view tests/test-rebase-inmemory.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 symlink execbit
  $ cat << EOF >> $HGRCPATH
  > [extensions]
  > amend=
  > rebase=
  > debugdrawdag=$TESTDIR/drawdag.py
  > strip=
  > [rebase]
  > experimental.inmemory=1
  > [diff]
  > git=1
  > [alias]
  > tglog = log -G --template "{rev}: {node|short} '{desc}'\n"
  > EOF

Rebase a simple DAG:
  $ hg init repo1
  $ cd repo1
  $ hg debugdrawdag <<'EOS'
  > c b
  > |/
  > d
  > |
  > a
  > EOS
  $ hg up -C a
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg tglog
  o  3: 814f6bd05178 'c'
  |
  | o  2: db0e82a16a62 'b'
  |/
  o  1: 02952614a83d 'd'
  |
  @  0: b173517d0057 'a'
  
  $ hg cat -r 3 c
  c (no-eol)
  $ hg cat -r 2 b
  b (no-eol)
  $ hg rebase --debug -r b -d c | grep rebasing
  rebasing in-memory
  rebasing 2:db0e82a16a62 "b" (b)
  $ hg tglog
  o  3: ca58782ad1e4 'b'
  |
  o  2: 814f6bd05178 'c'
  |
  o  1: 02952614a83d 'd'
  |
  @  0: b173517d0057 'a'
  
  $ hg cat -r 3 b
  b (no-eol)
  $ hg cat -r 2 c
  c (no-eol)

Case 2:
  $ hg init repo2
  $ cd repo2
  $ hg debugdrawdag <<'EOS'
  > c b
  > |/
  > d
  > |
  > a
  > EOS

Add a symlink and executable file:
  $ hg up -C c
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ ln -s somefile e
  $ echo f > f
  $ chmod +x f
  $ hg add e f
  $ hg amend -q
  $ hg up -Cq a

Write files to the working copy, and ensure they're still there after the rebase
  $ echo "abc" > a
  $ ln -s def b
  $ echo "ghi" > c
  $ echo "jkl" > d
  $ echo "mno" > e
  $ hg tglog
  o  3: f56b71190a8f 'c'
  |
  | o  2: db0e82a16a62 'b'
  |/
  o  1: 02952614a83d 'd'
  |
  @  0: b173517d0057 'a'
  
  $ hg cat -r 3 c
  c (no-eol)
  $ hg cat -r 2 b
  b (no-eol)
  $ hg cat -r 3 e
  somefile (no-eol)
  $ hg rebase --debug -s b -d a | grep rebasing
  rebasing in-memory
  rebasing 2:db0e82a16a62 "b" (b)
  $ hg tglog
  o  3: fc055c3b4d33 'b'
  |
  | o  2: f56b71190a8f 'c'
  | |
  | o  1: 02952614a83d 'd'
  |/
  @  0: b173517d0057 'a'
  
  $ hg cat -r 2 c
  c (no-eol)
  $ hg cat -r 3 b
  b (no-eol)
  $ hg rebase --debug -s 1 -d 3 | grep rebasing
  rebasing in-memory
  rebasing 1:02952614a83d "d" (d)
  rebasing 2:f56b71190a8f "c"
  $ hg tglog
  o  3: 753feb6fd12a 'c'
  |
  o  2: 09c044d2cb43 'd'
  |
  o  1: fc055c3b4d33 'b'
  |
  @  0: b173517d0057 'a'
  
Ensure working copy files are still there:
  $ cat a
  abc
  $ readlink.py b
  b -> def
  $ cat e
  mno

Ensure symlink and executable files were rebased properly:
  $ hg up -Cq 3
  $ readlink.py e
  e -> somefile
  $ ls -l f | cut -c -10
  -rwxr-xr-x

Rebase the working copy parent
  $ hg up -C 3
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg rebase -r 3 -d 0 --debug | grep rebasing
  rebasing in-memory
  rebasing 3:753feb6fd12a "c" (tip)
  $ hg tglog
  @  3: 844a7de3e617 'c'
  |
  | o  2: 09c044d2cb43 'd'
  | |
  | o  1: fc055c3b4d33 'b'
  |/
  o  0: b173517d0057 'a'
  

