view tests/test-git-export.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

  $ hg init
  $ echo start > start
  $ hg ci -Amstart
  adding start

New file:

  $ mkdir dir1
  $ echo new > dir1/new
  $ hg ci -Amnew
  adding dir1/new
  $ hg diff --git -r 0
  diff --git a/dir1/new b/dir1/new
  new file mode 100644
  --- /dev/null
  +++ b/dir1/new
  @@ -0,0 +1,1 @@
  +new

Copy:

  $ mkdir dir2
  $ hg cp dir1/new dir1/copy
  $ echo copy1 >> dir1/copy
  $ hg cp dir1/new dir2/copy
  $ echo copy2 >> dir2/copy
  $ hg ci -mcopy
  $ hg diff --git -r 1:tip
  diff --git a/dir1/new b/dir1/copy
  copy from dir1/new
  copy to dir1/copy
  --- a/dir1/new
  +++ b/dir1/copy
  @@ -1,1 +1,2 @@
   new
  +copy1
  diff --git a/dir1/new b/dir2/copy
  copy from dir1/new
  copy to dir2/copy
  --- a/dir1/new
  +++ b/dir2/copy
  @@ -1,1 +1,2 @@
   new
  +copy2

Cross and same-directory copies with a relative root:

  $ hg diff --git --root .. -r 1:tip
  abort: .. not under root '$TESTTMP'
  [255]
  $ hg diff --git --root doesnotexist -r 1:tip
  $ hg diff --git --root . -r 1:tip
  diff --git a/dir1/new b/dir1/copy
  copy from dir1/new
  copy to dir1/copy
  --- a/dir1/new
  +++ b/dir1/copy
  @@ -1,1 +1,2 @@
   new
  +copy1
  diff --git a/dir1/new b/dir2/copy
  copy from dir1/new
  copy to dir2/copy
  --- a/dir1/new
  +++ b/dir2/copy
  @@ -1,1 +1,2 @@
   new
  +copy2
  $ hg diff --git --root dir1 -r 1:tip
  diff --git a/new b/copy
  copy from new
  copy to copy
  --- a/new
  +++ b/copy
  @@ -1,1 +1,2 @@
   new
  +copy1

  $ hg diff --git --root dir2/ -r 1:tip
  diff --git a/copy b/copy
  new file mode 100644
  --- /dev/null
  +++ b/copy
  @@ -0,0 +1,2 @@
  +new
  +copy2

  $ hg diff --git --root dir1 -r 1:tip -I '**/copy'
  diff --git a/new b/copy
  copy from new
  copy to copy
  --- a/new
  +++ b/copy
  @@ -1,1 +1,2 @@
   new
  +copy1

  $ hg diff --git --root dir1 -r 1:tip dir2
  warning: dir2 not inside relative root dir1

  $ hg diff --git --root dir1 -r 1:tip 'dir2/{copy}'
  warning: dir2/{copy} not inside relative root dir1

  $ cd dir1
  $ hg diff --git --root .. -r 1:tip
  diff --git a/dir1/new b/dir1/copy
  copy from dir1/new
  copy to dir1/copy
  --- a/dir1/new
  +++ b/dir1/copy
  @@ -1,1 +1,2 @@
   new
  +copy1
  diff --git a/dir1/new b/dir2/copy
  copy from dir1/new
  copy to dir2/copy
  --- a/dir1/new
  +++ b/dir2/copy
  @@ -1,1 +1,2 @@
   new
  +copy2

  $ hg diff --git --root ../.. -r 1:tip
  abort: ../.. not under root '$TESTTMP'
  [255]
  $ hg diff --git --root ../doesnotexist -r 1:tip
  $ hg diff --git --root .. -r 1:tip
  diff --git a/dir1/new b/dir1/copy
  copy from dir1/new
  copy to dir1/copy
  --- a/dir1/new
  +++ b/dir1/copy
  @@ -1,1 +1,2 @@
   new
  +copy1
  diff --git a/dir1/new b/dir2/copy
  copy from dir1/new
  copy to dir2/copy
  --- a/dir1/new
  +++ b/dir2/copy
  @@ -1,1 +1,2 @@
   new
  +copy2

  $ hg diff --git --root . -r 1:tip
  diff --git a/new b/copy
  copy from new
  copy to copy
  --- a/new
  +++ b/copy
  @@ -1,1 +1,2 @@
   new
  +copy1
  $ hg diff --git --root . -r 1:tip copy
  diff --git a/new b/copy
  copy from new
  copy to copy
  --- a/new
  +++ b/copy
  @@ -1,1 +1,2 @@
   new
  +copy1
  $ hg diff --git --root . -r 1:tip ../dir2
  warning: ../dir2 not inside relative root .
  $ hg diff --git --root . -r 1:tip '../dir2/*'
  warning: ../dir2/* not inside relative root . (glob)
  $ cd ..

