revision: empty pathspecs should not use Bloom filters

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 <me@ttaylorr.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/revision.c b/revision.c
index ddf09ab0aa94b9643de04735c0a75e03fad35392..667ca36e1cc7f093a5684c465147b2d366e8acb4 100644 (file)
--- 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 52ad998f9e09b05f23eeee26eb9ca918ee1ad2cb..29338f36bf4c1c8e3d3d76fca60f9515c9e334d6 100755 (executable)
--- 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"