Test reporting of path conflicts

  $ hg rm a
  $ mkdir a
  $ touch a/a
  $ hg ci -Am "a/a"
  adding a/a
  $ hg tglog
  @  4: daf7dfc139cb 'a/a'
  |
  o  3: 844a7de3e617 'c'
  |
  | o  2: 09c044d2cb43 'd'
  | |
  | o  1: fc055c3b4d33 'b'
  |/
  o  0: b173517d0057 'a'
  
  $ hg rebase -r . -d 2
  rebasing 4:daf7dfc139cb "a/a" (tip)
  saved backup bundle to $TESTTMP/repo1/repo2/.hg/strip-backup/daf7dfc139cb-fdbfcf4f-rebase.hg

  $ hg tglog
  @  4: c6ad37a4f250 'a/a'
  |
  | o  3: 844a7de3e617 'c'
  | |
  o |  2: 09c044d2cb43 'd'
  | |
  o |  1: fc055c3b4d33 'b'
  |/
  o  0: b173517d0057 'a'
  
  $ echo foo > foo
  $ hg ci -Aqm "added foo"
  $ hg up '.^'
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo bar > bar
  $ hg ci -Aqm "added bar"
  $ hg rm a/a
  $ echo a > a
  $ hg ci -Aqm "added a back!"
  $ hg tglog
  @  7: 855e9797387e 'added a back!'
  |
  o  6: d14530e5e3e6 'added bar'
  |
  | o  5: 9b94b9373deb 'added foo'
  |/
  o  4: c6ad37a4f250 'a/a'
  |
  | o  3: 844a7de3e617 'c'
  | |
  o |  2: 09c044d2cb43 'd'
  | |
  o |  1: fc055c3b4d33 'b'
  |/
  o  0: b173517d0057 'a'
  
  $ hg rebase -r . -d 5
  rebasing 7:855e9797387e "added a back!" (tip)
  saved backup bundle to $TESTTMP/repo1/repo2/.hg/strip-backup/855e9797387e-81ee4c5d-rebase.hg

  $ hg tglog
  @  7: bb3f02be2688 'added a back!'
  |
  | o  6: d14530e5e3e6 'added bar'
  | |
  o |  5: 9b94b9373deb 'added foo'
  |/
  o  4: c6ad37a4f250 'a/a'
  |
  | o  3: 844a7de3e617 'c'
  | |
  o |  2: 09c044d2cb43 'd'
  | |
  o |  1: fc055c3b4d33 'b'
  |/
  o  0: b173517d0057 'a'
  

  $ cd ..

Test dry-run rebasing

  $ hg init repo3
  $ cd repo3
  $ echo a>a
  $ hg ci -Aqma
  $ echo b>b
  $ hg ci -Aqmb
  $ echo c>c
  $ hg ci -Aqmc
  $ echo d>d
  $ hg ci -Aqmd
  $ echo e>e
  $ hg ci -Aqme

  $ hg up 1 -q
  $ echo f>f
  $ hg ci -Amf
  adding f
  created new head
  $ echo g>g
  $ hg ci -Aqmg
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
Make sure it throws error while passing --continue or --abort with --dry-run
  $ hg rebase -s 2 -d 6 -n --continue
  abort: cannot specify both --dry-run and --continue
  [255]
  $ hg rebase -s 2 -d 6 -n --abort
  abort: cannot specify both --dry-run and --abort
  [255]

Check dryrun gives correct results when there is no conflict in rebasing
  $ hg rebase -s 2 -d 6 -n
  starting dry-run rebase; repository will not be changed
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  dry-run rebase completed successfully; run without -n/--dry-run to perform this rebase

  $ hg diff
  $ hg status

  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
Check dryrun working with --collapse when there is no conflict
  $ hg rebase -s 2 -d 6 -n --collapse
  starting dry-run rebase; repository will not be changed
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  dry-run rebase completed successfully; run without -n/--dry-run to perform this rebase

Check dryrun gives correct results when there is conflict in rebasing
Make a conflict:
  $ hg up 6 -q
  $ echo conflict>e
  $ hg ci -Aqm "conflict with e"
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  7:d2c195b28050 test
  |  conflict with e
  |
  o  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
  $ hg rebase -s 2 -d 7 -n
  starting dry-run rebase; repository will not be changed
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  merging e
  transaction abort!
  rollback completed
  hit a merge conflict
  [1]
  $ hg diff
  $ hg status
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  7:d2c195b28050 test
  |  conflict with e
  |
  o  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
Check dryrun working with --collapse when there is conflicts
  $ hg rebase -s 2 -d 7 -n --collapse
  starting dry-run rebase; repository will not be changed
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  merging e
  hit a merge conflict
  [1]