Rename:

  $ hg mv dir1/copy dir1/rename1
  $ echo rename1 >> dir1/rename1
  $ hg mv dir2/copy dir1/rename2
  $ echo rename2 >> dir1/rename2
  $ hg ci -mrename
  $ hg diff --git -r 2:tip
  diff --git a/dir1/copy b/dir1/rename1
  rename from dir1/copy
  rename to dir1/rename1
  --- a/dir1/copy
  +++ b/dir1/rename1
  @@ -1,2 +1,3 @@
   new
   copy1
  +rename1
  diff --git a/dir2/copy b/dir1/rename2
  rename from dir2/copy
  rename to dir1/rename2
  --- a/dir2/copy
  +++ b/dir1/rename2
  @@ -1,2 +1,3 @@
   new
   copy2
  +rename2

Cross and same-directory renames with a relative root:

  $ hg diff --root dir1 --git -r 2:tip
  diff --git a/copy b/rename1
  rename from copy
  rename to rename1
  --- a/copy
  +++ b/rename1
  @@ -1,2 +1,3 @@
   new
   copy1
  +rename1
  diff --git a/rename2 b/rename2
  new file mode 100644
  --- /dev/null
  +++ b/rename2
  @@ -0,0 +1,3 @@
  +new
  +copy2
  +rename2

  $ hg diff --root dir2 --git -r 2:tip
  diff --git a/copy b/copy
  deleted file mode 100644
  --- a/copy
  +++ /dev/null
  @@ -1,2 +0,0 @@
  -new
  -copy2

  $ hg diff --root dir1 --git -r 2:tip -I '**/copy'
  diff --git a/copy b/copy
  deleted file mode 100644
  --- a/copy
  +++ /dev/null
  @@ -1,2 +0,0 @@
  -new
  -copy1

  $ hg diff --root dir1 --git -r 2:tip -I '**/rename*'
  diff --git a/copy b/rename1
  copy from copy
  copy to rename1
  --- a/copy
  +++ b/rename1
  @@ -1,2 +1,3 @@
   new
   copy1
  +rename1
  diff --git a/rename2 b/rename2
  new file mode 100644
  --- /dev/null
  +++ b/rename2
  @@ -0,0 +1,3 @@
  +new
  +copy2
  +rename2

Delete:

  $ hg rm dir1/*
  $ hg ci -mdelete
  $ hg diff --git -r 3:tip
  diff --git a/dir1/new b/dir1/new
  deleted file mode 100644
  --- a/dir1/new
  +++ /dev/null
  @@ -1,1 +0,0 @@
  -new
  diff --git a/dir1/rename1 b/dir1/rename1
  deleted file mode 100644
  --- a/dir1/rename1
  +++ /dev/null
  @@ -1,3 +0,0 @@
  -new
  -copy1
  -rename1
  diff --git a/dir1/rename2 b/dir1/rename2
  deleted file mode 100644
  --- a/dir1/rename2
  +++ /dev/null
  @@ -1,3 +0,0 @@
  -new
  -copy2
  -rename2

  $ cat > src <<EOF
  > 1
  > 2
  > 3
  > 4
  > 5
  > EOF
  $ hg ci -Amsrc
  adding src

#if execbit

chmod 644:

  $ chmod +x src
  $ hg ci -munexec
  $ hg diff --git -r 5:tip
  diff --git a/src b/src
  old mode 100644
  new mode 100755

Rename+mod+chmod:

  $ hg mv src dst
  $ chmod -x dst
  $ echo a >> dst
  $ hg ci -mrenamemod
  $ hg diff --git -r 6:tip
  diff --git a/src b/dst
  old mode 100755
  new mode 100644
  rename from src
  rename to dst
  --- a/src
  +++ b/dst
  @@ -3,3 +3,4 @@
   3
   4
   5
  +a

