[v5,2/9] commit-graph: don't call write_graph_chunk_large_edges() unnecessarily

Commit Message

Ævar Arnfjörð Bjarmason Jan. 16, 2019, 1:29 p.m. UTC

From: SZEDER Gábor <[e-mail]>

The optional 'Large Edge List' chunk of the commit graph file stores
parent information for commits with more than two parents.  Since the
chunk is optional, write_commit_graph() looks through all commits to
find those with more than two parents, and then writes the commit
graph file header accordingly, i.e. if there are no such commits, then
there won't be a 'Large Edge List' chunk written, only the three
mandatory chunks.

However, when it comes to writing chunk data, write_commit_graph()
unconditionally invokes write_graph_chunk_large_edges(), even when it
was decided earlier that that chunk won't be written.  Strictly
speaking there is no bug here, because write_graph_chunk_large_edges()
won't write anything because it won't find any commits with more than
two parents, but then it unnecessarily and in vain looks through all
commits once again in search for such commits.

Don't call write_graph_chunk_large_edges() when that chunk won't be
written to spare an unnecessary iteration over all commits.

Signed-off-by: SZEDER Gábor <[e-mail]>
Signed-off-by: Ævar Arnfjörð Bjarmason <[e-mail]>
---
 commit-graph.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Patch

diff --git a/commit-graph.c b/commit-graph.c
index ab292e5d01..38b62051c2 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -944,7 +944,8 @@  void write_commit_graph(const char *obj_dir,
 	write_graph_chunk_fanout(f, commits.list, commits.nr);
 	write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr);
 	write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr);
-	write_graph_chunk_large_edges(f, commits.list, commits.nr);
+	if (num_large_edges)
+		write_graph_chunk_large_edges(f, commits.list, commits.nr);
 
 	close_commit_graph(the_repository);
 	finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);