Should I create one complex RegEx or multiple and less complex ones?

Question

Should I create one complex RegEx to tackle all cases on hand or should I break one complex RegEx in multiple Regex which ?

I'm concerned regarding performance using complex Regex. Will breaking the complex Regex into smaller simple regex perform better?

Answer 1

If you want a meaningful answer to the performance question, you need to benchmark both cases.

Regarding readability/maintainability, you can write unreadable code in any language and so you can do with regular expressions. If you write a big one, be sure to use the x modifier (IgnorePatternWhitespace in c#) and use comments to build your regex.

A randomly chosen example from one of my past answers in c#:

MatchCollection result = Regex.Matches
    (testingString,
        @"       
            (?<=\$)  # Ensure there is a $ before the string
            [^|]*    # Match any character that is not a |
            (?=\|)   #Till a | is ahead
        "
        , RegexOptions.IgnorePatternWhitespace);

Answer 2

I don't think there would be much of a difference now because of compiler optimization, however, using a simple one would make understanding your code easier which in turn makes maintenance easier.