Nonexistent in tip+chmod:

  $ hg diff --git -r 5:6
  diff --git a/src b/src
  old mode 100644
  new mode 100755

#else

Dummy changes when no exec bit, mocking the execbit commit structure

  $ echo change >> src
  $ hg ci -munexec
  $ hg mv src dst
  $ hg ci -mrenamemod

#endif

Binary diff:

  $ cp "$TESTDIR/binfile.bin" .
  $ hg add binfile.bin
  $ hg diff --git > b.diff
  $ cat b.diff
  diff --git a/binfile.bin b/binfile.bin
  new file mode 100644
  index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..37ba3d1c6f17137d9c5f5776fa040caf5fe73ff9
  GIT binary patch
  literal 593
  zc$@)I0<QguP)<h;3K|Lk000e1NJLTq000mG000mO0ssI2kdbIM00009a7bBm000XU
  z000XU0RWnu7ytkO2XskIMF-Uh9TW;VpMjwv0005-Nkl<ZD9@FWPs=e;7{<>W$NUkd
  zX$nnYLt$-$V!?uy+1V%`z&Eh=ah|duER<4|QWhju3gb^nF*8iYobxWG-qqXl=2~5M
  z*IoDB)sG^CfNuoBmqLTVU^<;@nwHP!1wrWd`{(mHo6VNXWtyh{alzqmsH*yYzpvLT
  zLdY<T=ks|woh-`&01!ej#(xbV1f|pI*=%;d-%F*E*X#ZH`4I%6SS+$EJDE&ct=8po
  ziN#{?_j|kD%Cd|oiqds`xm@;oJ-^?NG3Gdqrs?5u*zI;{nogxsx~^|Fn^Y?Gdc6<;
  zfMJ+iF1J`LMx&A2?dEwNW8ClebzPTbIh{@$hS6*`kH@1d%Lo7fA#}N1)oN7`gm$~V
  z+wDx#)OFqMcE{s!JN0-xhG8ItAjVkJwEcb`3WWlJfU2r?;Pd%dmR+q@mSri5q9_W-
  zaR2~ECX?B2w+zELozC0s*6Z~|QG^f{3I#<`?)Q7U-JZ|q5W;9Q8i_=pBuSzunx=U;
  z9C)5jBoYw9^?EHyQl(M}1OlQcCX>lXB*ODN003Z&P17_@)3Pi=i0wb04<W?v-u}7K
  zXmmQA+wDgE!qR9o8jr`%=ab_&uh(l?R=r;Tjiqon91I2-hIu?57~@*4h7h9uORK#=
  fQItJW-{SoTm)8|5##k|m00000NkvXXu0mjf{mKw4
  

Import binary diff:

  $ hg revert binfile.bin
  $ rm binfile.bin
  $ hg import -mfoo b.diff
  applying b.diff
  $ cmp binfile.bin "$TESTDIR/binfile.bin"

Rename binary file:

  $ hg mv binfile.bin renamed.bin
  $ hg diff --git
  diff --git a/binfile.bin b/renamed.bin
  rename from binfile.bin
  rename to renamed.bin

Diff across many revisions:

  $ hg mv dst dst2
  $ hg ci -m 'mv dst dst2'

  $ echo >> start
  $ hg ci -m 'change start'

  $ hg revert -r -2 start
  $ hg mv dst2 dst3
  $ hg ci -m 'mv dst2 dst3; revert start'

  $ hg diff --git -r 9:11
  diff --git a/dst2 b/dst3
  rename from dst2
  rename to dst3

Reversed:

  $ hg diff --git -r 11:9
  diff --git a/dst3 b/dst2
  rename from dst3
  rename to dst2


  $ echo a >> foo
  $ hg add foo
  $ hg ci -m 'add foo'
  $ echo b >> foo
  $ hg ci -m 'change foo'
  $ hg mv foo bar
  $ hg ci -m 'mv foo bar'
  $ echo c >> bar
  $ hg ci -m 'change bar'

File created before r1 and renamed before r2:

  $ hg diff --git -r -3:-1
  diff --git a/foo b/bar
  rename from foo
  rename to bar
  --- a/foo
  +++ b/bar
  @@ -1,2 +1,3 @@
   a
   b
  +c

Reversed:

