[PATCH] commit-graph: add verify changed paths option

[PATCH] commit-graph: add verify changed paths option

[Son Luong Ngoc via GitGitGadget]

From: Son Luong Ngoc <sluongng@gmail.com>

Add '--has-changed-paths' option to 'git commit-graph verify' subcommand
to validate whether the commit-graph was written with '--changed-paths'
option.

Signed-off-by: Son Luong Ngoc <sluongng@gmail.com>
---
    Commit-Graph: Verify bloom filter
    
    When I was working on git-care(1) and Gitaly(2), the need to check
    whether a commit-graph (split or non-split) were built with Bloom
    filter. This is needed especially when a repository primary commit-graph
    write strategy is '--split' and the bottom chains might rarely be
    re-written (or never) thus Bloom filter is never applied to the graph.
    
    Provides users with a straight forward way to validate the existence of
    Bloom filter chunks to save user having to read the commit-graph
    manually as show in (1) and (2).
    
    References:
    
     1. https://github.com/sluongng/git-care/commit/d0feaa381ea3ec7b0e617c6596ad6e3cf16b884a
     2. https://gitlab.com/sluongng/gitaly/-/commit/78dba8b73e720b11500482b19b755346ec853025
    
    
    ------------------------------------------------------------------------
    
    It's probably going to take me a bit more time to write up some tests
    for this, so I want to send it out first for comments.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-687%2Fsluongng%2Fsluongngoc%2Fverify-bloom-filter-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-687/sluongng/sluongngoc/verify-bloom-filter-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/687

 builtin/commit-graph.c | 12 +++++++++---
 commit-graph.c         | 22 +++++++++++++++++-----
 commit-graph.h         | 12 +++++++++---
 3 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/builtin/commit-graph.c b/builtin/commit-graph.c
index 16c9f6101a..ce8a7cbe90 100644
--- a/builtin/commit-graph.c
+++ b/builtin/commit-graph.c
@@ -18,7 +18,8 @@ static char const * const builtin_commit_graph_usage[] = {
 };
 
 static const char * const builtin_commit_graph_verify_usage[] = {
-	N_("git commit-graph verify [--object-dir <objdir>] [--shallow] [--[no-]progress]"),
+	N_("git commit-graph verify [--object-dir <objdir>] [--shallow] "
+	    "[--has-changed-paths] [--[no-]progress]"),
 	NULL
 };
 
@@ -37,6 +38,7 @@ static struct opts_commit_graph {
 	int append;
 	int split;
 	int shallow;
+	int has_changed_paths;
 	int progress;
 	int enable_changed_paths;
 } opts;
@@ -71,12 +73,14 @@ static int graph_verify(int argc, const char **argv)
 	int open_ok;
 	int fd;
 	struct stat st;
-	int flags = 0;
+	enum commit_graph_verify_flags flags = 0;
 
 	static struct option builtin_commit_graph_verify_options[] = {
 		OPT_STRING(0, "object-dir", &opts.obj_dir,
 			   N_("dir"),
 			   N_("The object directory to store the graph")),
+		OPT_BOOL(0, "has-changed-paths", &opts.has_changed_paths,
+			 N_("verify that the commit-graph includes changed paths")),
 		OPT_BOOL(0, "shallow", &opts.shallow,
 			 N_("if the commit-graph is split, only verify the tip file")),
 		OPT_BOOL(0, "progress", &opts.progress, N_("force progress reporting")),
@@ -94,8 +98,10 @@ static int graph_verify(int argc, const char **argv)
 		opts.obj_dir = get_object_directory();
 	if (opts.shallow)
 		flags |= COMMIT_GRAPH_VERIFY_SHALLOW;
+	if (opts.has_changed_paths)
+		flags |= COMMIT_GRAPH_VERIFY_CHANGED_PATHS;
 	if (opts.progress)
-		flags |= COMMIT_GRAPH_WRITE_PROGRESS;
+		flags |= COMMIT_GRAPH_VERIFY_PROGRESS;
 
 	odb = find_odb(the_repository, opts.obj_dir);
 	graph_name = get_commit_graph_filename(odb);
diff --git a/commit-graph.c b/commit-graph.c
index 1af68c297d..d83f5a2325 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -250,7 +250,7 @@ struct commit_graph *load_commit_graph_one_fd_st(int fd, struct stat *st,
 	return ret;
 }
 
