Re: [jgit-dev] RevWalk.next() visits all commits on the first call when

[Tomasz Zarna <tzarna@xxxxxxxxx>]

Hi Mingyu,

> I will often break the loop in the middle after a couple of commits

Not sure which JGit version are you using, but in case it's not the
latest one: is the condition you meet something that can be set using
LogCommand#setMaxCount, #setSkip or alike? If not, is it something
that can be achieved in native git [1], but the API is missing in
JGit?

Cheers,
Tomek

[1] https://www.kernel.org/pub/software/scm/git/docs/git-log.html#_commit_limiting

On Thu, Jun 27, 2013 at 12:48 AM, Mingyu Kim <mkim@xxxxxxxxxxxx> wrote:
> I was using LogCommand to get the commit history for a particular file.
> Here's a code snippet.
>
> Iterable<RevCommit> iterable =
> git.log().add(startCommit).addPath(path).call(); // this is actually a
> RevWalk
> Iterator<RevCommit> iterator = iterable.iterator();
> While (iterator.hasNext()) {
> RevCommit next = iterator.next();
> // do something
> // break if certain condition is met
> }
>
> I noticed that the second line that initializes the iterator takes a long
> time and the running time grows linearly with the number of commits. After
> some more investigation, I noticed the entire log was computed at the second
> line, rather than being computed on demand when I call next(). The second
> line calls RevWalk.next(), which then calls StartGenerator.next(), and
> StartGenerator.next() creates FIFORevQueue if the tree filter is not ALL.
> (It's not ALL in my case because I added a path filter.) At construction,
> FIFORevQueue keeps calling Generator.next() until it returns null, which I
> believe visits all commits in the repository from the start point to the
> very initial commit.
>
> Basically, I'd like to be able to run the code snippet above and to pay the
> cost only for what's actually needed to fetch just the next commit because I
> will often break the loop in the middle after a couple of commits. Is there
> a way to avoid computing the entire log at the beginning and to do
> computation on-demans as I iterate through the commits? Is there any plan to
> fix this in the short term? I know I can simply iterate through the commits
> with a ALL tree filter and perform path filtering myself, but I'm wondering
> if there is a way to do this in a more native way in jgit.
>
> Thanks,
> Mingyu
>
>
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