view tests/test-rebase-interruptions.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

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > rebase=
  > 
  > [phases]
  > publish=False
  > 
  > [alias]
  > tglog = log -G --template "{rev}: {node|short} '{desc}' {branches}\n"
  > tglogp = log -G --template "{rev}: {node|short} {phase} '{desc}' {branches}\n"
  > EOF


  $ hg init a
  $ cd a

  $ echo A > A
  $ hg ci -Am A
  adding A

  $ echo B > B
  $ hg ci -Am B
  adding B

  $ echo C >> A
  $ hg ci -m C

  $ hg up -q -C 0

  $ echo D >> A
  $ hg ci -m D
  created new head

  $ echo E > E
  $ hg ci -Am E
  adding E

  $ cd ..


Changes during an interruption - continue:

  $ hg clone -q -u . a a1
  $ cd a1

  $ hg tglog
  @  4: ae36e8e3dfd7 'E'
  |
  o  3: 46b37eabc604 'D'
  |
  | o  2: 965c486023db 'C'
  | |
  | o  1: 27547f69f254 'B'
  |/
  o  0: 4a2df7238c3b 'A'
  
Rebasing B onto E:

  $ hg rebase -s 1 -d 4
  rebasing 1:27547f69f254 "B"
  rebasing 2:965c486023db "C"
  merging A
  warning: conflicts while merging A! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see hg resolve, then hg rebase --continue)
  [1]

Force a commit on C during the interruption:

  $ hg up -q -C 2 --config 'extensions.rebase=!'

  $ echo 'Extra' > Extra
  $ hg add Extra
  $ hg ci -m 'Extra' --config 'extensions.rebase=!'

Force this commit onto secret phase

  $ hg phase --force --secret 6

  $ hg tglogp
  @  6: deb5d2f93d8b secret 'Extra'
  |
  | o  5: 45396c49d53b draft 'B'
  | |
  | o  4: ae36e8e3dfd7 draft 'E'
  | |
  | o  3: 46b37eabc604 draft 'D'
  | |
  o |  2: 965c486023db draft 'C'
  | |
  o |  1: 27547f69f254 draft 'B'
  |/
  o  0: 4a2df7238c3b draft 'A'
  
Resume the rebasing:

  $ hg rebase --continue
  already rebased 1:27547f69f254 "B" as 45396c49d53b
  rebasing 2:965c486023db "C"
  merging A
  warning: conflicts while merging A! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see hg resolve, then hg rebase --continue)
  [1]

Solve the conflict and go on:

  $ echo 'conflict solved' > A
  $ rm A.orig
  $ hg resolve -m A
  (no more unresolved files)
  continue: hg rebase --continue

  $ hg rebase --continue
  already rebased 1:27547f69f254 "B" as 45396c49d53b
  rebasing 2:965c486023db "C"
  warning: orphaned descendants detected, not stripping 27547f69f254, 965c486023db

  $ hg tglogp
  o  7: d2d25e26288e draft 'C'
  |
  | o  6: deb5d2f93d8b secret 'Extra'
  | |
  o |  5: 45396c49d53b draft 'B'
  | |
  @ |  4: ae36e8e3dfd7 draft 'E'
  | |
  o |  3: 46b37eabc604 draft 'D'
  | |
  | o  2: 965c486023db draft 'C'
  | |
  | o  1: 27547f69f254 draft 'B'
  |/
  o  0: 4a2df7238c3b draft 'A'
  
  $ cd ..


Changes during an interruption - abort:

  $ hg clone -q -u . a a2
  $ cd a2

  $ hg tglog
  @  4: ae36e8e3dfd7 'E'
  |
  o  3: 46b37eabc604 'D'
  |
  | o  2: 965c486023db 'C'
  | |
  | o  1: 27547f69f254 'B'
  |/
  o  0: 4a2df7238c3b 'A'
  
Rebasing B onto E:

  $ hg rebase -s 1 -d 4
  rebasing 1:27547f69f254 "B"
  rebasing 2:965c486023db "C"
  merging A
  warning: conflicts while merging A! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see hg resolve, then hg rebase --continue)
  [1]

Force a commit on B' during the interruption:

  $ hg up -q -C 5 --config 'extensions.rebase=!'

  $ echo 'Extra' > Extra
  $ hg add Extra
  $ hg ci -m 'Extra' --config 'extensions.rebase=!'