-static int verify_commit_graph_lite(struct commit_graph *g)
+static int verify_commit_graph_lite(struct commit_graph *g, int verify_changed_path)
 {
 	/*
 	 * Basic validation shared between parse_commit_graph()
@@ -276,6 +276,16 @@ static int verify_commit_graph_lite(struct commit_graph *g)
 		error("commit-graph is missing the Commit Data chunk");
 		return 1;
 	}
+	if (verify_changed_path) {
+		if (!g->chunk_bloom_indexes) {
+			error("commit-graph is missing Bloom Index chunk");
+			return 1;
+		}
+		if (!g->chunk_bloom_data) {
+			error("commit-graph is missing Bloom Data chunk");
+			return 1;
+		}
+	}
 
 	return 0;
 }
@@ -439,7 +449,7 @@ struct commit_graph *parse_commit_graph(void *graph_map, size_t graph_size)
 
 	hashcpy(graph->oid.hash, graph->data + graph->data_len - graph->hash_len);
 
-	if (verify_commit_graph_lite(graph))
+	if (verify_commit_graph_lite(graph, 0))
 		goto free_and_return;
 
 	return graph;
@@ -2216,7 +2226,9 @@ static void graph_report(const char *fmt, ...)
 #define GENERATION_ZERO_EXISTS 1
 #define GENERATION_NUMBER_EXISTS 2
 
-int verify_commit_graph(struct repository *r, struct commit_graph *g, int flags)
+int verify_commit_graph(struct repository *r,
+			struct commit_graph *g,
+			enum commit_graph_verify_flags flags)
 {
 	uint32_t i, cur_fanout_pos = 0;
 	struct object_id prev_oid, cur_oid, checksum;
@@ -2231,7 +2243,7 @@ int verify_commit_graph(struct repository *r, struct commit_graph *g, int flags)
 		return 1;
 	}
 
-	verify_commit_graph_error = verify_commit_graph_lite(g);
+	verify_commit_graph_error = verify_commit_graph_lite(g, flags & COMMIT_GRAPH_VERIFY_CHANGED_PATHS);
 	if (verify_commit_graph_error)
 		return verify_commit_graph_error;
 
@@ -2284,7 +2296,7 @@ int verify_commit_graph(struct repository *r, struct commit_graph *g, int flags)
 	if (verify_commit_graph_error & ~VERIFY_COMMIT_GRAPH_ERROR_HASH)
 		return verify_commit_graph_error;
 
-	if (flags & COMMIT_GRAPH_WRITE_PROGRESS)
+	if (flags & COMMIT_GRAPH_VERIFY_PROGRESS)
 		progress = start_progress(_("Verifying commits in commit graph"),
 					g->num_commits);
 
diff --git a/commit-graph.h b/commit-graph.h
index 28f89cdf3e..29c01b5000 100644
--- a/commit-graph.h
+++ b/commit-graph.h
@@ -94,6 +94,12 @@ enum commit_graph_write_flags {
 	COMMIT_GRAPH_WRITE_BLOOM_FILTERS = (1 << 3),
 };
 
+enum commit_graph_verify_flags {
+	COMMIT_GRAPH_VERIFY_SHALLOW       = (1 << 0),
+	COMMIT_GRAPH_VERIFY_CHANGED_PATHS = (1 << 1),
+	COMMIT_GRAPH_VERIFY_PROGRESS      = (1 << 2),
+};
+
 enum commit_graph_split_flags {
 	COMMIT_GRAPH_SPLIT_UNSPECIFIED      = 0,
 	COMMIT_GRAPH_SPLIT_MERGE_PROHIBITED = 1,
@@ -122,9 +128,9 @@ int write_commit_graph(struct object_directory *odb,
 		       enum commit_graph_write_flags flags,
 		       const struct split_commit_graph_opts *split_opts);
 
