape(classId)};
  `, [
    {
      table: 'assignments',
      condition: function(row, newRow) {
        // newRow only passed on UPDATE events
        return row.class_id === classId ||
          (newRow && newRow.class_id === classId)
      }
    },
    {
      table: 'students',
      condition: function(row, newRow) {
        // Check if the id of this row matches cache value set
        return studentIds.indexOf(row.id) !== -1 ||
          (newRow && studentIds.indexOf(newRow.id) !== -1)
      }
    },
    {
      table: 'scores',
      condition: function(row, newRow) {
        // Check if the assignment_id of this row matches cache value set
        return assignmentIds.indexOf(row.assignment_id) !== -1 ||
          (newRow && assignmentIds.indexOf(newRow.assignment_id) !== -1)
      }
    }
  ]);
  classScores.on('update', function(diff, results) {
    // Update student_id cache
    studentIds = results.map(function(row) { return row.student_id });
  });
  return classScores;
});