[AUTOTAG-24] Efficiency of regular expression under AbstractModelBody.evaluateAsString

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 1.2.0
• Labels: regex
• Assignee: Unassigned
• Reporter: Hubert Law
• Created: 17/Jan/18 02:50
• Updated: 17/Jan/18 02:59

Description

Despite AUTOTAG-21 the regex still eats up CPU time due to the inefficiency of the pattern s*$ which, in case of long consecutive white-space in the middle of the body, consumes O(n^2^) time while failing to match (since it will attempt to start matching at each white space position).

Matching the actual non-whitespace content directly may be more efficient in this case, e.g

private static final Pattern PATTERN = Pattern.compile("^\\s*+(\\S(?:.*\\S)?)\\s*$");

if (body != null) {
     final Matcher matcher = PATTERN.matcher(body);
     if (matcher.matches()) {
         body = matcher.group(1);
     } else {
         body = null;
     }  
 }

Backtracking is limited to the final white spaces, in linear time.