In an environment where the multi-pack-index is useful, it is due
to many pack-files and an inability to repack the object store
into a single pack-file. However, it is likely that many of these
pack-files are rather small, and could be repacked into a slightly
larger pack-file without too much effort. It may also be important
to ensure the object store is highly available and the repack
operation does not interrupt concurrent git commands.
Introduce a 'repack' subcommand to 'git multi-pack-index' that
takes a '--batch-size' option. The subcommand will inspect the
multi-pack-index for referenced pack-files whose size is smaller
than the batch size, until collecting a list of pack-files whose
sizes sum to larger than the batch size. Then, a new pack-file
will be created containing the objects from those pack-files that
are referenced by the multi-pack-index. The resulting pack is
likely to actually be smaller than the batch size due to
compression and the fact that there may be objects in the pack-
files that have duplicate copies in other pack-files.
The current change introduces the command-line arguments, and we
add a test that ensures we parse these options properly. Since
we specify a small batch size, we will guarantee that future
implementations do not change the list of pack-files.
In addition, we hard-code the modified times of the packs in
the pack directory to ensure the list of packs sorted by modified
time matches the order if sorted by size (ascending). This will
be important in a future test.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The multi-pack-index tracks objects in a collection of pack-files.
Only one copy of each object is indexed, using the modified time
of the pack-files to determine tie-breakers. It is possible to
have a pack-file with no referenced objects because all objects
have a duplicate in a newer pack-file.
Introduce a new 'expire' subcommand to the multi-pack-index builtin.
This subcommand will delete these unused pack-files and rewrite the
multi-pack-index to no longer refer to those files. More details
about the specifics will follow as the method is implemented.
Add a test that verifies the 'expire' subcommand is correctly wired,
but will still be valid when the verb is implemented. Specifically,
create a set of packs that should all have referenced objects and
should not be removed during an 'expire' operation. The packs are
created carefully to ensure they have a specific order when sorted
by size. This will be important in a later test.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Much of the multi-pack-index code focuses on the multi_pack_index
struct, and so we only pass a pointer to the current one. However,
we will insert a dependency on the packed_git linked list in a
future change, so we will need a repository reference. Inserting
these parameters is a significant enough change to split out.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A midx file (and the struct we parse from it) contains a list of all of
the covered packfiles, mentioned by their ".idx" names (e.g.,
"pack-1234.idx", etc). And thus calls to midx_contains_pack() expect
callers to provide the idx name.
This works for most of the calls, but the one in open_packed_git_1()
tries to feed a packed_git->pack_name, which is the ".pack" name,
meaning we'll never find a match (even if the pack is covered by the
midx).
We can fix this by converting the ".pack" to ".idx" in the caller.
However, that requires allocating a new string. Instead, let's make
midx_contains_pack() a bit friendlier, and allow it take _either_ the
.pack or .idx variant.
All cleverness in the matching code is credited to René. Bugs are mine.
There's no test here, because while this does fix _a_ bug, it's masked
by another bug in that same caller. That will be covered (with a test)
in the next patch.
Helped-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Tests for the recently introduced multi-pack index machinery.
* ds/test-multi-pack-index:
packfile: close multi-pack-index in close_all_packs
multi-pack-index: define GIT_TEST_MULTI_PACK_INDEX
midx: close multi-pack-index on repack
midx: fix broken free() in close_midx()
The multi-pack-index feature is tested in isolation by
t5319-multi-pack-index.sh, but there are many more interesting
scenarios in the test suite surrounding pack-file data shapes
and interactions. Since the multi-pack-index is an optional
data structure, it does not make sense to include it by default
in those tests.
Instead, add a new GIT_TEST_MULTI_PACK_INDEX environment variable
that enables core.multiPackIndex and writes a multi-pack-index
after each 'git repack' command. This adds extra test coverage
when needed.
There are a few spots in the test suite that need to react to this
change:
* t5319-multi-pack-index.sh: there is a test that checks that
'git repack' deletes the multi-pack-index. Disable the environment
variable to ensure this still happens.
