view tests/test-narrow.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

#testcases flat tree

  $ . "$TESTDIR/narrow-library.sh"

#if tree
  $ cat << EOF >> $HGRCPATH
  > [experimental]
  > treemanifest = 1
  > EOF
#endif

  $ hg init master
  $ cd master
  $ cat >> .hg/hgrc <<EOF
  > [narrow]
  > serveellipses=True
  > EOF
  $ for x in `$TESTDIR/seq.py 0 10`
  > do
  >   mkdir d$x
  >   echo $x > d$x/f
  >   hg add d$x/f
  >   hg commit -m "add d$x/f"
  > done
  $ hg log -T "{rev}: {desc}\n"
  10: add d10/f
  9: add d9/f
  8: add d8/f
  7: add d7/f
  6: add d6/f
  5: add d5/f
  4: add d4/f
  3: add d3/f
  2: add d2/f
  1: add d1/f
  0: add d0/f
  $ cd ..

Error if '.' or '..' are in the directory to track.
  $ hg clone --narrow ssh://user@dummy/master foo --include ./asdf
  abort: "." and ".." are not allowed in narrowspec paths
  [255]
  $ hg clone --narrow ssh://user@dummy/master foo --include asdf/..
  abort: "." and ".." are not allowed in narrowspec paths
  [255]
  $ hg clone --narrow ssh://user@dummy/master foo --include a/./c
  abort: "." and ".." are not allowed in narrowspec paths
  [255]

Names with '.' in them are OK.
  $ hg clone --narrow ssh://user@dummy/master should-work --include a/.b/c
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files
  new changesets * (glob)
  updating to branch default
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved

Test repo with local changes
  $ hg clone --narrow ssh://user@dummy/master narrow-local-changes --include d0 --include d3 --include d6
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 6 changesets with 3 changes to 3 files
  new changesets *:* (glob)
  updating to branch default
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd narrow-local-changes
  $ cat >> $HGRCPATH << EOF
  > [experimental]
  > evolution=createmarkers
  > EOF
  $ echo local change >> d0/f
  $ hg ci -m 'local change to d0'
  $ hg co '.^'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo local change >> d3/f
  $ hg ci -m 'local hidden change to d3'
  created new head
  $ hg ci --amend -m 'local change to d3'
  $ hg tracked --removeinclude d0
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  The following changeset(s) or their ancestors have local changes not on the remote:
  * (glob)
  abort: local changes found
  (use --force-delete-local-changes to ignore)
  [255]
Check that nothing was removed by the failed attempts
  $ hg tracked
  I path:d0
  I path:d3
  I path:d6
  $ hg files
  d0/f
  d3/f
  d6/f
  $ find *
  d0
  d0/f
  d3
  d3/f
  d6
  d6/f
  $ hg verify -q
Force deletion of local changes
  $ hg log -T "{rev}: {desc} {outsidenarrow}\n"
  8: local change to d3 
  6: local change to d0 
  5: add d10/f outsidenarrow
  4: add d6/f 
  3: add d5/f outsidenarrow
  2: add d3/f 
  1: add d2/f outsidenarrow
  0: add d0/f 
  $ hg tracked --removeinclude d0 --force-delete-local-changes
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  The following changeset(s) or their ancestors have local changes not on the remote:
  * (glob)
  saved backup bundle to $TESTTMP/narrow-local-changes/.hg/strip-backup/*-narrow.hg (glob)
  deleting data/d0/f.i (reporevlogstore !)
  deleting meta/d0/00manifest.i (tree !)
  deleting data/d0/f/362fef284ce2ca02aecc8de6d5e8a1c3af0556fe (reposimplestore !)
  deleting data/d0/f/4374b5650fc5ae54ac857c0f0381971fdde376f7 (reposimplestore !)
  deleting data/d0/f/index (reposimplestore !)

  $ hg log -T "{rev}: {desc} {outsidenarrow}\n"
  7: local change to d3 
  5: add d10/f outsidenarrow
  4: add d6/f 
  3: add d5/f outsidenarrow
  2: add d3/f 
  1: add d2/f outsidenarrow
  0: add d0/f outsidenarrow
Can restore stripped local changes after widening
  $ hg tracked --addinclude d0 -q
  $ hg unbundle .hg/strip-backup/*-narrow.hg -q
  $ hg --hidden co -r 'desc("local change to d0")' -q
  $ cat d0/f
  0
  local change
Pruned commits affecting removed paths should not prevent narrowing
  $ hg co '.^'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg debugobsolete `hg log -T '{node}' -r 'desc("local change to d0")'`
  obsoleted 1 changesets
  $ hg tracked --removeinclude d0
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  saved backup bundle to $TESTTMP/narrow-local-changes/.hg/strip-backup/*-narrow.hg (glob)
  deleting data/d0/f.i (reporevlogstore !)
  deleting meta/d0/00manifest.i (tree !)
  deleting data/d0/f/362fef284ce2ca02aecc8de6d5e8a1c3af0556fe (reposimplestore !)
  deleting data/d0/f/4374b5650fc5ae54ac857c0f0381971fdde376f7 (reposimplestore !)
  deleting data/d0/f/index (reposimplestore !)

