view tests/test-mq-guards.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

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=" >> $HGRCPATH

  $ hg init
  $ hg qinit

  $ echo x > x
  $ hg ci -Ama
  adding x

  $ hg qnew a.patch
  $ echo a > a
  $ hg add a
  $ hg qrefresh

  $ hg qnew b.patch
  $ echo b > b
  $ hg add b
  $ hg qrefresh

  $ hg qnew c.patch
  $ echo c > c
  $ hg add c
  $ hg qrefresh

  $ hg qpop -a
  popping c.patch
  popping b.patch
  popping a.patch
  patch queue now empty


should fail

  $ hg qguard does-not-exist.patch +bleh
  abort: no patch named does-not-exist.patch
  [255]


should fail

  $ hg qguard +fail
  abort: no patches applied
  [255]

  $ hg qpush
  applying a.patch
  now at: a.patch

should guard a.patch

  $ hg qguard +a

should print +a

  $ hg qguard
  a.patch: +a
  $ hg qpop
  popping a.patch
  patch queue now empty


should fail

  $ hg qpush a.patch
  cannot push 'a.patch' - guarded by '+a'
  [1]

  $ hg qguard a.patch
  a.patch: +a

should push b.patch

  $ hg qpush
  applying b.patch
  now at: b.patch

  $ hg qpop
  popping b.patch
  patch queue now empty

test selection of an empty guard

  $ hg qselect ""
  abort: guard cannot be an empty string
  [255]
  $ hg qselect a
  number of unguarded, unapplied patches has changed from 2 to 3

should push a.patch

  $ hg qpush
  applying a.patch
  now at: a.patch

  $ hg qguard -- c.patch -a

should print -a

  $ hg qguard c.patch
  c.patch: -a


should skip c.patch

  $ hg qpush -a
  applying b.patch
  skipping c.patch - guarded by '-a'
  now at: b.patch
  $ hg qnext
  all patches applied
  [1]

should display b.patch

  $ hg qtop
  b.patch

  $ hg qguard -n c.patch

should push c.patch

  $ hg qpush -a
  applying c.patch
  now at: c.patch

  $ hg qpop -a
  popping c.patch
  popping b.patch
  popping a.patch
  patch queue now empty
  $ hg qselect -n
  guards deactivated
  number of unguarded, unapplied patches has changed from 3 to 2

should push all

  $ hg qpush -a
  applying b.patch
  applying c.patch
  now at: c.patch

  $ hg qpop -a
  popping c.patch
  popping b.patch
  patch queue now empty
  $ hg qguard a.patch +1
  $ hg qguard b.patch +2
  $ hg qselect 1
  number of unguarded, unapplied patches has changed from 1 to 2

should push a.patch, not b.patch

  $ hg qpush
  applying a.patch
  now at: a.patch
  $ hg qpush
  applying c.patch
  now at: c.patch
  $ hg qpop -a
  popping c.patch
  popping a.patch
  patch queue now empty

  $ hg qselect 2

should push b.patch

  $ hg qpush
  applying b.patch
  now at: b.patch
  $ hg qpush -a
  applying c.patch
  now at: c.patch
  $ hg qprev
  b.patch

Used to be an issue with holes in the patch sequence
So, put one hole on the base and ask for topmost patch.

  $ hg qtop
  c.patch
  $ hg qpop -a
  popping c.patch
  popping b.patch
  patch queue now empty

  $ hg qselect 1 2
  number of unguarded, unapplied patches has changed from 2 to 3

should push a.patch, b.patch

  $ hg qpush
  applying a.patch
  now at: a.patch
  $ hg qpush
  applying b.patch
  now at: b.patch
  $ hg qpop -a
  popping b.patch
  popping a.patch
  patch queue now empty

  $ hg qguard -- a.patch +1 +2 -3
  $ hg qselect 1 2 3
  number of unguarded, unapplied patches has changed from 3 to 2


list patches and guards

  $ hg qguard -l
  a.patch: +1 +2 -3
  b.patch: +2
  c.patch: unguarded

have at least one patch applied to test coloring

  $ hg qpush
  applying b.patch
  now at: b.patch

list patches and guards with color

  $ hg --config extensions.color= qguard --config color.mode=ansi \
  >     -l --color=always
  \x1b[0;30;1ma.patch\x1b[0m: \x1b[0;33m+1\x1b[0m \x1b[0;33m+2\x1b[0m \x1b[0;31m-3\x1b[0m (esc)
  \x1b[0;34;1;4mb.patch\x1b[0m: \x1b[0;33m+2\x1b[0m (esc)
  \x1b[0;30;1mc.patch\x1b[0m: \x1b[0;32munguarded\x1b[0m (esc)

