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[PATCH 3/3] commit-graph: respect 'core.useBloomFilters'

From
Taylor Blau <me@ttaylorr.com>
Date
Jun 30, 2020, 17:17 UTC
Message-ID
<4cfa086e503e19763a9d581fcb6a2ef818776dfc.1593536481.git.me@ttaylorr.com>
In-Reply-To
<cover.1593536481.git.me@ttaylorr.com>

Git uses the 'core.commitGraph' configuration value to control whether or not the commit graph is used when parsing commits or performing a traversal.

Now that commit-graphs can also contain a section for changed-path Bloom filters, administrators that already have commit-graphs may find it convenient to use those graphs without relying on their changed-path Bloom filters. This can happen, for example, during a staged roll-out, or in the event of an incident.

Introduce 'core.useBloomFilters' to control whether or not Bloom filters are read. Note that this configuration is independent from both:

  - 'core.commitGraph', to allow flexibility in using all parts of a
    commit-graph _except_ for its Bloom filters.
  - The '--changed-paths' option for 'git commit-graph write', to allow
    reading and writing Bloom filters to be controlled independently.

When the variable is set, pretend as if no Bloom data was specified at all. This avoids adding additional special-casing outside of the commit-graph internals.

Suggested-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 Documentation/config/core.txt | 5 +++++
 commit-graph.c                | 4 ++--
 repo-settings.c               | 3 +++
 repository.h                  | 1 +
 t/helper/test-read-graph.c    | 3 ++-
 t/t4216-log-bloom.sh          | 4 +++-
 6 files changed, 16 insertions(+), 4 deletions(-)
diff --git a/Documentation/config/core.txt b/Documentation/config/core.txt
index 74619a9c03..b146bf8d34 100644
--- a/Documentation/config/core.txt
+++ b/Documentation/config/core.txt
@@ -599,6 +599,11 @@ core.commitGraph::
 	to parse the graph structure of commits. Defaults to true. See
 	linkgit:git-commit-graph[1] for more information.
 
+core.useBloomFilters::
+	If true, then git will use the changed-path Bloom filters in the
+	commit-graph file (if it exists, and they are present). Defaults to
+	true. See linkgit:git-commit-graph[1] for more information.
+
 core.useReplaceRefs::
 	If set to `false`, behave as if the `--no-replace-objects`
 	option was given on the command line. See linkgit:git[1] and
diff --git a/commit-graph.c b/commit-graph.c
index fdfb0888f0..03c00415c4 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -337,14 +337,14 @@ struct commit_graph *parse_commit_graph(struct repository *r,
 		case GRAPH_CHUNKID_BLOOMINDEXES:
 			if (graph->chunk_bloom_indexes)
 				chunk_repeated = 1;
-			else
+			else if (r->settings.core_use_bloom_filters)
 				graph->chunk_bloom_indexes = data + chunk_offset;
 			break;
 
 		case GRAPH_CHUNKID_BLOOMDATA:
 			if (graph->chunk_bloom_data)
 				chunk_repeated = 1;
-			else {
+			else if (r->settings.core_use_bloom_filters) {
 				uint32_t hash_version;
 				graph->chunk_bloom_data = data + chunk_offset;
 				hash_version = get_be32(data + chunk_offset);
diff --git a/repo-settings.c b/repo-settings.c
index dc6817daa9..d8e3b1c61e 100644
--- a/repo-settings.c
+++ b/repo-settings.c
@@ -17,9 +17,12 @@ void prepare_repo_settings(struct repository *r)
 
 	if (!repo_config_get_bool(r, "core.commitgraph", &value))
 		r->settings.core_commit_graph = value;
+	if (!repo_config_get_bool(r, "core.usebloomfilters", &value))
+		r->settings.core_use_bloom_filters = value;
 	if (!repo_config_get_bool(r, "gc.writecommitgraph", &value))
 		r->settings.gc_write_commit_graph = value;
 	UPDATE_DEFAULT_BOOL(r->settings.core_commit_graph, 1);
+	UPDATE_DEFAULT_BOOL(r->settings.core_use_bloom_filters, 1);
 	UPDATE_DEFAULT_BOOL(r->settings.gc_write_commit_graph, 1);
 
 	if (!repo_config_get_int(r, "index.version", &value))
diff --git a/repository.h b/repository.h
index 3c1f7d54bd..cc61533122 100644
--- a/repository.h
+++ b/repository.h
@@ -29,6 +29,7 @@ struct repo_settings {
 	int initialized;
 
 	int core_commit_graph;
+	int core_use_bloom_filters;
 	int gc_write_commit_graph;
 	int fetch_write_commit_graph;
 
diff --git a/t/helper/test-read-graph.c b/t/helper/test-read-graph.c
index 6d0c962438..5f585a1725 100644
--- a/t/helper/test-read-graph.c
+++ b/t/helper/test-read-graph.c
@@ -12,11 +12,12 @@ int cmd__read_graph(int argc, const char **argv)
 	setup_git_directory();
 	odb = the_repository->objects->odb;
 
+	prepare_repo_settings(the_repository);
+
 	graph = read_commit_graph_one(the_repository, odb);
 	if (!graph)
 		return 1;
 
-
 	printf("header: %08x %d %d %d %d\n",
 		ntohl(*(uint32_t*)graph->data),
 		*(unsigned char*)(graph->data + 4),
diff --git a/t/t4216-log-bloom.sh b/t/t4216-log-bloom.sh
index 0b4cc4f8d1..b1a247477e 100755
--- a/t/t4216-log-bloom.sh
+++ b/t/t4216-log-bloom.sh
@@ -90,7 +90,9 @@ do
 		      "--ancestry-path side..master"
 	do
 		test_expect_success "git log option: $option for path: $path" '
-			test_bloom_filters_used "$option -- $path"
+			test_bloom_filters_used "$option -- $path" &&
+			test_config core.useBloomFilters false &&
+			test_bloom_filters_not_used "$option -- $path"
 		'
 	done
 done
-- 
2.27.0.224.g4cfa086e50
Previous: Jeff KingNext: Jeff King
Message 12 of 16 in “commit-graph: introduce 'core.useBloomFilters'”
  1. 0/3 commit-graph: introduce 'core.useBloomFilters'Taylor Blau, Jun 30, 2020
  2. 1/3 commit-graph: pass a 'struct repository *' in more placesTaylor Blau, Jun 30, 2020
  3. Derrick StoleeJun 30, 2020
  4. 2/3 t4216: fix broken '&&'-chainTaylor Blau, Jun 30, 2020
  5. Eric SunshineJun 30, 2020
  6. Taylor BlauJun 30, 2020
  7. Jeff KingJun 30, 2020
  8. Taylor BlauJun 30, 2020
  9. Jeff KingJun 30, 2020
  10. Eric SunshineJun 30, 2020
  11. Jeff KingJun 30, 2020
  12. 3/3 commit-graph: respect 'core.useBloomFilters'Taylor Blau, Jun 30, 2020
  13. Jeff KingJun 30, 2020
  14. Taylor BlauJun 30, 2020
  15. Jeff KingJun 30, 2020
  16. Taylor BlauAug 3, 2020

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