view tests/test-merge1.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 <<EOF > merge
  > from __future__ import print_function
  > import sys, os
  > 
  > try:
  >     import msvcrt
  >     msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY)
  >     msvcrt.setmode(sys.stderr.fileno(), os.O_BINARY)
  > except ImportError:
  >     pass
  > 
  > print("merging for", os.path.basename(sys.argv[1]))
  > EOF
  $ HGMERGE="$PYTHON ../merge"; export HGMERGE

  $ hg init t
  $ cd t
  $ echo This is file a1 > a
  $ hg add a
  $ hg commit -m "commit #0"
  $ echo This is file b1 > b
  $ hg add b
  $ hg commit -m "commit #1"

  $ hg update 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

Test interrupted updates by having a non-empty dir with the same name as one
of the files in a commit we're updating to

  $ mkdir b && touch b/nonempty
  $ hg up
  abort: Unlinking directory not permitted: *$TESTTMP/t/b* (glob) (windows !)
  abort: Directory not empty: '?\$TESTTMP/t/b'? (re) (no-windows !)
  [255]
  $ hg ci
  abort: last update was interrupted
  (use 'hg update' to get a consistent checkout)
  [255]
  $ hg sum
  parent: 0:538afb845929 
   commit #0
  branch: default
  commit: 1 unknown (interrupted update)
  update: 1 new changesets (update)
  phases: 2 draft

  $ rm b/nonempty

  $ hg up
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg sum
  parent: 1:b8bb4a988f25 tip
   commit #1
  branch: default
  commit: (clean)
  update: (current)
  phases: 2 draft

Prepare a basic merge

  $ hg up 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo This is file c1 > c
  $ hg add c
  $ hg commit -m "commit #2"
  created new head
  $ echo This is file b1 > b
no merges expected
  $ hg merge -P 1
  changeset:   1:b8bb4a988f25
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     commit #1
  
  $ hg merge 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg diff --nodates
  diff -r 49035e18a8e6 b
  --- /dev/null
  +++ b/b
  @@ -0,0 +1,1 @@
  +This is file b1
  $ hg status
  M b
  $ cd ..; rm -r t

  $ hg init t
  $ cd t
  $ echo This is file a1 > a
  $ hg add a
  $ hg commit -m "commit #0"
  $ echo This is file b1 > b
  $ hg add b
  $ hg commit -m "commit #1"

  $ hg update 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo This is file c1 > c
  $ hg add c
  $ hg commit -m "commit #2"
  created new head
  $ echo This is file b2 > b
merge should fail
  $ hg merge 1
  b: untracked file differs
  abort: untracked files in working directory differ from files in requested revision
  [255]

#if symlink
symlinks to directories should be treated as regular files (issue5027)
  $ rm b
  $ ln -s 'This is file b2' b
  $ hg merge 1
  b: untracked file differs
  abort: untracked files in working directory differ from files in requested revision
  [255]
symlinks shouldn't be followed
  $ rm b
  $ echo This is file b1 > .hg/b
  $ ln -s .hg/b b
  $ hg merge 1
  b: untracked file differs
  abort: untracked files in working directory differ from files in requested revision
  [255]

  $ rm b
  $ echo This is file b2 > b
#endif

bad config
  $ hg merge 1 --config merge.checkunknown=x
  abort: merge.checkunknown not valid ('x' is none of 'abort', 'ignore', 'warn')
  [255]
this merge should fail
  $ hg merge 1 --config merge.checkunknown=abort
  b: untracked file differs
  abort: untracked files in working directory differ from files in requested revision
  [255]

this merge should warn
  $ hg merge 1 --config merge.checkunknown=warn
  b: replacing untracked file
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat b.orig
  This is file b2
  $ hg up --clean 2
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ mv b.orig b

this merge should silently ignore
  $ cat b
  This is file b2
  $ hg merge 1 --config merge.checkunknown=ignore
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)

merge.checkignored
  $ hg up --clean 1
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ cat >> .hgignore << EOF
  > remoteignored
  > EOF
  $ echo This is file localignored3 > localignored
  $ echo This is file remoteignored3 > remoteignored
  $ hg add .hgignore localignored remoteignored
  $ hg commit -m "commit #3"

  $ hg up 2
  1 files updated, 0 files merged, 4 files removed, 0 files unresolved
  $ cat >> .hgignore << EOF
  > localignored
  > EOF
  $ hg add .hgignore
  $ hg commit -m "commit #4"

remote .hgignore shouldn't be used for determining whether a file is ignored
  $ echo This is file remoteignored4 > remoteignored
  $ hg merge 3 --config merge.checkignored=ignore --config merge.checkunknown=abort
  remoteignored: untracked file differs
  abort: untracked files in working directory differ from files in requested revision
  [255]
  $ hg merge 3 --config merge.checkignored=abort --config merge.checkunknown=ignore
  merging .hgignore
  merging for .hgignore
  3 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat remoteignored
  This is file remoteignored3
  $ cat remoteignored.orig
  This is file remoteignored4
  $ rm remoteignored.orig

local .hgignore should be used for that
  $ hg up --clean 4
  1 files updated, 0 files merged, 3 files removed, 0 files unresolved
  $ echo This is file localignored4 > localignored
also test other conflicting files to see we output the full set of warnings
  $ echo This is file b2 > b
  $ hg merge 3 --config merge.checkignored=abort --config merge.checkunknown=abort
  b: untracked file differs
  localignored: untracked file differs
  abort: untracked files in working directory differ from files in requested revision
  [255]
  $ hg merge 3 --config merge.checkignored=abort --config merge.checkunknown=ignore
  localignored: untracked file differs
  abort: untracked files in working directory differ from files in requested revision
  [255]
  $ hg merge 3 --config merge.checkignored=warn --config merge.checkunknown=abort
  b: untracked file differs
  abort: untracked files in working directory differ from files in requested revision
  [255]
  $ hg merge 3 --config merge.checkignored=warn --config merge.checkunknown=warn
  b: replacing untracked file
  localignored: replacing untracked file
  merging .hgignore
  merging for .hgignore
  3 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ cat localignored
  This is file localignored3
  $ cat localignored.orig
  This is file localignored4
  $ rm localignored.orig