should pop b.patch

  $ hg qpop
  popping b.patch
  patch queue now empty

list series

  $ hg qseries -v
  0 G a.patch
  1 U b.patch
  2 U c.patch

list guards

  $ hg qselect
  1
  2
  3

should push b.patch

  $ hg qpush
  applying b.patch
  now at: b.patch

  $ hg qpush -a
  applying c.patch
  now at: c.patch
  $ hg qselect -n --reapply -v
  guards deactivated
  popping guarded patches
  popping c.patch
  popping b.patch
  patch queue now empty
  reapplying unguarded patches
  skipping a.patch - guarded by '+1' '+2'
  skipping b.patch - guarded by '+2'
  skipping a.patch - guarded by '+1' '+2'
  skipping b.patch - guarded by '+2'
  applying c.patch
  patching file c
  adding c
  committing files:
  c
  committing manifest
  committing changelog
  now at: c.patch

guards in series file: +1 +2 -3

  $ hg qselect -s
  +1
  +2
  -3

should show c.patch

  $ hg qapplied
  c.patch

  $ hg qrename a.patch new.patch

should show :


new.patch: +1 +2 -3


b.patch: +2


c.patch: unguarded

  $ hg qguard -l
  new.patch: +1 +2 -3
  b.patch: +2
  c.patch: unguarded

  $ hg qnew d.patch
  $ hg qpop
  popping d.patch
  now at: c.patch

should show new.patch and b.patch as Guarded, c.patch as Applied


and d.patch as Unapplied

  $ hg qseries -v
  0 G new.patch
  1 G b.patch
  2 A c.patch
  3 U d.patch

qseries again, but with color

  $ hg --config extensions.color= --config color.mode=ansi qseries -v --color=always
  0 G \x1b[0;30;1mnew.patch\x1b[0m (esc)
  1 G \x1b[0;30;1mb.patch\x1b[0m (esc)
  2 A \x1b[0;34;1;4mc.patch\x1b[0m (esc)
  3 U \x1b[0;30;1md.patch\x1b[0m (esc)

  $ hg qguard d.patch +2

new.patch, b.patch: Guarded. c.patch: Applied. d.patch: Guarded.

  $ hg qseries -v
  0 G new.patch
  1 G b.patch
  2 A c.patch
  3 G d.patch

  $ qappunappv()
  > {
  >     for command in qapplied "qapplied -v" qunapplied "qunapplied -v"; do
  >         echo % hg $command
  >         hg $command
  >     done
  > }

  $ hg qpop -a
  popping c.patch
  patch queue now empty
  $ hg qguard -l
  new.patch: +1 +2 -3
  b.patch: +2
  c.patch: unguarded
  d.patch: +2
  $ qappunappv
  % hg qapplied
  % hg qapplied -v
  % hg qunapplied
  c.patch
  % hg qunapplied -v
  0 G new.patch
  1 G b.patch
  2 U c.patch
  3 G d.patch
  $ hg qselect 1
  number of unguarded, unapplied patches has changed from 1 to 2
  $ qappunappv
  % hg qapplied
  % hg qapplied -v
  % hg qunapplied
  new.patch
  c.patch
  % hg qunapplied -v
  0 U new.patch
  1 G b.patch
  2 U c.patch
  3 G d.patch
  $ hg qpush -a
  applying new.patch
  skipping b.patch - guarded by '+2'
  applying c.patch
  skipping d.patch - guarded by '+2'
  now at: c.patch
  $ qappunappv
  % hg qapplied
  new.patch
  c.patch
  % hg qapplied -v
  0 A new.patch
  1 G b.patch
  2 A c.patch
  % hg qunapplied
  % hg qunapplied -v
  3 G d.patch
  $ hg qselect 2
  number of unguarded, unapplied patches has changed from 0 to 1
  $ qappunappv
  % hg qapplied
  new.patch
  c.patch
  % hg qapplied -v
  0 A new.patch
  1 U b.patch
  2 A c.patch
  % hg qunapplied
  d.patch
  % hg qunapplied -v
  3 U d.patch

