[v4,09/10] revision: empty pathspecs should not use Bloom filters

Commit Message

John Cai via GitGitGadget July 1, 2020, 1:27 p.m. UTC

From: Taylor Blau <[e-mail]>

The prepare_to_use_bloom_filter() method was not intended to be called
on an empty pathspec. However, 'git log -- .' and 'git log' are subtly
different: the latter reports all commits while the former will simplify
commits that do not change the root tree.

This means that the path used to construct the bloom_key might be empty,
and that value is not added to the Bloom filter during construction.
That means that the results are likely incorrect!

To resolve the issue, be careful about the length of the path and stop
filling Bloom filters. To be completely sure we do not use them, drop
the pointer to the bloom_filter_settings from the commit-graph. That
allows our test to look at the trace2 logs to verify no Bloom filter
statistics are reported.

Signed-off-by: Taylor Blau <[e-mail]>
Signed-off-by: Derrick Stolee <[e-mail]>
---
 revision.c           | 4 ++++
 t/t4216-log-bloom.sh | 4 ++++
 2 files changed, 8 insertions(+)

Patch

diff --git a/revision.c b/revision.c
index ddf09ab0aa..667ca36e1c 100644
--- a/revision.c
+++ b/revision.c
@@ -702,6 +702,10 @@  static void prepare_to_use_bloom_filter(struct rev_info *revs)
 		path = pi->match;
 
 	len = strlen(path);
+	if (!len) {
+		revs->bloom_filter_settings = NULL;
+		return;
+	}
 
 	revs->bloom_key = xmalloc(sizeof(struct bloom_key));
 	fill_bloom_key(path, len, revs->bloom_key, revs->bloom_filter_settings);
diff --git a/t/t4216-log-bloom.sh b/t/t4216-log-bloom.sh
index 52ad998f9e..29338f36bf 100755
--- a/t/t4216-log-bloom.sh
+++ b/t/t4216-log-bloom.sh
@@ -112,6 +112,10 @@  test_expect_success 'git log -- multiple path specs does not use Bloom filters'
 	test_bloom_filters_not_used "-- file4 A/file1"
 '
 
+test_expect_success 'git log -- "." pathspec at root does not use Bloom filters' '
+	test_bloom_filters_not_used "-- ."
+'
+
 test_expect_success 'git log with wildcard that resolves to a single path uses Bloom filters' '
 	test_bloom_filters_used "-- *4" &&
 	test_bloom_filters_used "-- *renamed"