view tests/test-convert-mtn.t @ 40326:fed697fa1734

sqlitestore: file storage backend using SQLite

This commit provides an extension which uses SQLite to store file
data (as opposed to revlogs).

As the inline documentation describes, there are still several
aspects to the extension that are incomplete. But it's a start.
The extension does support basic clone, checkout, and commit
workflows, which makes it suitable for simple use cases.

One notable missing feature is support for "bundlerepos." This is
probably responsible for the most test failures when the extension
is activated as part of the test suite.

All revision data is stored in SQLite. Data is stored as zstd
compressed chunks (default if zstd is available), zlib compressed
chunks (default if zstd is not available), or raw chunks (if
configured or if a compressed delta is not smaller than the raw
delta). This makes things very similar to revlogs.

Unlike revlogs, the extension doesn't yet enforce a limit on delta
chain length. This is an obvious limitation and should be addressed.
This is somewhat mitigated by the use of zstd, which is much faster
than zlib to decompress.

There is a dedicated table for storing deltas. Deltas are stored
by the SHA-1 hash of their uncompressed content. The "fileindex" table
has columns that reference the delta for each revision and the base
delta that delta should be applied against. A recursive SQL query
is used to resolve the delta chain along with the delta data.

By storing deltas by hash, we are able to de-duplicate delta storage!
With revlogs, the same deltas in different revlogs would result in
duplicate storage of that delta. In this scheme, inserting the
duplicate delta is a no-op and delta chains simply reference the
existing delta.

When initially implementing this extension, I did not have
content-indexed deltas and deltas could be duplicated across files
(just like revlogs). When I implemented content-indexed deltas, the
size of the SQLite database for a full clone of mozilla-unified
dropped:

before: 2,554,261,504 bytes
after:  2,488,754,176 bytes

Surprisingly, this is still larger than the bytes size of revlog
files:

revlog files: 2,104,861,230 bytes
du -b:        2,254,381,614

I would have expected storage to be smaller since we're not limiting
delta chain length and since we're using zstd instead of zlib. I
suspect the SQLite indexes and per-column overhead account for the
bulk of the differences. (Keep in mind that revlog uses a 64-byte
packed struct for revision index data and deltas are stored without
padding. Aside from the 12 unused bytes in the 32 byte node field,
revlogs are pretty efficient.) Another source of overhead is file
name storage. With revlogs, file names are stored in the filesystem.
But with SQLite, we need to store file names in the database. This is
roughly equivalent to the size of the fncache file, which for the
mozilla-unified repository is ~34MB.

Since the SQLite database isn't append-only and since delta chains
can reference any delta, this opens some interesting possibilities.
For example, we could store deltas in reverse, such that fulltexts
are stored for newer revisions and deltas are applied to reconstruct
older revisions. This is likely a more optimal storage strategy for
version control, as new data tends to be more frequently accessed
than old data. We would obviously need wire protocol support for
transferring revision data from newest to oldest. And we would
probably need some kind of mechanism for "re-encoding" stores. But
it should be doable.

This extension is very much experimental quality. There are a handful
of features that don't work. It probably isn't suitable for day-to-day
use. But it could be used in limited cases (e.g. read-only checkouts
like in CI). And it is also a good proving ground for alternate
storage backends. As we continue to define interfaces for all things
storage, it will be useful to have a viable alternate storage backend
to see how things shake out in practice.

test-storage.py passes on Python 2 and introduces no new test failures on
Python 3. Having the storage-level unit tests has proved to be insanely
useful when developing this extension. Those tests caught numerous bugs
during development and I'm convinced this style of testing is the way
forward for ensuring alternate storage backends work as intended. Of
course, test coverage isn't close to what it needs to be. But it is
a start. And what coverage we have gives me confidence that basic store
functionality is implemented properly.

Differential Revision: https://phab.mercurial-scm.org/D4928

#require mtn

Monotone directory is called .monotone on *nix and monotone
on Windows.

