Re: [PATCH 6/6] odb: introduce generic object counting

> Similar to the preceding commit, introduce counting of objects on the
> object database level, replacing the logic that we have in
> `repo_approximate_object_count()`.
>
> Note that the function knows to cache the object count. It's unclear
> whether this cache is really required as we shouldn't have that many
> cases where we count objects repeatedly. But to be on the safe side the
> caching mechanism is retained, with the only excepting being that we
> also have to use the passed flags as caching key.
>
> Signed-off-by: Patrick Steinhardt <ps@pks.im>
> ---
>  builtin/gc.c   |  6 +++++-
>  commit-graph.c |  3 ++-
>  object-name.c  |  6 +++++-
>  odb.c          | 37 ++++++++++++++++++++++++++++++++++++-
>  odb.h          | 17 +++++++++++++++--
>  packfile.c     | 27 ---------------------------
>  packfile.h     |  6 ------
>  7 files changed, 63 insertions(+), 39 deletions(-)
>
> diff --git a/builtin/gc.c b/builtin/gc.c
> index 3a64d28da8..cb9ca89a97 100644
> --- a/builtin/gc.c
> +++ b/builtin/gc.c
> @@ -574,9 +574,13 @@ static uint64_t total_ram(void)
>  static uint64_t estimate_repack_memory(struct gc_config *cfg,
>  				       struct packed_git *pack)
>  {
> -	unsigned long nr_objects = repo_approximate_object_count(the_repository);
> +	unsigned long nr_objects;
>  	size_t os_cache, heap;
>  
> +	if (odb_count_objects(the_repository->objects,
> +			      ODB_COUNT_OBJECTS_APPROXIMATE, &nr_objects) < 0)
> +		return 0;
> +
>  	if (!pack || !nr_objects)
>  		return 0;
>  
> diff --git a/commit-graph.c b/commit-graph.c
> index f8e24145a5..c030003330 100644
> --- a/commit-graph.c
> +++ b/commit-graph.c
> @@ -2607,7 +2607,8 @@ int write_commit_graph(struct odb_source *source,
>  			replace = ctx.opts->split_flags & COMMIT_GRAPH_SPLIT_REPLACE;
>  	}
>  
> -	ctx.approx_nr_objects = repo_approximate_object_count(r);
> +	if (odb_count_objects(r->objects, ODB_COUNT_OBJECTS_APPROXIMATE, &ctx.approx_nr_objects) < 0)
> +		ctx.approx_nr_objects = 0;
>  
>  	if (ctx.append && g) {
>  		for (i = 0; i < g->num_commits; i++) {
> diff --git a/object-name.c b/object-name.c
> index 7b14c3bf9b..e5adec4c9d 100644
> --- a/object-name.c
> +++ b/object-name.c
> @@ -837,7 +837,11 @@ int repo_find_unique_abbrev_r(struct repository *r, char *hex,
>  	const unsigned hexsz = algo->hexsz;
>  
>  	if (len < 0) {
> -		unsigned long count = repo_approximate_object_count(r);
> +		unsigned long count;
> +
> +		if (odb_count_objects(r->objects, ODB_COUNT_OBJECTS_APPROXIMATE, &count) < 0)
> +			count = 0;
> +
>  		/*
>  		 * Add one because the MSB only tells us the highest bit set,
>  		 * not including the value of all the _other_ bits (so "15"
> diff --git a/odb.c b/odb.c
> index 84a31084d3..350e23f3c0 100644
> --- a/odb.c
> +++ b/odb.c
> @@ -917,6 +917,41 @@ int odb_for_each_object(struct object_database *odb,
>  	return 0;
>  }
>  
> +int odb_count_objects(struct object_database *odb,
> +		      enum odb_count_objects_flags flags,
> +		      unsigned long *out)
> +{
> +	struct odb_source *source;
> +	unsigned long count = 0;
> +	int ret;
> +
> +	if (odb->object_count_valid && odb->object_count_flags == flags) {
> +		*out = odb->object_count;
> +		return 0;
> +	}
> +
> +	odb_prepare_alternates(odb);
> +	for (source = odb->sources; source; source = source->next) {
> +		unsigned long c;
> +
> +		ret = odb_source_count_objects(source, flags, &c);
> +		if (ret < 0)
> +			goto out;
> +
> +		count += c;
> +	}
> +
> +	odb->object_count = count;
> +	odb->object_count_valid = 1;
> +	odb->object_count_flags = flags;
> +
> +	*out = count;
> +	ret = 0;
> +
> +out:
> +	return ret;
> +}
> +
>  void odb_assert_oid_type(struct object_database *odb,
>  			 const struct object_id *oid, enum object_type expect)
>  {
> @@ -1030,7 +1065,7 @@ void odb_reprepare(struct object_database *o)
>  	for (source = o->sources; source; source = source->next)
>  		odb_source_reprepare(source);
>  
> -	o->approximate_object_count_valid = 0;
> +	o->object_count_valid = 0;
>  
>  	obj_read_unlock();
>  }
> diff --git a/odb.h b/odb.h
> index e6057477f6..7b004f1cf4 100644
> --- a/odb.h
> +++ b/odb.h
> @@ -112,8 +112,9 @@ struct object_database {
>  	 * These two fields are not meant for direct access. Use
>  	 * repo_approximate_object_count() instead.