view tests/test-convert-svn-source.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 svn svn-bindings

  $ filter_svn_output () {
  >     egrep -v 'Committing|Updating|(^$)' | sed -e 's/done$//' || true
  > }

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > convert =
  > [convert]
  > svn.trunk = mytrunk
  > EOF

  $ svnadmin create svn-repo
  $ SVNREPOPATH=`pwd`/svn-repo
#if windows
  $ SVNREPOURL=file:///`"$PYTHON" -c "import urllib, sys; sys.stdout.write(urllib.quote(sys.argv[1]))" "$SVNREPOPATH"`
#else
  $ SVNREPOURL=file://`"$PYTHON" -c "import urllib, sys; sys.stdout.write(urllib.quote(sys.argv[1]))" "$SVNREPOPATH"`
#endif
  $ INVALIDREVISIONID=svn:x2147622-4a9f-4db4-a8d3-13562ff547b2/proj%20B/mytrunk@1
  $ VALIDREVISIONID=svn:a2147622-4a9f-4db4-a8d3-13562ff547b2/proj%20B/mytrunk/mytrunk@1

Now test that it works with trunk/tags layout, but no branches yet.

Initial svn import

  $ mkdir projB
  $ cd projB
  $ mkdir mytrunk
  $ mkdir tags
  $ cd ..

  $ svn import -m "init projB" projB "$SVNREPOURL/proj%20B" | filter_svn_output | sort
  Adding         projB/mytrunk
  Adding         projB/tags
  Committed revision 1.

Update svn repository

  $ svn co "$SVNREPOURL/proj%20B/mytrunk" B | filter_svn_output
  Checked out revision 1.
  $ cd B
  $ echo hello > 'letter .txt'
  $ svn add 'letter .txt' | filter_svn_output
  A         letter .txt
  $ svn ci -m hello | filter_svn_output
  Adding         letter .txt
  Transmitting file data .
  Committed revision 2.

  $ svn-safe-append.py world 'letter .txt'
  $ svn ci -m world | filter_svn_output
  Sending        letter .txt
  Transmitting file data .
  Committed revision 3.

  $ svn copy -m "tag v0.1" "$SVNREPOURL/proj%20B/mytrunk" "$SVNREPOURL/proj%20B/tags/v0.1" | filter_svn_output
  Committed revision 4.

  $ svn-safe-append.py 'nice day today!' 'letter .txt'
  $ svn ci -m "nice day" | filter_svn_output
  Sending        letter .txt
  Transmitting file data .
  Committed revision 5.
  $ cd ..

Convert to hg once and also test localtimezone option

NOTE: This doesn't check all time zones -- it merely determines that
the configuration option is taking effect.

An arbitrary (U.S.) time zone is used here.  TZ=US/Hawaii is selected
since it does not use DST (unlike other U.S. time zones) and is always
a fixed difference from UTC.

  $ TZ=US/Hawaii hg convert --config convert.localtimezone=True "$SVNREPOURL/proj%20B" B-hg
  initializing destination B-hg repository
  scanning source...
  sorting...
  converting...
  3 init projB
  2 hello
  1 world
  0 nice day
  updating tags

Update svn repository again

  $ cd B
  $ svn-safe-append.py "see second letter" 'letter .txt'
  $ echo "nice to meet you" > letter2.txt
  $ svn add letter2.txt | filter_svn_output
  A         letter2.txt
  $ svn ci -m "second letter" | filter_svn_output
  Sending        letter .txt
  Adding         letter2.txt
  Transmitting file data ..
  Committed revision 6.

  $ svn copy -m "tag v0.2" "$SVNREPOURL/proj%20B/mytrunk" "$SVNREPOURL/proj%20B/tags/v0.2" | filter_svn_output
  Committed revision 7.

  $ svn-safe-append.py "blah-blah-blah" letter2.txt
  $ svn ci -m "work in progress" | filter_svn_output
  Sending        letter2.txt
  Transmitting file data .
  Committed revision 8.
  $ cd ..

  $ hg convert -s svn "$SVNREPOURL/proj%20B/non-existent-path" dest
  initializing destination dest repository
  abort: no revision found in module /proj B/non-existent-path
  [255]

########################################

Test incremental conversion

  $ TZ=US/Hawaii hg convert --config convert.localtimezone=True "$SVNREPOURL/proj%20B" B-hg
  scanning source...
  sorting...
  converting...
  1 second letter
  0 work in progress
  updating tags

  $ cd B-hg
  $ hg log -G --template '{rev} {desc|firstline} date: {date|date} files: {files}\n'
  o  7 update tags date: * +0000 files: .hgtags (glob)
  |
  o  6 work in progress date: * -1000 files: letter2.txt (glob)
  |
  o  5 second letter date: * -1000 files: letter .txt letter2.txt (glob)
  |
  o  4 update tags date: * +0000 files: .hgtags (glob)
  |
  o  3 nice day date: * -1000 files: letter .txt (glob)
  |
  o  2 world date: * -1000 files: letter .txt (glob)
  |
  o  1 hello date: * -1000 files: letter .txt (glob)
  |
  o  0 init projB date: * -1000 files: (glob)
  
  $ hg tags -q
  tip
  v0.2
  v0.1
  $ cd ..

