Function balancedTableRefs

backend/plugin/parser/tidb/backup.go:783–793

balancedTableRefs returns s (trimmed) with parentheses balanced. omni's JoinClause/TableRef Loc excludes a wrapping "(" or ")", so a sliced table-ref list can carry an unmatched ")" (a parenthesized left join operand) and/or an unmatched "(" (a right operand). The missing parentheses only group, so

(s string)

// unmatched "(" (a right operand). The missing parentheses only group, so their
// source position is irrelevant — prepend "(" and append ")" to balance.
func balancedTableRefs(s string) string {
	leading, trailing := parenDeficit(s)
	s = strings.TrimSpace(s)
	if leading > 0 {
		s = strings.Repeat("(", leading) + s
	}
	if trailing > 0 {
		s += strings.Repeat(")", trailing)
	}
	return s
}

// parenDeficit returns how many "(" must be prepended and ")" appended to
// balance s, ignoring parentheses inside string/identifier literals ('...',