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PORegex performance issues with possible back tracking?
 

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  1. PORegex performance issues with possible back tracking?
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    <p>I have the following input/output and regex code that works fine (for the below input/output).</p> <p>-- input --</p> <pre><code>keep this keep this too Bye ------ Remove Below ------ remove all of this </code></pre> <p>-- output --</p> <pre><code>keep this keep this too Bye </code></pre> <p>-- code -- </p> <pre><code> String text = "keep this\n \n" + " keep this too\n \n Bye\n------ Remove Below ------\n remove all of this\n"; System.out.println(text); Pattern PATTERN = Pattern.compile("^(.*?)(-+)(.*?)Remove Below(.*?)(-+)(.*?)$", Pattern.DOTALL); Matcher m = PATTERN.matcher(text); if (m.find()) { // remove everything as expected (from about input-&gt;regex-&gt;output) text = ((m.group(1)).replaceAll("[\n]+$", "")).replaceAll("\\s+$", ""); System.out.println(m.group(1)); System.out.println(text); } </code></pre> <p>Ok, so this works great. However, this is for a test with the defined input output. When I get large files that I have to parse that contain the following sequence of characters/patterns I'm seeing the code take a while to execute (4-5sec) per the Find() method on files that are say 100k in size that have the following pattern. In fact sometimes I'm not sure if it's returning or not...when I step though as a debug test the find() method hangs and my client disconnects.</p> <p>NOTE: There is nothing to match in this file...but this is a pattern that is taxing my regex.</p> <p>-- 100k file -- </p> <pre><code>junk here more junk here o o o (even more junk per the ellipses) -------------------------------------this is junk junk here more junk here o o o (even more junk per the ellipses) -------------------------------------this is junk junk here more junk here o o o (even more junk per the ellipses) -------------------------------------this is junk junk here more junk here o o o (even more junk per the ellipses) this repeats from above to make up the 100k file. </code></pre> <p>-- ASK --</p> <blockquote> <p>How can I optimize the above regex to handle large file patterns from above as such or is this normal for regex parse speed (4-6sec) let along hanging altogether?</p> </blockquote>
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