func (f *Format) mustNotBe(f2 Format) { *f &^= f2 }

var formatNames = map[Format]string{
	formatV7: "V7", FormatUSTAR: "USTAR", FormatPAX: "PAX", FormatGNU: "GNU", formatSTAR: "STAR",
}

func (f Format) String() string {
	var ss []string
	for f2 := Format(1); f2 < formatMax; f2 <<= 1 {
		if f.has(f2) {
			ss = append(ss, formatNames[f2])
		}
	}
	switch len(ss) {
	case 0:
		return "<unknown>"

	return ns.formatName("fk", rel.Schema.Table, ns.toDBName(rel.Name))
}

// CheckerName generate checker name
func (ns NamingStrategy) CheckerName(table, column string) string {
	return ns.formatName("chk", table, column)
}

// IndexName generate index name
func (ns NamingStrategy) IndexName(table, column string) string {
	return ns.formatName("idx", table, ns.toDBName(column))
}