function testIndexJoin_EmptyTable() {
  var tableARelation = lf.proc.Relation.fromRows([], [ta.getName()]);
  var tableBRelation = lf.proc.Relation.fromRows(tableBRows, [tb.getName()]);
  return checkIndexJoin(tableARelation, tableBRelation, tb['id'].eq(ta['id']));
}
Tests index join for the case where an empty relation is joined with the
entire TableB (using TableB's index for the join).
@return {!IThenable}