class JoinToOneParent implements AISValidation {

    @Override
    public void validate(AkibanInformationSchema ais, AISValidationOutput output) {
        Set<Table> childTables = new HashSet<>();
        
        for (Join join : ais.getJoins().values()) {
            if (childTables.contains(join.getChild())) {
                output.reportFailure(new AISValidationFailure (
                        new JoinToMultipleParentsException (join.getChild().getName())));
            } else {
                childTables.add(join.getChild());
            }
        }
    }

}