-#define COMMIT_GRAPH_VERIFY_SHALLOW	(1 << 0)
-
-int verify_commit_graph(struct repository *r, struct commit_graph *g, int flags);
+int verify_commit_graph(struct repository *r,
+			struct commit_graph *g,
+			enum commit_graph_verify_flags flags);
 
 void close_commit_graph(struct raw_object_store *);
 void free_commit_graph(struct commit_graph *);

base-commit: 47ae905ffb98cc4d4fd90083da6bc8dab55d9ecc
-- 
gitgitgadget

Re: [PATCH] commit-graph: add verify changed paths option

[Christian Couder]

On Fri, Jul 31, 2020 at 9:52 AM Son Luong Ngoc via GitGitGadget
<gitgitgadget@gmail.com> wrote:
>
> From: Son Luong Ngoc <sluongng@gmail.com>
>
> Add '--has-changed-paths' option to 'git commit-graph verify' subcommand
> to validate whether the commit-graph was written with '--changed-paths'
> option.
>
> Signed-off-by: Son Luong Ngoc <sluongng@gmail.com>

[...]

>     It's probably going to take me a bit more time to write up some tests
>     for this,

It would need some documentation too.

> so I want to send it out first for comments.

[...]

> diff --git a/builtin/commit-graph.c b/builtin/commit-graph.c
> index 16c9f6101a..ce8a7cbe90 100644
> --- a/builtin/commit-graph.c
> +++ b/builtin/commit-graph.c
> @@ -18,7 +18,8 @@ static char const * const builtin_commit_graph_usage[] = {
>  };
>
>  static const char * const builtin_commit_graph_verify_usage[] = {
> -       N_("git commit-graph verify [--object-dir <objdir>] [--shallow] [--[no-]progress]"),
> +       N_("git commit-graph verify [--object-dir <objdir>] [--shallow] "
> +           "[--has-changed-paths] [--[no-]progress]"),
>         NULL
>  };
>
> @@ -37,6 +38,7 @@ static struct opts_commit_graph {
>         int append;
>         int split;
>         int shallow;
> +       int has_changed_paths;
>         int progress;
>         int enable_changed_paths;
>  } opts;
> @@ -71,12 +73,14 @@ static int graph_verify(int argc, const char **argv)
>         int open_ok;
>         int fd;
>         struct stat st;
> -       int flags = 0;
> +       enum commit_graph_verify_flags flags = 0;
>
>         static struct option builtin_commit_graph_verify_options[] = {
>                 OPT_STRING(0, "object-dir", &opts.obj_dir,
>                            N_("dir"),
>                            N_("The object directory to store the graph")),
> +               OPT_BOOL(0, "has-changed-paths", &opts.has_changed_paths,
> +                        N_("verify that the commit-graph includes changed paths")),
>                 OPT_BOOL(0, "shallow", &opts.shallow,
>                          N_("if the commit-graph is split, only verify the tip file")),
>                 OPT_BOOL(0, "progress", &opts.progress, N_("force progress reporting")),
> @@ -94,8 +98,10 @@ static int graph_verify(int argc, const char **argv)
>                 opts.obj_dir = get_object_directory();
>         if (opts.shallow)
>                 flags |= COMMIT_GRAPH_VERIFY_SHALLOW;
> +       if (opts.has_changed_paths)
> +               flags |= COMMIT_GRAPH_VERIFY_CHANGED_PATHS;

I wonder if OPT_BIT() could be used instead of OPT_BOOL() above to
directly set the above flag, as the 'has_changed_paths' field in
'struct opts_commit_graph' seems to be used only for the purpose of
setting this flag.

>         if (opts.progress)
> -               flags |= COMMIT_GRAPH_WRITE_PROGRESS;
> +               flags |= COMMIT_GRAPH_VERIFY_PROGRESS;

Does this change belong to this patch? I think it would deserve an
explanation in the commit message if that's the case.

>         odb = find_odb(the_repository, opts.obj_dir);
>         graph_name = get_commit_graph_filename(odb);
> diff --git a/commit-graph.c b/commit-graph.c
> index 1af68c297d..d83f5a2325 100644
> --- a/commit-graph.c
> +++ b/commit-graph.c
> @@ -250,7 +250,7 @@ struct commit_graph *load_commit_graph_one_fd_st(int fd, struct stat *st,
>         return ret;
>  }
>
> -static int verify_commit_graph_lite(struct commit_graph *g)
> +static int verify_commit_graph_lite(struct commit_graph *g, int verify_changed_path)

[...]