* t5310-pack-bitmaps.sh: One test moves a pack-file from the object
directory to an alternate. This breaks the multi-pack-index, so
delete the multi-pack-index at this point, if it exists.
* t9300-fast-import.sh: One test verifies the number of files in
the .git/objects/pack directory is exactly 8. Exclude the
multi-pack-index from this count so it is still 8 in all cases.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When repacking, we may remove pack-files. This invalidates the
multi-pack-index (if it exists). Previously, we removed the
multi-pack-index file before removing any pack-file. In some cases,
the repack command may load the multi-pack-index into memory. This
may lead to later in-memory references to the non-existent pack-
files.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The multi-pack-index builtin writes multi-pack-index files, and
uses a 'write' verb to do so. Add a 'verify' verb that checks this
file matches the contents of the pack-indexes it replaces.
The current implementation is a no-op, but will be extended in
small increments in later commits.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
If a repo contains a multi-pack-index, then the packed_git list
does not contain the packfiles that are covered by the multi-pack-index.
This is important for doing object lookups, abbreviations, and
approximating object count. However, there are many operations that
really want to iterate over all packfiles.
Create a new 'all_packs' linked list that contains this list, starting
with the packfiles in the multi-pack-index and then continuing along
the packed_git linked list.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A pack-file is 'local' if it is stored within the usual object
directory. If it is stored in an alternate, it is non-local.
Pack-files are stored using a 'pack_local' member in the packed_git
struct. Add a similar 'local' member to the multi_pack_index struct
and 'local' parameters to the methods that load and prepare multi-
pack-indexes.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
If a 'git repack' command replaces existing packfiles, then we must
clear the existing multi-pack-index before moving the packfiles it
references.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Due to how Windows handles replacing a lockfile when there is an open
handle, create the close_midx() method to close the existing midx before
writing the new one.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The core.multiPackIndex config setting controls the multi-pack-
index (MIDX) feature. If false, the setting will disable all reads
from the multi-pack-index file.
Read this config setting in the new prepare_multi_pack_index_one()
which is called during prepare_packed_git(). This check is run once
per repository.
Add comparison commands in t5319-multi-pack-index.sh to check
typical Git behavior remains the same as the config setting is turned
on and off. This currently includes 'git rev-list' and 'git log'
commands to trigger several object database reads. Currently, these
would only catch an error in the prepare_multi_pack_index_one(), but
with later commits will catch errors in object lookups, abbreviations,
and approximate object counts.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The final pair of chunks for the multi-pack-index file stores the object
offsets. We default to using 32-bit offsets as in the pack-index version
1 format, but if there exists an offset larger than 32-bits, we use a
trick similar to the pack-index version 2 format by storing all offsets
at least 2^31 in a 64-bit table; we use the 32-bit table to point into
that 64-bit table as necessary.
We only store these 64-bit offsets if necessary, so create a test that
manipulates a version 2 pack-index to fake a large offset. This allows
us to test that the large offset table is created, but the data does not
match the actual packfile offsets. The multi-pack-index offset does match
the (corrupted) pack-index offset, so a future feature will compare these
offsets during a 'verify' step.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The multi-pack-index needs to track which packfiles it indexes. Store
these in our first required chunk. Since filenames are not well
structured, add padding to keep good alignment in later chunks.
Modify the 'git multi-pack-index read' subcommand to output the
existence of the pack-file name chunk. Modify t5319-multi-pack-index.sh
to reflect this new output and the new expected number of chunks.
Defense in depth: A pattern we are using in the multi-pack-index feature
is to verify the data as we write it. We want to ensure we never write
invalid data to the multi-pack-index. There are many checks that verify
that the values we are writing fit the format definitions. This mainly
helps developers while working on the feature, but it can also identify
issues that only appear when dealing with very large data sets. These
large sets are hard to encode into test cases.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Create a new multi_pack_index struct for loading multi-pack-indexes into
memory. Create a test-tool builtin for reading basic information about
that multi-pack-index to verify the correct data is written.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In anticipation of writing multi-pack-indexes, add a skeleton
'git multi-pack-index write' subcommand and send the options to a
write_midx_file() method. Also create a skeleton test script that
tests the 'write' subcommand.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
