private String globToRegex(char glob) {
        switch (glob) {
        case'*':
            return ".*";
        case'?':
            return ".";
        case'^':
        case'$':
        case'|':
        case'{':
        case'}':
        case'(':
        case')':
        case'[':
        case']':
        case'\\':
        case'+':
        case'.':
            return "\\" + glob;
        default:
            return "" + glob;
        }
    }
Converts a single character in a glob expression to the corresponding regular expression string.

@param glob The glob character.
@return The regex string.
document/src/main/java/com/yahoo/document/select/rule/ComparisonNode.java