Comment 24 for bug 374730

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Craig Hewetson wrote:
> The latest version has a slight decrease in performance (from 1 minute to 3
> minutes)
> I suppose its because it is working getting all the revisions this time.
>

So revno 4677 works by pulling out the subset of files underneath 'dir'
for each revision, and then comparing them to see if anything has
changed. This means that 'bzr log BIGDIR' is slower than 'bzr log
SMALLDIR'. (in testing bzrlib vs tools, it was 5m30s vs 36s, which is a
lot.)

I've got another branch going:
  lp:///~jameinel/bzr/2.0.1-faster-get-deltas-bug374730

Which changes things at a different level. So that instead of extracting
the subset of files, it computes the changes for each revision, and then
deltas those.

In the 'ideal' case, you would take the intersection of both, so while
you are culling wrt changes you also cull wrt the subset of files you
care about. I'm not 100% sure of the benefit, just because of the
specifics of the data storage.

At the moment, the new method is around 50s for tools (slower), but
bzrlib is 2m10s (faster).

We're still a ways off of 'ideal', but hopefully I'll be able to poke
around a bit more.

John
=:->
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