Test filemap
  $ echo 'include letter2.txt' > filemap
  $ hg convert --filemap filemap "$SVNREPOURL/proj%20B/mytrunk" fmap
  initializing destination fmap repository
  scanning source...
  sorting...
  converting...
  5 init projB
  4 hello
  3 world
  2 nice day
  1 second letter
  0 work in progress
  $ hg -R fmap branch -q
  default
  $ hg log -G -R fmap --template '{rev} {desc|firstline} files: {files}\n'
  o  1 work in progress files: letter2.txt
  |
  o  0 second letter files: letter2.txt
  
Convert with --full adds and removes files that didn't change

  $ cd B
  $ echo >> "letter .txt"
  $ svn ci -m 'nothing' | filter_svn_output
  Sending        letter .txt
  Transmitting file data .
  Committed revision 9.
  $ cd ..

  $ echo 'rename letter2.txt letter3.txt' > filemap
  $ hg convert --filemap filemap --full "$SVNREPOURL/proj%20B/mytrunk" fmap
  scanning source...
  sorting...
  converting...
  0 nothing
  $ hg -R fmap st --change tip
  A letter .txt
  A letter3.txt
  R letter2.txt

test invalid splicemap1

  $ cat > splicemap <<EOF
  > $INVALIDREVISIONID $VALIDREVISIONID
  > EOF
  $ hg convert --splicemap splicemap "$SVNREPOURL/proj%20B/mytrunk" smap
  initializing destination smap repository
  abort: splicemap entry svn:x2147622-4a9f-4db4-a8d3-13562ff547b2/proj%20B/mytrunk@1 is not a valid revision identifier
  [255]

Test stop revision
  $ hg convert --rev 1 "$SVNREPOURL/proj%20B/mytrunk" stoprev
  initializing destination stoprev repository
  scanning source...
  sorting...
  converting...
  0 init projB
  $ hg -R stoprev branch -q
  default

Check convert_revision extra-records.
This is also the only place testing more than one extra field in a revision.

  $ cd stoprev
  $ hg tip --debug | grep extra
  extra:       branch=default
  extra:       convert_revision=svn:........-....-....-....-............/proj B/mytrunk@1 (re)
  $ cd ..

Test converting empty heads (issue3347).
Also tests getting logs directly without debugsvnlog.

  $ svnadmin create svn-empty
  $ svnadmin load -q svn-empty < "$TESTDIR/svn/empty.svndump"
  $ hg --config convert.svn.trunk= --config convert.svn.debugsvnlog=0 convert svn-empty
  assuming destination svn-empty-hg
  initializing destination svn-empty-hg repository
  scanning source...
  sorting...
  converting...
  1 init projA
  0 adddir
  $ hg --config convert.svn.trunk= convert "$SVNREPOURL/../svn-empty/trunk"
  assuming destination trunk-hg
  initializing destination trunk-hg repository
  scanning source...
  sorting...
  converting...
  1 init projA
  0 adddir

Test that a too-new repository format is properly rejected:
  $ mv svn-empty/format format
  $ echo 999 > svn-empty/format
It's important that this command explicitly specify svn, otherwise it
can have surprising side effects (like falling back to a perforce
depot that can be seen from the test environment and slurping from that.)
  $ hg convert --source-type svn svn-empty this-will-fail
  initializing destination this-will-fail repository
  file:/*/$TESTTMP/svn-empty does not look like a Subversion repository to libsvn version 1.*.* (glob)
  abort: svn-empty: missing or unsupported repository
  [255]
  $ mv format svn-empty/format

enable svn subrepos

  $ cat >> $HGRCPATH <<EOF
  > [subrepos]
  > svn:allowed = true
  > EOF

try converting when we have an svn subrepo and a merge in hg superrepo (issue5657)

  $ cd "$TESTTMP"
  $ hg init withmerge
  $ cd withmerge
  $ echo "subrepo = [svn]$SVNREPOURL" >.hgsub
  $ hg add .hgsub
  $ svn checkout "$SVNREPOURL" subrepo | sort
  A    subrepo/proj B
  A    subrepo/proj B/mytrunk
  A    subrepo/proj B/mytrunk/letter .txt
  A    subrepo/proj B/mytrunk/letter2.txt
  A    subrepo/proj B/tags
  A    subrepo/proj B/tags/v0.1
  A    subrepo/proj B/tags/v0.1/letter .txt
  A    subrepo/proj B/tags/v0.2
  A    subrepo/proj B/tags/v0.2/letter .txt
  A    subrepo/proj B/tags/v0.2/letter2.txt
  Checked out revision 9.
  $ hg ci -m "Adding svn subrepo"
  $ touch file1.txt
  $ hg add file1.txt
  $ hg ci -m "Adding file1"
  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ touch file2.txt
  $ hg add file2.txt
  $ hg ci -m "Adding file2"
  created new head
  $ hg merge 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -m "merged"
  $ cd ..
  $ hg --config extensions.convert= convert withmerge withmerge-converted
  initializing destination withmerge-converted repository
  scanning source...
  sorting...
  converting...
  3 Adding svn subrepo
  2 Adding file1
  1 Adding file2
  0 merged
  $ cd withmerge-converted
  $ hg up | sort
  4 files updated, 0 files merged, 0 files removed, 0 files unresolved
  A    subrepo/proj B
  A    subrepo/proj B/mytrunk
  A    subrepo/proj B/mytrunk/letter .txt
  A    subrepo/proj B/mytrunk/letter2.txt
  A    subrepo/proj B/tags
  A    subrepo/proj B/tags/v0.1
  A    subrepo/proj B/tags/v0.1/letter .txt
  A    subrepo/proj B/tags/v0.2
  A    subrepo/proj B/tags/v0.2/letter .txt
  A    subrepo/proj B/tags/v0.2/letter2.txt
  Checked out revision 9.
  $ ls
  file1.txt
  file2.txt
  subrepo