Updates off of stripped commit if necessary
  $ hg co -r 'desc("local change to d3")' -q
  $ echo local change >> d6/f
  $ hg ci -m 'local change to d6'
  $ hg tracked --removeinclude d3 --force-delete-local-changes
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  The following changeset(s) or their ancestors have local changes not on the remote:
  * (glob)
  * (glob)
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/narrow-local-changes/.hg/strip-backup/*-narrow.hg (glob)
  deleting data/d3/f.i (reporevlogstore !)
  deleting meta/d3/00manifest.i (tree !)
  deleting data/d3/f/2661d26c649684b482d10f91960cc3db683c38b4 (reposimplestore !)
  deleting data/d3/f/99fa7136105a15e2045ce3d9152e4837c5349e4d (reposimplestore !)
  deleting data/d3/f/index (reposimplestore !)
  $ hg log -T '{desc}\n' -r .
  add d10/f
Updates to nullid if necessary
  $ hg tracked --addinclude d3 -q
  $ hg co null -q
  $ mkdir d3
  $ echo local change > d3/f
  $ hg add d3/f
  $ hg ci -m 'local change to d3'
  created new head
  $ hg tracked --removeinclude d3 --force-delete-local-changes
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  The following changeset(s) or their ancestors have local changes not on the remote:
  * (glob)
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/narrow-local-changes/.hg/strip-backup/*-narrow.hg (glob)
  deleting data/d3/f.i (reporevlogstore !)
  deleting meta/d3/00manifest.i (tree !)
  deleting data/d3/f/2661d26c649684b482d10f91960cc3db683c38b4 (reposimplestore !)
  deleting data/d3/f/5ce0767945cbdbca3b924bb9fbf5143f72ab40ac (reposimplestore !)
  deleting data/d3/f/index (reposimplestore !)
  $ hg id
  000000000000
  $ cd ..

Can remove last include, making repo empty
  $ hg clone --narrow ssh://user@dummy/master narrow-empty --include d0 -r 5
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 1 changes to 1 files
  new changesets *:* (glob)
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd narrow-empty
  $ hg tracked --removeinclude d0
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  deleting data/d0/f.i (reporevlogstore !)
  deleting meta/d0/00manifest.i (tree !)
  deleting data/d0/f/362fef284ce2ca02aecc8de6d5e8a1c3af0556fe (reposimplestore !)
  deleting data/d0/f/index (reposimplestore !)
  $ hg tracked
  $ hg files
  [1]
  $ test -d d0
  [1]
Do some work in the empty clone
  $ hg diff --change .
  $ hg branch foo
  marked working directory as branch foo
  (branches are permanent and global, did you want a bookmark?)
  $ hg ci -m empty
  $ hg pull -q
Can widen the empty clone
  $ hg tracked --addinclude d0
  comparing with ssh://user@dummy/master
  searching for changes
  no changes found
  saved backup bundle to $TESTTMP/narrow-empty/.hg/strip-backup/*-widen.hg (glob)
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 1 changes to 1 files
  new changesets *:* (glob)
  $ hg tracked
  I path:d0
  $ hg files
  d0/f
  $ find *
  d0
  d0/f
  $ cd ..

TODO(martinvonz): test including e.g. d3/g and then removing it once
https://bitbucket.org/Google/narrowhg/issues/6 is fixed

  $ hg clone --narrow ssh://user@dummy/master narrow --include d0 --include d3 --include d6 --include d9
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 8 changesets with 4 changes to 4 files
  new changesets *:* (glob)
  updating to branch default
  4 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd narrow
  $ hg tracked
  I path:d0
  I path:d3
  I path:d6
  I path:d9
  $ hg tracked --removeinclude d6
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  deleting data/d6/f.i (reporevlogstore !)
  deleting meta/d6/00manifest.i (tree !)
  deleting data/d6/f/7339d30678f451ac8c3f38753beeb4cf2e1655c7 (reposimplestore !)
  deleting data/d6/f/index (reposimplestore !)
  $ hg tracked
  I path:d0
  I path:d3
  I path:d9
#if repofncache
  $ hg debugrebuildfncache
  fncache already up to date
#endif
  $ find *
  d0
  d0/f
  d3
  d3/f
  d9
  d9/f
  $ hg verify -q
  $ hg tracked --addexclude d3/f
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  deleting data/d3/f.i (reporevlogstore !)
  deleting data/d3/f/2661d26c649684b482d10f91960cc3db683c38b4 (reposimplestore !)
  deleting data/d3/f/index (reposimplestore !)
  $ hg tracked
  I path:d0
  I path:d3
  I path:d9
  X path:d3/f
#if repofncache
  $ hg debugrebuildfncache
  fncache already up to date
#endif
  $ find *
  d0
  d0/f
  d9
  d9/f
  $ hg verify -q
  $ hg tracked --addexclude d0
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  deleting data/d0/f.i (reporevlogstore !)
  deleting meta/d0/00manifest.i (tree !)
  deleting data/d0/f/362fef284ce2ca02aecc8de6d5e8a1c3af0556fe (reposimplestore !)
  deleting data/d0/f/index (reposimplestore !)
  $ hg tracked
  I path:d3
  I path:d9
  X path:d0
  X path:d3/f
#if repofncache
  $ hg debugrebuildfncache
  fncache already up to date
#endif
  $ find *
  d9
  d9/f

Make a 15 of changes to d9 to test the path without --verbose
(Note: using regexes instead of "* (glob)" because if the test fails, it
produces more sensible diffs)
  $ hg tracked
  I path:d3
  I path:d9
  X path:d0
  X path:d3/f
  $ for x in `$TESTDIR/seq.py 1 15`
  > do
  >   echo local change >> d9/f
  >   hg commit -m "change $x to d9/f"
  > done
  $ hg tracked --removeinclude d9
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  The following changeset(s) or their ancestors have local changes not on the remote:
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ...and 5 more, use --verbose to list all
  abort: local changes found
  (use --force-delete-local-changes to ignore)
  [255]
Now test it *with* verbose.
  $ hg tracked --removeinclude d9 --verbose
  comparing with ssh://user@dummy/master
  searching for changes
  looking for local changes to affected paths
  The following changeset(s) or their ancestors have local changes not on the remote:
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  ^[0-9a-f]{12}$ (re)
  abort: local changes found
  (use --force-delete-local-changes to ignore)
  [255]