Code review comment for lp:~ian-clatworthy/bzr/faster-dirstate-saving

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Ian Clatworthy wrote:
>> Brief thought: perhaps simply don't bother updating the dirstate file if the
>> number of changes is very small? (Or do we already do this?)
>
> Poolie has agreed with this so I'll go ahead and resubmit accordingly. The updated benchmark time for 'bzr status file' on OOo is 0.5 seconds, down from 1.0 second.
>
> We just need to agree on a # of changes below which it's not worth saving. I suggest we should save for 3 or more changes - so we skip iff 2 or less files are changed. If someone has a better number, let me know.

A guideline is: "Don't save if it would cost as much data as you avoid
reading".

The cost of not updating the dirstate is having to re-read the file
who's sha is now different. So if the dirstate is 1MB, and the file is
10k, then you should not update if there are 10 files that are changed.

If you *want* to look at text_size and compare it to len(lines) we could
do that. Otherwise I'm fine with a heuristic of < 1% of the tree, or
something like that.

John
=:->
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