> -int verify_commit_graph(struct repository *r, struct commit_graph *g, int flags)
> +int verify_commit_graph(struct repository *r,
> +                       struct commit_graph *g,
> +                       enum commit_graph_verify_flags flags)

It seems to me that it would be more coherent to have both
verify_commit_graph() and verify_commit_graph_lite() accept an 'enum
commit_graph_verify_flags flags' argument.

Right now the "has_changed_paths" option is first an int, then it's
converted to a flag and then to an int again before being passed to
verify_commit_graph_lite(). It would be simpler if it could be a flag
all along.

Thanks,
Christian.

Re: [PATCH] commit-graph: add verify changed paths option

[Junio C Hamano]

"Son Luong Ngoc via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Son Luong Ngoc <sluongng@gmail.com>
>
> Add '--has-changed-paths' option to 'git commit-graph verify' subcommand
> to validate whether the commit-graph was written with '--changed-paths'
> option.

The implementation seems to be only about "does this section exist?"
and not "does this section have healthy/uncorrupted data?", which
feels a bit strange for "verify".  Instead of setting ourselves up
to having to add "--has-this-section" and "--has-that-section" every
time a new kind of data is added to the system, how about giving the
verify command an option to list all the sections found in the file,
or a separate "git commit-graph list-sections" subcommand?

Re: [PATCH] commit-graph: add verify changed paths option

[Jeff King]

On Fri, Jul 31, 2020 at 07:49:25AM +0000, Son Luong Ngoc via GitGitGadget wrote:

> From: Son Luong Ngoc <sluongng@gmail.com>
> 
> Add '--has-changed-paths' option to 'git commit-graph verify' subcommand
> to validate whether the commit-graph was written with '--changed-paths'
> option.

Is a single boolean flag sufficient? If you have incrementals, you might
have some slices with this chunk and some without. What should the
boolean be in that case?

I thought we had some way of reporting the number of commits covered by
filters, but I can't seem to find it.

Our "test-tool read-graph" can report on whether there's a bloom filter
chunk, but I think it also doesn't distinguish between different slices
(and anyway, it wouldn't be suitable for tools that don't rely on an
actual built git.git directory).

-Peff

Re: [PATCH] commit-graph: add verify changed paths option

[Taylor Blau]

On Fri, Jul 31, 2020 at 10:14:39AM -0700, Junio C Hamano wrote:
> "Son Luong Ngoc via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
> > From: Son Luong Ngoc <sluongng@gmail.com>
> >
> > Add '--has-changed-paths' option to 'git commit-graph verify' subcommand
> > to validate whether the commit-graph was written with '--changed-paths'
> > option.
>
> The implementation seems to be only about "does this section exist?"
> and not "does this section have healthy/uncorrupted data?", which
> feels a bit strange for "verify".  Instead of setting ourselves up
> to having to add "--has-this-section" and "--has-that-section" every
> time a new kind of data is added to the system, how about giving the
> verify command an option to list all the sections found in the file,
> or a separate "git commit-graph list-sections" subcommand?

Completely agreed. When I suggested that Son work on this, I more had in
mind something like 'git commit-graph verify --changed-paths' to mean
"verify the integrity of the commit-graph(s), including regenerating
changed-path Bloom filters and making sure they match".

If you are just curious whether or not the section exists, I'd rather
write a script to look for the 'BIDX' or 'BDAT' chunk IDs. That said, if
they're spread across incremental, maybe it makes more sense to extend
the commit-graph test tool.

I dunno.

Thanks,
Taylor

Re: [PATCH] commit-graph: add verify changed paths option

[Taylor Blau]

On Fri, Jul 31, 2020 at 02:02:35PM -0400, Jeff King wrote:
> On Fri, Jul 31, 2020 at 07:49:25AM +0000, Son Luong Ngoc via GitGitGadget wrote:
>
> > From: Son Luong Ngoc <sluongng@gmail.com>
> >
> > Add '--has-changed-paths' option to 'git commit-graph verify' subcommand
> > to validate whether the commit-graph was written with '--changed-paths'
> > option.
>
> Is a single boolean flag sufficient? If you have incrementals, you might
> have some slices with this chunk and some without. What should the
> boolean be in that case?