  $ hg tglog
  @  6: 402ee3642b59 'Extra'
  |
  o  5: 45396c49d53b 'B'
  |
  o  4: ae36e8e3dfd7 'E'
  |
  o  3: 46b37eabc604 'D'
  |
  | o  2: 965c486023db 'C'
  | |
  | o  1: 27547f69f254 'B'
  |/
  o  0: 4a2df7238c3b 'A'
  
Abort the rebasing:

  $ hg rebase --abort
  warning: new changesets detected on destination branch, can't strip
  rebase aborted

  $ hg tglog
  @  6: 402ee3642b59 'Extra'
  |
  o  5: 45396c49d53b 'B'
  |
  o  4: ae36e8e3dfd7 'E'
  |
  o  3: 46b37eabc604 'D'
  |
  | o  2: 965c486023db 'C'
  | |
  | o  1: 27547f69f254 'B'
  |/
  o  0: 4a2df7238c3b 'A'
  
  $ cd ..

Changes during an interruption - abort (again):

  $ hg clone -q -u . a a3
  $ cd a3

  $ hg tglogp
  @  4: ae36e8e3dfd7 draft 'E'
  |
  o  3: 46b37eabc604 draft 'D'
  |
  | o  2: 965c486023db draft 'C'
  | |
  | o  1: 27547f69f254 draft 'B'
  |/
  o  0: 4a2df7238c3b draft 'A'
  
Rebasing B onto E:

  $ hg rebase -s 1 -d 4
  rebasing 1:27547f69f254 "B"
  rebasing 2:965c486023db "C"
  merging A
  warning: conflicts while merging A! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see hg resolve, then hg rebase --continue)
  [1]

Change phase on B and B'

  $ hg up -q -C 5 --config 'extensions.rebase=!'
  $ hg phase --public 1
  $ hg phase --public 5
  $ hg phase --secret -f 2

  $ hg tglogp
  @  5: 45396c49d53b public 'B'
  |
  o  4: ae36e8e3dfd7 public 'E'
  |
  o  3: 46b37eabc604 public 'D'
  |
  | o  2: 965c486023db secret 'C'
  | |
  | o  1: 27547f69f254 public 'B'
  |/
  o  0: 4a2df7238c3b public 'A'
  
Abort the rebasing:

  $ hg rebase --abort
  warning: can't clean up public changesets 45396c49d53b
  rebase aborted

  $ hg tglogp
  @  5: 45396c49d53b public 'B'
  |
  o  4: ae36e8e3dfd7 public 'E'
  |
  o  3: 46b37eabc604 public 'D'
  |
  | o  2: 965c486023db secret 'C'
  | |
  | o  1: 27547f69f254 public 'B'
  |/
  o  0: 4a2df7238c3b public 'A'
  
Test rebase interrupted by hooks

  $ hg up 2
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo F > F
  $ hg add F
  $ hg ci -m F

  $ cd ..

(precommit version)

  $ cp -R a3 hook-precommit
  $ cd hook-precommit
  $ hg rebase --source 2 --dest 5 --tool internal:other --config 'hooks.precommit=hg status | grep "M A"'
  rebasing 2:965c486023db "C"
  M A
  rebasing 6:a0b2430ebfb8 "F" (tip)
  abort: precommit hook exited with status 1
  [255]
  $ hg tglogp
  @  7: 401ccec5e39f secret 'C'
  |
  | @  6: a0b2430ebfb8 secret 'F'
  | |
  o |  5: 45396c49d53b public 'B'
  | |
  o |  4: ae36e8e3dfd7 public 'E'
  | |
  o |  3: 46b37eabc604 public 'D'
  | |
  | o  2: 965c486023db secret 'C'
  | |
  | o  1: 27547f69f254 public 'B'
  |/
  o  0: 4a2df7238c3b public 'A'
  
  $ hg rebase --continue
  already rebased 2:965c486023db "C" as 401ccec5e39f
  rebasing 6:a0b2430ebfb8 "F"
  saved backup bundle to $TESTTMP/hook-precommit/.hg/strip-backup/965c486023db-aa6250e7-rebase.hg
  $ hg tglogp
  @  6: 6e92a149ac6b secret 'F'
  |
  o  5: 401ccec5e39f secret 'C'
  |
  o  4: 45396c49d53b public 'B'
  |
  o  3: ae36e8e3dfd7 public 'E'
  |
  o  2: 46b37eabc604 public 'D'
  |
  | o  1: 27547f69f254 public 'B'
  |/
  o  0: 4a2df7238c3b public 'A'
  
  $ cd ..