  $ hg diff --git -r -1:-3
  diff --git a/bar b/foo
  rename from bar
  rename to foo
  --- a/bar
  +++ b/foo
  @@ -1,3 +1,2 @@
   a
   b
  -c

File created in r1 and renamed before r2:

  $ hg diff --git -r -4:-1
  diff --git a/foo b/bar
  rename from foo
  rename to bar
  --- a/foo
  +++ b/bar
  @@ -1,1 +1,3 @@
   a
  +b
  +c

Reversed:

  $ hg diff --git -r -1:-4
  diff --git a/bar b/foo
  rename from bar
  rename to foo
  --- a/bar
  +++ b/foo
  @@ -1,3 +1,1 @@
   a
  -b
  -c

File created after r1 and renamed before r2:

  $ hg diff --git -r -5:-1
  diff --git a/bar b/bar
  new file mode 100644
  --- /dev/null
  +++ b/bar
  @@ -0,0 +1,3 @@
  +a
  +b
  +c

Reversed:

  $ hg diff --git -r -1:-5
  diff --git a/bar b/bar
  deleted file mode 100644
  --- a/bar
  +++ /dev/null
  @@ -1,3 +0,0 @@
  -a
  -b
  -c


Comparing with the working dir:

  $ echo >> start
  $ hg ci -m 'change start again'

  $ echo > created
  $ hg add created
  $ hg ci -m 'add created'

  $ hg mv created created2
  $ hg ci -m 'mv created created2'

  $ hg mv created2 created3

There's a copy in the working dir:

  $ hg diff --git
  diff --git a/created2 b/created3
  rename from created2
  rename to created3

There's another copy between the original rev and the wd:

  $ hg diff --git -r -2
  diff --git a/created b/created3
  rename from created
  rename to created3

The source of the copy was created after the original rev:

  $ hg diff --git -r -3
  diff --git a/created3 b/created3
  new file mode 100644
  --- /dev/null
  +++ b/created3
  @@ -0,0 +1,1 @@
  +
  $ hg ci -m 'mv created2 created3'


  $ echo > brand-new
  $ hg add brand-new
  $ hg ci -m 'add brand-new'
  $ hg mv brand-new brand-new2

Created in parent of wd; renamed in the wd:

  $ hg diff --git
  diff --git a/brand-new b/brand-new2
  rename from brand-new
  rename to brand-new2

Created between r1 and parent of wd; renamed in the wd:

  $ hg diff --git -r -2
  diff --git a/brand-new2 b/brand-new2
  new file mode 100644
  --- /dev/null
  +++ b/brand-new2
  @@ -0,0 +1,1 @@
  +
  $ hg ci -m 'mv brand-new brand-new2'

One file is copied to many destinations and removed:

  $ hg cp brand-new2 brand-new3
  $ hg mv brand-new2 brand-new3-2
  $ hg ci -m 'multiple renames/copies'
  $ hg diff --git -r -2 -r -1
  diff --git a/brand-new2 b/brand-new3
  rename from brand-new2
  rename to brand-new3
  diff --git a/brand-new2 b/brand-new3-2
  copy from brand-new2
  copy to brand-new3-2

Reversed:

  $ hg diff --git -r -1 -r -2
  diff --git a/brand-new3-2 b/brand-new2
  rename from brand-new3-2
  rename to brand-new2
  diff --git a/brand-new3 b/brand-new3
  deleted file mode 100644
  --- a/brand-new3
  +++ /dev/null
  @@ -1,1 +0,0 @@
  -

There should be a trailing TAB if there are spaces in the file name:

  $ echo foo > 'with spaces'
  $ hg add 'with spaces'
  $ hg diff --git
  diff --git a/with spaces b/with spaces
  new file mode 100644
  --- /dev/null
  +++ b/with spaces	
  @@ -0,0 +1,1 @@
  +foo
  $ hg ci -m 'add filename with spaces'

Additions should be properly marked even in the middle of a merge

  $ hg up -r -2
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo "New File" >> inmerge
  $ hg add inmerge
  $ hg ci -m "file in merge"
  created new head
  $ hg up 23
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg merge
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg diff -g
  diff --git a/inmerge b/inmerge
  new file mode 100644
  --- /dev/null
  +++ b/inmerge
  @@ -0,0 +1,1 @@
  +New File