#if windows

  $ mtndir=monotone

#else

  $ mtndir=.monotone

#endif

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "convert=" >> $HGRCPATH

Windows version of monotone home

  $ APPDATA=$HOME; export APPDATA

tedious monotone keys configuration
The /dev/null redirection is necessary under Windows, or
it complains about home directory permissions

  $ mtn --quiet genkey [e-mail] 1>/dev/null 2>&1 <<EOF
  > passphrase
  > passphrase
  > EOF
  $ cat >> $HOME/$mtndir/monotonerc <<EOF
  > function get_passphrase(keypair_id)
  >     return "passphrase"
  > end
  > EOF

create monotone repository

  $ mtn db init --db=repo.mtn
  $ mtn --db=repo.mtn --branch=com.selenic.test setup workingdir
  $ cd workingdir
  $ echo a > a
  $ mkdir dir
  $ echo b > dir/b
  $ echo d > dir/d
  $ "$PYTHON" -c 'open("bin", "wb").write(b"a\\x00b") and None'
  $ echo c > c
  $ mtn add a dir/b dir/d c bin
  mtn: adding 'a' to workspace manifest
  mtn: adding 'bin' to workspace manifest
  mtn: adding 'c' to workspace manifest
  mtn: adding 'dir' to workspace manifest
  mtn: adding 'dir/b' to workspace manifest
  mtn: adding 'dir/d' to workspace manifest
  $ mtn ci -m initialize
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision 0f6e5e4f2e7d2a8ef312408f57618abf026afd90

update monotone working directory

  $ mtn mv a dir/a
  mtn: skipping 'dir', already accounted for in workspace
  mtn: renaming 'a' to 'dir/a' in workspace manifest
  $ echo a >> dir/a
  $ echo b >> dir/b
  $ mtn drop c
  mtn: dropping 'c' from workspace manifest
  $ "$PYTHON" -c 'open("bin", "wb").write(b"b\\x00c") and None'
  $ mtn ci -m update1
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision 51d0a982464573a2a2cf5ee2c9219c652aaebeff
  $ cd ..

convert once

  $ hg convert -s mtn repo.mtn
  assuming destination repo.mtn-hg
  initializing destination repo.mtn-hg repository
  scanning source...
  sorting...
  converting...
  1 initialize
  0 update1
  $ cd workingdir
  $ echo e > e
  $ mtn add e
  mtn: adding 'e' to workspace manifest
  $ mtn drop dir/b
  mtn: dropping 'dir/b' from workspace manifest
  $ mtn mv bin bin2
  mtn: renaming 'bin' to 'bin2' in workspace manifest
  $ mtn ci -m 'update2 "with" quotes'
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision ebe58335d85d8cb176b6d0a12be04f5314b998da

test directory move

  $ mkdir -p dir1/subdir1
  $ mkdir -p dir1/subdir2_other
  $ echo file1 > dir1/subdir1/file1
  $ echo file2 > dir1/subdir2_other/file1
  $ mtn add dir1/subdir1/file1 dir1/subdir2_other/file1
  mtn: adding 'dir1' to workspace manifest
  mtn: adding 'dir1/subdir1' to workspace manifest
  mtn: adding 'dir1/subdir1/file1' to workspace manifest
  mtn: adding 'dir1/subdir2_other' to workspace manifest
  mtn: adding 'dir1/subdir2_other/file1' to workspace manifest
  $ mtn ci -m createdir1
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision a8d62bc04fee4d2936d28e98bbcc81686dd74306
  $ mtn rename dir1/subdir1 dir1/subdir2
  mtn: skipping 'dir1', already accounted for in workspace
  mtn: renaming 'dir1/subdir1' to 'dir1/subdir2' in workspace manifest
  $ mtn ci -m movedir1
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision 2c3d241bbbfe538b1b51d910f5676407e3f4d3a6

test subdirectory move

  $ mtn mv dir dir2
  mtn: renaming 'dir' to 'dir2' in workspace manifest
  $ echo newfile > dir2/newfile
  $ mtn drop dir2/d
  mtn: dropping 'dir2/d' from workspace manifest
  $ mtn add dir2/newfile
  mtn: adding 'dir2/newfile' to workspace manifest
  $ mtn ci -m movedir
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision fdb5a02dae8bfce3a79b3393680af471016e1b4c

