[bug #24903] grep multiple items is really slow

[Kremer David Jean-Pierre]

URL:
  <http://savannah.gnu.org/bugs/?24903>

                 Summary: grep multiple items is really slow
                 Project: grep
            Submitted by: dkremer_me
            Submitted on: sam 22 nov 2008 19:31:12 GMT
                Category: None
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

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Details:

Hello. I have noticed that performing a search with multiple items
(expression made of OR logical operators) is very slow.

grep '\(something\|another\|else\|what\|you\|want\)' my_large_file is really,
really, and incredibly slow.

When a normal pattern research takes 40 minutes on my file, this takes more
than four hours (and more).

So, I think it's a big performance problem, and should be resolved, but I
don't know exactly why this happens. I will take a look in the source code
maybe.


See you later.




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