  $ for patch in `hg qseries`; do
  >     echo % hg qapplied $patch
  >     hg qapplied $patch
  >     echo % hg qunapplied $patch
  >     hg qunapplied $patch
  > done
  % hg qapplied new.patch
  new.patch
  % hg qunapplied new.patch
  b.patch
  d.patch
  % hg qapplied b.patch
  new.patch
  % hg qunapplied b.patch
  d.patch
  % hg qapplied c.patch
  new.patch
  c.patch
  % hg qunapplied c.patch
  d.patch
  % hg qapplied d.patch
  new.patch
  c.patch
  % hg qunapplied d.patch


hg qseries -m: only b.patch should be shown
the guards file was not ignored in the past

  $ hg qdelete -k b.patch
  $ hg qseries -m
  b.patch

hg qseries -m with color

  $ hg --config extensions.color= --config color.mode=ansi qseries -m --color=always
  \x1b[0;31;1mb.patch\x1b[0m (esc)


excercise corner cases in "qselect --reapply"

  $ hg qpop -a
  popping c.patch
  popping new.patch
  patch queue now empty
  $ hg qguard -- new.patch -not-new
  $ hg qguard -- c.patch -not-c
  $ hg qguard -- d.patch -not-d
  $ hg qpush -a
  applying new.patch
  applying c.patch
  applying d.patch
  patch d.patch is empty
  now at: d.patch
  $ hg qguard -l
  new.patch: -not-new
  c.patch: -not-c
  d.patch: -not-d
  $ hg qselect --reapply not-d
  popping guarded patches
  popping d.patch
  now at: c.patch
  reapplying unguarded patches
  cannot push 'd.patch' - guarded by '-not-d'
  $ hg qser -v
  0 A new.patch
  1 A c.patch
  2 G d.patch
  $ hg qselect --reapply -n
  guards deactivated
  $ hg qpush
  applying d.patch
  patch d.patch is empty
  now at: d.patch
  $ hg qser -v
  0 A new.patch
  1 A c.patch
  2 A d.patch
  $ hg qselect --reapply not-c
  popping guarded patches
  popping d.patch
  popping c.patch
  now at: new.patch
  reapplying unguarded patches
  applying d.patch
  patch d.patch is empty
  now at: d.patch
  $ hg qser -v
  0 A new.patch
  1 G c.patch
  2 A d.patch
  $ hg qselect --reapply not-new
  popping guarded patches
  popping d.patch
  popping new.patch
  patch queue now empty
  reapplying unguarded patches
  applying c.patch
  applying d.patch
  patch d.patch is empty
  now at: d.patch
  $ hg qser -v
  0 G new.patch
  1 A c.patch
  2 A d.patch

test that qselect shows "number of guarded, applied patches" correctly

  $ hg qimport -q -e b.patch
  adding b.patch to series file
  $ hg qguard -- b.patch -not-b
  $ hg qpop -a -q
  patch queue now empty
  $ hg qunapplied -v
  0 G new.patch
  1 U c.patch
  2 U d.patch
  3 U b.patch
  $ hg qselect not-new not-c
  number of unguarded, unapplied patches has changed from 3 to 2
  $ hg qpush -q -a
  patch d.patch is empty
  now at: b.patch

  $ hg qapplied -v
  0 G new.patch
  1 G c.patch
  2 A d.patch
  3 A b.patch
  $ hg qselect --none
  guards deactivated
  $ hg qselect not-new not-c not-d
  number of guarded, applied patches has changed from 0 to 1

test that "qselect --reapply" reapplies patches successfully when the
already applied patch becomes unguarded and it follows the already
guarded (= not yet applied) one.

  $ hg qpop -q -a
  patch queue now empty
  $ hg qselect not-new not-c
  number of unguarded, unapplied patches has changed from 1 to 2
  $ hg qpush -q -a
  patch d.patch is empty
  now at: b.patch
  $ hg qapplied -v
  0 G new.patch
  1 G c.patch
  2 A d.patch
  3 A b.patch
  $ hg qselect -q --reapply not-c not-b
  now at: d.patch
  cannot push 'b.patch' - guarded by '-not-b'
  $ hg qseries -v
  0 U new.patch
  1 G c.patch
  2 A d.patch
  3 G b.patch

test that "qselect --reapply" checks applied patches correctly when no
applied patches becomes guarded but some of unapplied ones become
unguarded.

  $ hg qpop -q -a
  patch queue now empty
  $ hg qselect not-new not-c not-d
  number of unguarded, unapplied patches has changed from 2 to 1
  $ hg qpush -q -a
  now at: b.patch
  $ hg qapplied -v
  0 G new.patch
  1 G c.patch
  2 G d.patch
  3 A b.patch
  $ hg qselect -q --reapply not-new not-c
  $ hg qseries -v
  0 G new.patch
  1 G c.patch
  2 U d.patch
  3 A b.patch