(pretxncommit version)

  $ cp -R a3 hook-pretxncommit
  $ cd hook-pretxncommit
  $ hg rebase --source 2 --dest 5 --tool internal:other \
  >     --config 'hooks.tonative.pretxncommit=True' --config 'hooks.pretxncommit=hg log -r $HG_NODE | grep "summary:     C"'
  rebasing 2:965c486023db "C"
  summary:     C
  rebasing 6:a0b2430ebfb8 "F" (tip)
  transaction abort!
  rollback completed
  abort: pretxncommit hook exited with status 1
  [255]
  $ hg tglogp
  @  7: 401ccec5e39f secret 'C'
  |
  | @  6: a0b2430ebfb8 secret 'F'
  | |
  o |  5: 45396c49d53b public 'B'
  | |
  o |  4: ae36e8e3dfd7 public 'E'
  | |
  o |  3: 46b37eabc604 public 'D'
  | |
  | o  2: 965c486023db secret 'C'
  | |
  | o  1: 27547f69f254 public 'B'
  |/
  o  0: 4a2df7238c3b public 'A'
  
  $ hg rebase --continue
  already rebased 2:965c486023db "C" as 401ccec5e39f
  rebasing 6:a0b2430ebfb8 "F"
  saved backup bundle to $TESTTMP/hook-pretxncommit/.hg/strip-backup/965c486023db-aa6250e7-rebase.hg
  $ hg tglogp
  @  6: 6e92a149ac6b secret 'F'
  |
  o  5: 401ccec5e39f secret 'C'
  |
  o  4: 45396c49d53b public 'B'
  |
  o  3: ae36e8e3dfd7 public 'E'
  |
  o  2: 46b37eabc604 public 'D'
  |
  | o  1: 27547f69f254 public 'B'
  |/
  o  0: 4a2df7238c3b public 'A'
  
  $ cd ..

(pretxnclose version)

  $ cp -R a3 hook-pretxnclose
  $ cd hook-pretxnclose
  $ hg rebase --source 2 --dest 5 --tool internal:other --config 'hooks.pretxnclose=hg log -r tip | grep "summary:     C"'
  rebasing 2:965c486023db "C"
  summary:     C
  rebasing 6:a0b2430ebfb8 "F" (tip)
  transaction abort!
  rollback completed
  abort: pretxnclose hook exited with status 1
  [255]
  $ hg tglogp
  @  7: 401ccec5e39f secret 'C'
  |
  | @  6: a0b2430ebfb8 secret 'F'
  | |
  o |  5: 45396c49d53b public 'B'
  | |
  o |  4: ae36e8e3dfd7 public 'E'
  | |
  o |  3: 46b37eabc604 public 'D'
  | |
  | o  2: 965c486023db secret 'C'
  | |
  | o  1: 27547f69f254 public 'B'
  |/
  o  0: 4a2df7238c3b public 'A'
  
  $ hg rebase --continue
  already rebased 2:965c486023db "C" as 401ccec5e39f
  rebasing 6:a0b2430ebfb8 "F"
  saved backup bundle to $TESTTMP/hook-pretxnclose/.hg/strip-backup/965c486023db-aa6250e7-rebase.hg
  $ hg tglogp
  @  6: 6e92a149ac6b secret 'F'
  |
  o  5: 401ccec5e39f secret 'C'
  |
  o  4: 45396c49d53b public 'B'
  |
  o  3: ae36e8e3dfd7 public 'E'
  |
  o  2: 46b37eabc604 public 'D'
  |
  | o  1: 27547f69f254 public 'B'
  |/
  o  0: 4a2df7238c3b public 'A'
  
  $ cd ..

Make sure merge state is cleaned up after a no-op rebase merge (issue5494)
  $ hg init repo
  $ cd repo
  $ echo a > a
  $ hg commit -qAm base
  $ echo b >> a
  $ hg commit -qm b
  $ hg up '.^'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo c >> a
  $ hg commit -qm c
  $ hg rebase -s 1 -d 2 --noninteractive
  rebasing 1:fdaca8533b86 "b"
  merging a
  warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see hg resolve, then hg rebase --continue)
  [1]
  $ echo a > a
  $ echo c >> a
  $ hg resolve --mark a
  (no more unresolved files)
  continue: hg rebase --continue
  $ hg rebase --continue
  rebasing 1:fdaca8533b86 "b"
  note: rebase of 1:fdaca8533b86 created no changes to commit
  saved backup bundle to $TESTTMP/repo/.hg/strip-backup/fdaca8533b86-7fd70513-rebase.hg
  $ hg resolve --list
  $ test -d .hg/merge
  [1]
Now try again with --collapse
  $ hg unbundle -q .hg/strip-backup/fdaca8533b86-7fd70513-rebase.hg
  $ hg rebase -s 2 -d 1 --noninteractive --collapse
  rebasing 2:fdaca8533b86 "b" (tip)
  merging a
  warning: conflicts while merging a! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see hg resolve, then hg rebase --continue)
  [1]
  $ echo a > a
  $ echo c >> a
  $ hg resolve --mark a
  (no more unresolved files)
  continue: hg rebase --continue
  $ hg rebase --continue
  rebasing 2:fdaca8533b86 "b" (tip)
  saved backup bundle to $TESTTMP/repo/.hg/strip-backup/fdaca8533b86-7fd70513-rebase.hg
  $ hg resolve --list
  $ test -d .hg/merge
  [1]