  $ cat b.orig
  This is file b2
  $ hg up --clean 2
  0 files updated, 0 files merged, 4 files removed, 0 files unresolved
  $ mv b.orig b

this merge of b should work
  $ cat b
  This is file b2
  $ hg merge -f 1
  merging b
  merging for b
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg diff --nodates
  diff -r 49035e18a8e6 b
  --- /dev/null
  +++ b/b
  @@ -0,0 +1,1 @@
  +This is file b2
  $ hg status
  M b
  $ cd ..; rm -r t

  $ hg init t
  $ cd t
  $ echo This is file a1 > a
  $ hg add a
  $ hg commit -m "commit #0"
  $ echo This is file b1 > b
  $ hg add b
  $ hg commit -m "commit #1"
  $ echo This is file b22 > b
  $ hg commit -m "commit #2"
  $ hg update 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo This is file c1 > c
  $ hg add c
  $ hg commit -m "commit #3"
  created new head

Contents of b should be "this is file b1"
  $ cat b
  This is file b1

  $ echo This is file b22 > b
merge fails
  $ hg merge 2
  abort: uncommitted changes
  (use 'hg status' to list changes)
  [255]
merge expected!
  $ hg merge -f 2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg diff --nodates
  diff -r 85de557015a8 b
  --- a/b
  +++ b/b
  @@ -1,1 +1,1 @@
  -This is file b1
  +This is file b22
  $ hg status
  M b
  $ cd ..; rm -r t

  $ hg init t
  $ cd t
  $ echo This is file a1 > a
  $ hg add a
  $ hg commit -m "commit #0"
  $ echo This is file b1 > b
  $ hg add b
  $ hg commit -m "commit #1"
  $ echo This is file b22 > b
  $ hg commit -m "commit #2"
  $ hg update 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo This is file c1 > c
  $ hg add c
  $ hg commit -m "commit #3"
  created new head
  $ echo This is file b33 > b
merge of b should fail
  $ hg merge 2
  abort: uncommitted changes
  (use 'hg status' to list changes)
  [255]
merge of b expected
  $ hg merge -f 2
  merging b
  merging for b
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg diff --nodates
  diff -r 85de557015a8 b
  --- a/b
  +++ b/b
  @@ -1,1 +1,1 @@
  -This is file b1
  +This is file b33
  $ hg status
  M b

Test for issue2364

  $ hg up -qC .
  $ hg rm b
  $ hg ci -md
  $ hg revert -r -2 b
  $ hg up -q -- -2

Test that updated files are treated as "modified", when
'merge.update()' is aborted before 'merge.recordupdates()' (= parents
aren't changed), even if none of mode, size and timestamp of them
isn't changed on the filesystem (see also issue4583).

  $ cat > $TESTTMP/abort.py <<EOF
  > from __future__ import absolute_import
  > # emulate aborting before "recordupdates()". in this case, files
  > # are changed without updating dirstate
  > from mercurial import (
  >   error,
  >   extensions,
  >   merge,
  > )
  > def applyupdates(orig, *args, **kwargs):
  >     orig(*args, **kwargs)
  >     raise error.Abort('intentional aborting')
  > def extsetup(ui):
  >     extensions.wrapfunction(merge, "applyupdates", applyupdates)
  > EOF

  $ cat >> .hg/hgrc <<EOF
  > [fakedirstatewritetime]
  > # emulate invoking dirstate.write() via repo.status()
  > # at 2000-01-01 00:00
  > fakenow = 200001010000
  > EOF

(file gotten from other revision)

  $ hg update -q -C 2
  $ echo 'THIS IS FILE B5' > b
  $ hg commit -m 'commit #5'

  $ hg update -q -C 3
  $ cat b
  This is file b1
  $ touch -t 200001010000 b
  $ hg debugrebuildstate

  $ cat >> .hg/hgrc <<EOF
  > [extensions]
  > fakedirstatewritetime = $TESTDIR/fakedirstatewritetime.py
  > abort = $TESTTMP/abort.py
  > EOF
  $ hg merge 5
  abort: intentional aborting
  [255]
  $ cat >> .hg/hgrc <<EOF
  > [extensions]
  > fakedirstatewritetime = !
  > abort = !
  > EOF

  $ cat b
  THIS IS FILE B5
  $ touch -t 200001010000 b
  $ hg status -A b
  M b

(file merged from other revision)

  $ hg update -q -C 3
  $ echo 'this is file b6' > b
  $ hg commit -m 'commit #6'
  created new head

  $ cat b
  this is file b6
  $ touch -t 200001010000 b
  $ hg debugrebuildstate

  $ cat >> .hg/hgrc <<EOF
  > [extensions]
  > fakedirstatewritetime = $TESTDIR/fakedirstatewritetime.py
  > abort = $TESTTMP/abort.py
  > EOF
  $ hg merge --tool internal:other 5
  abort: intentional aborting
  [255]
  $ cat >> .hg/hgrc <<EOF
  > [extensions]
  > fakedirstatewritetime = !
  > abort = !
  > EOF

  $ cat b
  THIS IS FILE B5
  $ touch -t 200001010000 b
  $ hg status -A b
  M b

  $ cd ..