Mercurial > hg
annotate tests/test-clone-pull-corruption.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
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Tue, 09 Oct 2018 08:50:13 -0700 |
parents | f1186c292d03 |
children | 2f2682f40ea0 |
rev | line source |
---|---|
12412
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
1 Corrupt an hg repo with a pull started during an aborted commit |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
2 Create two repos, so that one of them can pull from the other one. |
1785
81ca1a9bd061
Added test cases for repo corruption fixed in 2e0a288ca93e (issue132)
Thomas Arendsen Hein <thomas@intevation.de>
parents:
diff
changeset
|
3 |
12412
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
4 $ hg init source |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
5 $ cd source |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
6 $ touch foo |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
7 $ hg add foo |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
8 $ hg ci -m 'add foo' |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
9 $ hg clone . ../corrupted |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
10 updating to branch default |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
11 1 files updated, 0 files merged, 0 files removed, 0 files unresolved |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
12 $ echo >> foo |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
13 $ hg ci -m 'change foo' |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
14 |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
15 Add a hook to wait 5 seconds and then abort the commit |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
16 |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
17 $ cd ../corrupted |
16962
d2fe9aaedcaf
test-clone-pull-corruption: adapt for Windows
Adrian Buehlmann <adrian@cadifra.com>
parents:
16913
diff
changeset
|
18 $ echo "[hooks]" >> .hg/hgrc |
24838
b2c1ff96c1e1
tests: use double quote to quote arguments in hook for portability
FUJIWARA Katsunori <foozy@lares.dti.ne.jp>
parents:
16962
diff
changeset
|
19 $ echo 'pretxncommit = sh -c "sleep 5; exit 1"' >> .hg/hgrc |
12412
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
20 |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
21 start a commit... |
1785
81ca1a9bd061
Added test cases for repo corruption fixed in 2e0a288ca93e (issue132)
Thomas Arendsen Hein <thomas@intevation.de>
parents:
diff
changeset
|
22 |
12412
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
23 $ touch bar |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
24 $ hg add bar |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
25 $ hg ci -m 'add bar' & |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
26 |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
27 ... and start a pull while the commit is still running |
1785
81ca1a9bd061
Added test cases for repo corruption fixed in 2e0a288ca93e (issue132)
Thomas Arendsen Hein <thomas@intevation.de>
parents:
diff
changeset
|
28 |
12412
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
29 $ sleep 1 |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
30 $ hg pull ../source 2>/dev/null |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
31 pulling from ../source |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
32 transaction abort! |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
33 rollback completed |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
34 abort: pretxncommit hook exited with status 1 |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
35 searching for changes |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
36 adding changesets |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
37 adding manifests |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
38 adding file changes |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
39 added 1 changesets with 1 changes to 1 files |
34661
eb586ed5d8ce
transaction-summary: show the range of new revisions upon pull/unbundle (BC)
Denis Laxalde <denis.laxalde@logilab.fr>
parents:
24838
diff
changeset
|
40 new changesets 52998019f625 |
12412
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
41 (run 'hg update' to get a working copy) |
1785
81ca1a9bd061
Added test cases for repo corruption fixed in 2e0a288ca93e (issue132)
Thomas Arendsen Hein <thomas@intevation.de>
parents:
diff
changeset
|
42 |
12412
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
43 see what happened |
1785
81ca1a9bd061
Added test cases for repo corruption fixed in 2e0a288ca93e (issue132)
Thomas Arendsen Hein <thomas@intevation.de>
parents:
diff
changeset
|
44 |
12412
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
45 $ wait |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
46 $ hg verify |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
47 checking changesets |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
48 checking manifests |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
49 crosschecking files in changesets and manifests |
2dbb9e5e3454
tests: unify test-clone-pull-corruption
Matt Mackall <mpm@selenic.com>
parents:
1785
diff
changeset
|
50 checking files |
39489
f1186c292d03
verify: make output less confusing (issue5924)
Meirambek Omyrzak <meirambek77@gmail.com>
parents:
34661
diff
changeset
|
51 checked 2 changesets with 2 changes to 1 files |
16913
f2719b387380
tests: add missing trailing 'cd ..'
Mads Kiilerich <mads@kiilerich.com>
parents:
15445
diff
changeset
|
52 |
f2719b387380
tests: add missing trailing 'cd ..'
Mads Kiilerich <mads@kiilerich.com>
parents:
15445
diff
changeset
|
53 $ cd .. |