Test directory removal with empty directory

  $ mkdir dir2/dir
  $ mkdir dir2/dir/subdir
  $ echo f > dir2/dir/subdir/f
  $ mkdir dir2/dir/emptydir
  $ mtn add --quiet -R dir2/dir
  $ mtn ci -m emptydir
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision 8bbf76d717001d24964e4604739fdcd0f539fc88
  $ mtn drop -R dir2/dir
  mtn: dropping 'dir2/dir/subdir/f' from workspace manifest
  mtn: dropping 'dir2/dir/subdir' from workspace manifest
  mtn: dropping 'dir2/dir/emptydir' from workspace manifest
  mtn: dropping 'dir2/dir' from workspace manifest
  $ mtn ci -m dropdirectory
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision 2323d4bc324e6c82628dc04d47a9fd32ad24e322

test directory and file move

  $ mkdir -p dir3/d1
  $ echo a > dir3/a
  $ mtn add dir3/a dir3/d1
  mtn: adding 'dir3' to workspace manifest
  mtn: adding 'dir3/a' to workspace manifest
  mtn: adding 'dir3/d1' to workspace manifest
  $ mtn ci -m dirfilemove
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision 47b192f720faa622f48c68d1eb075b26d405aa8b
  $ mtn mv dir3/a dir3/d1/a
  mtn: skipping 'dir3/d1', already accounted for in workspace
  mtn: renaming 'dir3/a' to 'dir3/d1/a' in workspace manifest
  $ mtn mv dir3/d1 dir3/d2
  mtn: skipping 'dir3', already accounted for in workspace
  mtn: renaming 'dir3/d1' to 'dir3/d2' in workspace manifest
  $ mtn ci -m dirfilemove2
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision 8b543a400d3ee7f6d4bb1835b9b9e3747c8cb632

test directory move into another directory move

  $ mkdir dir4
  $ mkdir dir5
  $ echo a > dir4/a
  $ mtn add dir4/a dir5
  mtn: adding 'dir4' to workspace manifest
  mtn: adding 'dir4/a' to workspace manifest
  mtn: adding 'dir5' to workspace manifest
  $ mtn ci -m dirdirmove
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision 466e0b2afc7a55aa2b4ab2f57cb240bb6cd66fc7
  $ mtn mv dir5 dir6
  mtn: renaming 'dir5' to 'dir6' in workspace manifest
  $ mtn mv dir4 dir6/dir4
  mtn: skipping 'dir6', already accounted for in workspace
  mtn: renaming 'dir4' to 'dir6/dir4' in workspace manifest
  $ mtn ci -m dirdirmove2
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision 3d1f77ebad0c23a5d14911be3b670f990991b749

test diverging directory moves

  $ mkdir -p dir7/dir9/dir8
  $ echo a > dir7/dir9/dir8/a
  $ echo b > dir7/dir9/b
  $ echo c > dir7/c
  $ mtn add -R dir7
  mtn: adding 'dir7' to workspace manifest
  mtn: adding 'dir7/c' to workspace manifest
  mtn: adding 'dir7/dir9' to workspace manifest
  mtn: adding 'dir7/dir9/b' to workspace manifest
  mtn: adding 'dir7/dir9/dir8' to workspace manifest
  mtn: adding 'dir7/dir9/dir8/a' to workspace manifest
  $ mtn ci -m divergentdirmove
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision 08a08511f18b428d840199b062de90d0396bc2ed
  $ mtn mv dir7 dir7-2
  mtn: renaming 'dir7' to 'dir7-2' in workspace manifest
  $ mtn mv dir7-2/dir9 dir9-2
  mtn: renaming 'dir7-2/dir9' to 'dir9-2' in workspace manifest
  $ mtn mv dir9-2/dir8 dir8-2
  mtn: renaming 'dir9-2/dir8' to 'dir8-2' in workspace manifest
  $ mtn ci -m divergentdirmove2
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision 4a736634505795f17786fffdf2c9cbf5b11df6f6

test large file support (> 32kB)

  >>> fp = open('large-file', 'wb')
  >>> for x in range(10000): fp.write(b'%d\n' % x) and None
  >>> fp.close()
  $ md5sum.py large-file
  5d6de8a95c3b6bf9e0ffb808ba5299c1  large-file
  $ mtn add large-file
  mtn: adding 'large-file' to workspace manifest
  $ mtn ci -m largefile
  mtn: beginning commit on branch 'com.selenic.test'
  mtn: committed revision f0a20fecd10dc4392d18fe69a03f1f4919d3387b

test suspending (closing a branch)

  $ mtn suspend f0a20fecd10dc4392d18fe69a03f1f4919d3387b 2> /dev/null
  $ cd ..