I think you'd really want to know which layers do and don't have
filters. It might be even more interesting to have a tool like what 'git
show-index' is to '*.idx' files, maybe something like 'git show-graph'
or 'git show-commit-graph'. Its output would be one line per commit that
shows:

  - what layer in the chain it's located at
  - its graph_pos
  - its generation number
  - whether or not it has a Bloom filter
  - ???

That would be a useful tool for debugging anyway, even outside of the
test suite. It would be even better if we could replace the test-tool
with it.

On an unrelated note; this patch is broken as-is, since it will only
report that Bloom filters exist if the top-most graph has them. I have a
patch to fix this that I have been meaning to send out for most of this
week. I'll try to get to it shortly.

> I thought we had some way of reporting the number of commits covered by
> filters, but I can't seem to find it.

I don't recall having anything like that.

> Our "test-tool read-graph" can report on whether there's a bloom filter
> chunk, but I think it also doesn't distinguish between different slices
> (and anyway, it wouldn't be suitable for tools that don't rely on an
> actual built git.git directory).
>
> -Peff
Thanks,
Taylor

Re: [PATCH] commit-graph: add verify changed paths option

[Jeff King]

On Fri, Jul 31, 2020 at 02:09:56PM -0400, Taylor Blau wrote:

> > Is a single boolean flag sufficient? If you have incrementals, you might
> > have some slices with this chunk and some without. What should the
> > boolean be in that case?
> 
> I think you'd really want to know which layers do and don't have
> filters. It might be even more interesting to have a tool like what 'git
> show-index' is to '*.idx' files, maybe something like 'git show-graph'
> or 'git show-commit-graph'. Its output would be one line per commit that
> shows:
> 
>   - what layer in the chain it's located at
>   - its graph_pos
>   - its generation number
>   - whether or not it has a Bloom filter
>   - ???
> 
> That would be a useful tool for debugging anyway, even outside of the
> test suite. It would be even better if we could replace the test-tool
> with it.

Yeah, that was exactly what I had in mind, except that I'd make it a
sub-command of "git commit-graph" ("show" or perhaps "dump").

-Peff

Re: [PATCH] commit-graph: add verify changed paths option

[Son Luong Ngoc]

Note: re-send  to mailing list due to me forgot to turn on Plain Text format.
(sorry for the noise)

Hi Peff, Taylor, Junio and Christian,

Thanks a lot for the valuable feedbacks.
This is exactly what I was hoping for by sending out the patch early!

> On Jul 31, 2020, at 21:14, Jeff King <peff@peff.net> wrote:
> 
> On Fri, Jul 31, 2020 at 02:09:56PM -0400, Taylor Blau wrote:
> 
>>> Is a single boolean flag sufficient? If you have incrementals, you might
>>> have some slices with this chunk and some without. What should the
>>> boolean be in that case?
>> 
>> I think you'd really want to know which layers do and don't have
>> filters. It might be even more interesting to have a tool like what 'git
>> show-index' is to '*.idx' files, maybe something like 'git show-graph'
>> or 'git show-commit-graph'. Its output would be one line per commit that
>> shows:
>> 
>>  - what layer in the chain it's located at
>>  - its graph_pos
>>  - its generation number
>>  - whether or not it has a Bloom filter
>>  - ???
>> 
>> That would be a useful tool for debugging anyway, even outside of the
>> test suite. It would be even better if we could replace the test-tool
>> with it.
> 
> Yeah, that was exactly what I had in mind, except that I'd make it a
> sub-command of "git commit-graph" ("show" or perhaps "dump").

I loved Junio's initial suggestion and the follow up here.
I was thinking of something like 'git commit-graph verify --verbose' but 
now I agree that a distinct command such as 'show' might be more 
distinct and better communicate the purpose.

I will stick with my poor-man bash/golang script for now to invalidate
the commit-graph (chain or no-chain) as it does the job just fine.

Let me see if I have the capacity to implement 'show' sub-command
after. ^_^!

> 
> -Peff

Cheers,
Son Luong.