diff mbox series

[3/8] commit-graph.c: peel refs in 'add_ref_to_set'

Message ID 5ff56feab55b005b4a4d9559909ce7a08e5fa81e.1588641176.git.me@ttaylorr.com (mailing list archive)
State New, archived
Headers show
Series commit-graph: drop CHECK_OIDS, peel in callers | expand

Commit Message

Taylor Blau May 5, 2020, 1:13 a.m. UTC
While iterating references (to discover the set of commits to write to
the commit-graph with 'git commit-graph write --reachable'),
'add_ref_to_set' can save 'fill_oids_from_commits()' some time by
peeling the references beforehand.

Move peeling out of 'fill_oids_from_commits()' and into
'add_ref_to_set()' to use 'peel_ref()' instead of 'deref_tag()'. Doing
so allows the commit-graph machinery to use the peeled value from
'$GIT_DIR/packed-refs' instead of having to load and parse tags.

While we're at it, discard non-commit objects reachable from ref tips.
This would be done automatically by 'fill_oids_from_commits()', but such
functionality will be removed in a subsequent patch after the call to
'lookup_commit_reference_gently' is dropped (at which point a non-commit
object in the commits oidset will become an error).

Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 commit-graph.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Comments

Jeff King May 7, 2020, 7:54 p.m. UTC | #1
On Mon, May 04, 2020 at 07:13:43PM -0600, Taylor Blau wrote:

> While iterating references (to discover the set of commits to write to
> the commit-graph with 'git commit-graph write --reachable'),
> 'add_ref_to_set' can save 'fill_oids_from_commits()' some time by
> peeling the references beforehand.
> 
> Move peeling out of 'fill_oids_from_commits()' and into
> 'add_ref_to_set()' to use 'peel_ref()' instead of 'deref_tag()'. Doing
> so allows the commit-graph machinery to use the peeled value from
> '$GIT_DIR/packed-refs' instead of having to load and parse tags.

Or having to load and parse commits only to find out that they're not
tags. :)

> diff --git a/commit-graph.c b/commit-graph.c
> index 8f61256b0a..5c3fad0dd7 100644
> --- a/commit-graph.c
> +++ b/commit-graph.c
> @@ -1327,11 +1327,15 @@ static int add_ref_to_set(const char *refname,
>  			  const struct object_id *oid,
>  			  int flags, void *cb_data)
>  {
> +	struct object_id peeled;
>  	struct refs_cb_data *data = (struct refs_cb_data *)cb_data;
>  
>  	display_progress(data->progress, oidset_size(data->commits) + 1);
>  
> -	oidset_insert(data->commits, oid);
> +	if (peel_ref(refname, &peeled))
> +		peeled = *oid;

It may be the old-timer C programmer in me, but I always look slightly
suspicious at struct assignments. We know that object_id doesn't need a
deep copy, so it's obviously OK here. But should we use oidcpy() as a
style thing?

Alternatively, you could do this without a struct copy at all with:

  if (!peel_ref(...))
         oid = peeled;
  oidset_insert(..., oid);

which is actually a bit cheaper.

> +	if (oid_object_info(the_repository, &peeled, NULL) == OBJ_COMMIT)
> +		oidset_insert(data->commits, &peeled);

I probably would have left adding this "if" until a later step, but I
think it's OK here.

-Peff
Taylor Blau May 13, 2020, 7:48 p.m. UTC | #2
On Thu, May 07, 2020 at 03:54:41PM -0400, Jeff King wrote:
> On Mon, May 04, 2020 at 07:13:43PM -0600, Taylor Blau wrote:
>
> > While iterating references (to discover the set of commits to write to
> > the commit-graph with 'git commit-graph write --reachable'),
> > 'add_ref_to_set' can save 'fill_oids_from_commits()' some time by
> > peeling the references beforehand.
> >
> > Move peeling out of 'fill_oids_from_commits()' and into
> > 'add_ref_to_set()' to use 'peel_ref()' instead of 'deref_tag()'. Doing
> > so allows the commit-graph machinery to use the peeled value from
> > '$GIT_DIR/packed-refs' instead of having to load and parse tags.
>
> Or having to load and parse commits only to find out that they're not
> tags. :)
>
> > diff --git a/commit-graph.c b/commit-graph.c
> > index 8f61256b0a..5c3fad0dd7 100644
> > --- a/commit-graph.c
> > +++ b/commit-graph.c
> > @@ -1327,11 +1327,15 @@ static int add_ref_to_set(const char *refname,
> >  			  const struct object_id *oid,
> >  			  int flags, void *cb_data)
> >  {
> > +	struct object_id peeled;
> >  	struct refs_cb_data *data = (struct refs_cb_data *)cb_data;
> >
> >  	display_progress(data->progress, oidset_size(data->commits) + 1);
> >
> > -	oidset_insert(data->commits, oid);
> > +	if (peel_ref(refname, &peeled))
> > +		peeled = *oid;
>
> It may be the old-timer C programmer in me, but I always look slightly
> suspicious at struct assignments. We know that object_id doesn't need a
> deep copy, so it's obviously OK here. But should we use oidcpy() as a
> style thing?
>
> Alternatively, you could do this without a struct copy at all with:
>
>   if (!peel_ref(...))
>          oid = peeled;
>   oidset_insert(..., oid);
>
> which is actually a bit cheaper.

Makes sense, I think this version is the better of the two that you
suggested here. I noticed one small thing which is that since peeled is
only on the stack, I think we actually want 'oid = &peeled', but
otherwise I took this as-is.

> > +	if (oid_object_info(the_repository, &peeled, NULL) == OBJ_COMMIT)
> > +		oidset_insert(data->commits, &peeled);
>
> I probably would have left adding this "if" until a later step, but I
> think it's OK here.

Yeah, I did it here to avoid having to add a seemingly-unrelated change
later on. I agree it doesn't matter much, so in the interest of leaving
the series alone, I'll leave it where it is here.

> -Peff

Thanks,
Taylor
Jeff King May 13, 2020, 8:17 p.m. UTC | #3
On Wed, May 13, 2020 at 01:48:48PM -0600, Taylor Blau wrote:

> > Alternatively, you could do this without a struct copy at all with:
> >
> >   if (!peel_ref(...))
> >          oid = peeled;
> >   oidset_insert(..., oid);
> >
> > which is actually a bit cheaper.
> 
> Makes sense, I think this version is the better of the two that you
> suggested here. I noticed one small thing which is that since peeled is
> only on the stack, I think we actually want 'oid = &peeled', but
> otherwise I took this as-is.

Yes, definitely. That's what I get for writing code in my email editor. :)

-Peff
diff mbox series

Patch

diff --git a/commit-graph.c b/commit-graph.c
index 8f61256b0a..5c3fad0dd7 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -1327,11 +1327,15 @@  static int add_ref_to_set(const char *refname,
 			  const struct object_id *oid,
 			  int flags, void *cb_data)
 {
+	struct object_id peeled;
 	struct refs_cb_data *data = (struct refs_cb_data *)cb_data;
 
 	display_progress(data->progress, oidset_size(data->commits) + 1);
 
-	oidset_insert(data->commits, oid);
+	if (peel_ref(refname, &peeled))
+		peeled = *oid;
+	if (oid_object_info(the_repository, &peeled, NULL) == OBJ_COMMIT)
+		oidset_insert(data->commits, &peeled);
 	return 0;
 }