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Re: [RFC PATCH] Not computing changed path filter for root commits

From
Taylor Blau <me@ttaylorr.com>
Date
Oct 10, 2023, 19:47 UTC
Message-ID
<ZSWqStEpsFU0SmEm@nand.local>
In-Reply-To
<20231009205925.1915096-1-jonathantanmy@google.com>
On Mon, Oct 09, 2023 at 01:59:25PM -0700, Jonathan Tan wrote:
Show 27 quoted lines
> Taylor Blau <me@ttaylorr.com> writes:
> > This only happens when we return REV_TREE_NEW from a call to
> > `rev_compare_tree(revs, p, commit, nth_parent)`. But we'll only get
> > REV_TREE_NEW back if
> >
> >     repo_get_commit_tree(the_repository, p);
> >
> > returns NULL. But when we call rev_same_tree_as_empty(revs, p) in the
> > REV_TREE_NEW case, we return early as follows:
> >
> >     struct tree *t1 = repo_get_commit_tree(revs, p);
> >     if (!t1)
> >       return 0;
> >
> > So we won't even consult the Bloom filter in that case, since t1 is NULL
> > for the same reason as what caused rev_compare_tree() to return
> > REV_TREE_NEW in the first place.
> >
> > I am still dumbfounded by how we would ever get REV_TREE_NEW in the
> > first place, but if we did, I think we would be OK here.
> >
> > Thanks,
> > Taylor
>
> Ah, good point. Your patch in
> https://lore.kernel.org/git/ZQnmTXUO94%2FQy8mq@nand.local/ looks good to
> me, then.

Oops, I made a mistake in the quoted portion, which is that we could get REV_TREE_NEW if the tree-diff itself only adds files. This is the non-trivial case that we get when t1 is non-NULL, and we end up calling `diff_tree_oid()` which sets the static `tree_difference` variable.

So I think adding an nth_parent field (like you originally suggested[^1]) makes sense.

Thanks, Taylor

[^1]: Thanks for being patient with me ;-).
Previous: Jonathan TanNext: Taylor Blau
Message 9 of 10 in “Not computing changed path filter for root commits”
  1. Not computing changed path filter for root commitsJonathan Tan, Sep 11, 2023
  2. Junio C HamanoSep 15, 2023
  3. SZEDER GáborSep 15, 2023
  4. Taylor BlauSep 19, 2023
  5. Jonathan TanOct 2, 2023
  6. Taylor BlauOct 9, 2023
  7. Taylor BlauOct 9, 2023
  8. Jonathan TanOct 9, 2023
  9. Taylor BlauOct 10, 2023
  10. Taylor BlauSep 19, 2023

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