In-memory rebase that fails due to merge conflicts

  $ hg rebase -s 2 -d 7
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  merging e
  transaction abort!
  rollback completed
  hit merge conflicts; re-running rebase without in-memory merge
  rebase aborted
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  merging e
  warning: conflicts while merging e! (edit, then use 'hg resolve --mark')
  unresolved conflicts (see hg resolve, then hg rebase --continue)
  [1]

==========================
Test for --confirm option|
==========================
  $ cd ..
  $ hg clone repo3 repo4 -q
  $ cd repo4
  $ hg strip 7 -q
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
Check it gives error when both --dryrun and --confirm is used:
  $ hg rebase -s 2 -d . --confirm --dry-run
  abort: cannot specify both --confirm and --dry-run
  [255]
  $ hg rebase -s 2 -d . --confirm --abort
  abort: cannot specify both --confirm and --abort
  [255]
  $ hg rebase -s 2 -d . --confirm --continue
  abort: cannot specify both --confirm and --continue
  [255]

Test --confirm option when there are no conflicts:
  $ hg rebase -s 2 -d . --keep --config ui.interactive=True --confirm << EOF
  > n
  > EOF
  starting in-memory rebase
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  rebase completed successfully
  apply changes (yn)? n
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
  $ hg rebase -s 2 -d . --keep --config ui.interactive=True --confirm << EOF
  > y
  > EOF
  starting in-memory rebase
  rebasing 2:177f92b77385 "c"
  rebasing 3:055a42cdd887 "d"
  rebasing 4:e860deea161a "e"
  rebase completed successfully
  apply changes (yn)? y
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  o  9:9fd28f55f6dc test
  |  e
  |
  o  8:12cbf031f469 test
  |  d
  |
  o  7:c83b1da5b1ae test
  |  c
  |
  @  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
Test --confirm option when there is a conflict
  $ hg up tip -q
  $ echo ee>e
  $ hg ci --amend -m "conflict with e" -q
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  9:906d72f66a59 test
  |  conflict with e
  |
  o  8:12cbf031f469 test
  |  d
  |
  o  7:c83b1da5b1ae test
  |  c
  |
  o  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
  $ hg rebase -s 4 -d . --keep --confirm
  starting in-memory rebase
  rebasing 4:e860deea161a "e"
  merging e
  hit a merge conflict
  [1]
  $ hg log -G --template "{rev}:{short(node)} {person(author)}\n{firstline(desc)} {topic}\n\n"
  @  9:906d72f66a59 test
  |  conflict with e
  |
  o  8:12cbf031f469 test
  |  d
  |
  o  7:c83b1da5b1ae test
  |  c
  |
  o  6:baf10c5166d4 test
  |  g
  |
  o  5:6343ca3eff20 test
  |  f
  |
  | o  4:e860deea161a test
  | |  e
  | |
  | o  3:055a42cdd887 test
  | |  d
  | |
  | o  2:177f92b77385 test
  |/   c
  |
  o  1:d2ae7f538514 test
  |  b
  |
  o  0:cb9a9f314b8b test
     a
  
#if execbit

Test a metadata-only in-memory merge
  $ cd $TESTTMP
  $ hg init no_exception
  $ cd no_exception
# Produce the following graph:
#   o  'add +x to foo.txt'
#   | o  r1  (adds bar.txt, just for something to rebase to)
#   |/
#   o  r0   (adds foo.txt, no +x)
  $ echo hi > foo.txt
  $ hg ci -qAm r0
  $ echo hi > bar.txt
  $ hg ci -qAm r1
  $ hg co -qr ".^"
  $ chmod +x foo.txt
  $ hg ci -qAm 'add +x to foo.txt'
issue5960: this was raising an AttributeError exception
  $ hg rebase -r . -d 1
  rebasing 2:539b93e77479 "add +x to foo.txt" (tip)
  saved backup bundle to $TESTTMP/no_exception/.hg/strip-backup/*.hg (glob)
  $ hg diff -c tip
  diff --git a/foo.txt b/foo.txt
  old mode 100644
  new mode 100755

#endif