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>

Taylor Blau committed Jul 1, 2020 at 13:27 UTC f3c2a36810d5322747ad573f7e2b8404d4f67ead

2 files changed +8

revision.c

@@ -702,6 +702,10 @@ static void prepare_to_use_bloom_filter(struct rev_info *revs)

702 path = pi->match;

703

704 len = strlen(path);

705 + if (!len) {

706 + revs->bloom_filter_settings = NULL;

707 + return;

708 + }

709

710 revs->bloom_key = xmalloc(sizeof(struct bloom_key));

711 fill_bloom_key(path, len, revs->bloom_key, revs->bloom_filter_settings);

t/t4216-log-bloom.sh

@@ -112,6 +112,10 @@ test_expect_success 'git log -- multiple path specs does not use Bloom filters'

112 test_bloom_filters_not_used "-- file4 A/file1"

113 '

114

115 +test_expect_success 'git log -- "." pathspec at root does not use Bloom filters' '

116 + test_bloom_filters_not_used "-- ."

117 +'

118 +

119 test_expect_success 'git log with wildcard that resolves to a single path uses Bloom filters' '

120 test_bloom_filters_used "-- *4" &&

121 test_bloom_filters_used "-- *renamed"