Open in Compare Editor (aka diff) -- incredibly slow!

[x77686d]

I've got a 947-line MXML file that seems to require over a minute of CPU time to "Open in Compare Editor".

Specifically, I'm using Flex Builder 3 as an Eclipse 3.3.2 plug-in with Subclipse 1.2.4. If I synchronize with repository that runs in a few seconds. If I then try to view the diff for the file in question (main.mxml), the CPU goes to 100% and eclipse.exe piles up about 1:19 of CPU time.

I tried a few experiments with chopping out parts of the file. Here are times to Open in Compare Editor single-line diffs with only the first N lines of the file in question:

400 lines: 56 seconds
200 lines: 15 seconds
150 lines: 4 seconds
100 lines: instantaneous

Executive summary: OUCH!

[dr_zeus]

I've heard that XML is hard to diff. Combine that with the fact that you have nearly 1000 lines of it, and I'm not surprised.

[jsebrech]

I would suggest feeding it through another compare tool. Not being able to diff a 1000 line file (in any format) in less than a minute is ridiculous.