convert incrementally

  $ hg convert -s mtn repo.mtn
  assuming destination repo.mtn-hg
  scanning source...
  sorting...
  converting...
  12 update2 "with" quotes
  11 createdir1
  10 movedir1
  9 movedir
  8 emptydir
  7 dropdirectory
  6 dirfilemove
  5 dirfilemove2
  4 dirdirmove
  3 dirdirmove2
  2 divergentdirmove
  1 divergentdirmove2
  0 largefile
  $ glog()
  > {
  >     hg log -G --template '{rev} "{desc|firstline}" files: {files}\n' "$@"
  > }
  $ cd repo.mtn-hg
  $ hg up -C
  12 files updated, 0 files merged, 0 files removed, 0 files unresolved
  no open descendant heads on branch "com.selenic.test", updating to a closed head
  (committing will reopen branch "com.selenic.test")
  $ glog
  @  14 "largefile" files: large-file
  |
  o  13 "divergentdirmove2" files: dir7-2/c dir7/c dir7/dir9/b dir7/dir9/dir8/a dir8-2/a dir9-2/b
  |
  o  12 "divergentdirmove" files: dir7/c dir7/dir9/b dir7/dir9/dir8/a
  |
  o  11 "dirdirmove2" files: dir4/a dir6/dir4/a
  |
  o  10 "dirdirmove" files: dir4/a
  |
  o  9 "dirfilemove2" files: dir3/a dir3/d2/a
  |
  o  8 "dirfilemove" files: dir3/a
  |
  o  7 "dropdirectory" files: dir2/dir/subdir/f
  |
  o  6 "emptydir" files: dir2/dir/subdir/f
  |
  o  5 "movedir" files: dir/a dir/d dir2/a dir2/newfile
  |
  o  4 "movedir1" files: dir1/subdir1/file1 dir1/subdir2/file1
  |
  o  3 "createdir1" files: dir1/subdir1/file1 dir1/subdir2_other/file1
  |
  o  2 "update2 "with" quotes" files: bin bin2 dir/b e
  |
  o  1 "update1" files: a bin c dir/a dir/b
  |
  o  0 "initialize" files: a bin c dir/b dir/d
  

manifest

  $ hg manifest
  bin2
  dir1/subdir2/file1
  dir1/subdir2_other/file1
  dir2/a
  dir2/newfile
  dir3/d2/a
  dir6/dir4/a
  dir7-2/c
  dir8-2/a
  dir9-2/b
  e
  large-file

contents

  $ cat dir2/a
  a
  a
  $ test -d dir2/dir && echo 'removed dir2/dir is still there!'
  [1]

file move

  $ hg log -v -C -r 1 | grep copies
  copies:      dir/a (a)

check directory move

  $ hg manifest -r 4
  bin2
  dir/a
  dir/d
  dir1/subdir2/file1
  dir1/subdir2_other/file1
  e
  $ test -d dir1/subdir2 || echo 'new dir1/subdir2 does not exist!'
  $ test -d dir1/subdir1 && echo 'renamed dir1/subdir1 is still there!'
  [1]
  $ hg log -v -C -r 4 | grep copies
  copies:      dir1/subdir2/file1 (dir1/subdir1/file1)

check file remove with directory move

  $ hg manifest -r 5
  bin2
  dir1/subdir2/file1
  dir1/subdir2_other/file1
  dir2/a
  dir2/newfile
  e

check file move with directory move

  $ hg manifest -r 9
  bin2
  dir1/subdir2/file1
  dir1/subdir2_other/file1
  dir2/a
  dir2/newfile
  dir3/d2/a
  e

check file directory directory move

  $ hg manifest -r 11
  bin2
  dir1/subdir2/file1
  dir1/subdir2_other/file1
  dir2/a
  dir2/newfile
  dir3/d2/a
  dir6/dir4/a
  e

check divergent directory moves

  $ hg manifest -r 13
  bin2
  dir1/subdir2/file1
  dir1/subdir2_other/file1
  dir2/a
  dir2/newfile
  dir3/d2/a
  dir6/dir4/a
  dir7-2/c
  dir8-2/a
  dir9-2/b
  e

test large file support (> 32kB)

  $ md5sum.py large-file
  5d6de8a95c3b6bf9e0ffb808ba5299c1  large-file

check branch closing

  $ hg branches -a
  $ hg branches -c
  com.selenic.test              14:* (closed) (glob)