[TxMt] TM freezes completely on search&replace in 6K-lines XML-File!

[John Johnson]

Sounds like a classic case of the regexp engine doing backtracking.

The regexp engine searches forward until it matches the regexp. Then it 
begins searching backward from the end of the file, until the regexp 
matches as much as possible. Which in this case is only one character. 
This is called greedy matching.

So the first thing you can do is make the match lazy. Tell the regexp 
engine it's okay to do as little as possible. You do that by adding a ? 
after the repeat modifier.

\n+?

That says match 1 or more newlines, but don't knock yourself out.

The second thing you can do is make the regexp so the engine doesn't 
have to search backward.

\n[^\n]

So that says "match a newline followed by something that isn't a 
newline." When the regexp engine sees that it has matched the whole 
pattern to begin with, it stops. In experiments I just did, this was 
the fastest, even faster that the lazy modifier.

If you have blank lines in your file (\n followed by \n), you can use 
this regexp:
\n+[^\n]

"Match one or more newlines, followed by a non-newline."

So it seems TextMate's regexp is working as it should.

Regards,
   JJ

On 16-Jan-2006, at 18:51, Tom Lazar wrote:

> whoha!
>
> I just wanted to do some xml-wrangling with TM and opened my usual 
> accounting file which contains ca. 6000 lines of xml.
>
> I work with it all the time and never experienced any problems. except 
> for right now, when i did a search and replace with regular 
> expressions, just simply remoing all line-breaks, ie. replacing '\n' 
> with nothing.
>
> TM has been maxing out the CPU for ten minutes now (Dual 1GHz G4) and 
> doesn't let me do anything. I've got ca 15 projects open and am 
> praying that they're saved.
>
> How can this be avoided in the future? is TM really only usable for 
> small files such as XHTML templates or code? that'd be a real shame...
>
> can anybody shed any light on this or give some advice, what other 
> product to use for the 'heavy lifting stuff'?
>
> best regards,
>
> tom
>
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