view tests/test-rebase-pull.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 >> $HGRCPATH <<EOF
  > [extensions]
  > rebase=
  > histedit=
  > 
  > [alias]
  > tglog = log -G --template "{rev}: {node|short} '{desc}' {branches}\n"
  > EOF


  $ hg init a
  $ cd a

  $ echo C1 > C1
  $ hg ci -Am C1
  adding C1

  $ echo C2 > C2
  $ hg ci -Am C2
  adding C2

  $ cd ..

  $ hg clone a b
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg clone a c
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ cd b

  $ echo L1 > L1
  $ hg ci -Am L1
  adding L1


  $ cd ../a

  $ echo R1 > R1
  $ hg ci -Am R1
  adding R1


  $ cd ../b

Now b has one revision to be pulled from a:

  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets 77ae9631bcca
  rebasing 2:ff8d69a621f9 "L1"
  saved backup bundle to $TESTTMP/b/.hg/strip-backup/ff8d69a621f9-160fa373-rebase.hg

  $ hg tglog
  @  3: d80cc2da061e 'L1'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
Re-run:

  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  no changes found

Abort pull early if working dir is not clean:

  $ echo L1-mod > L1
  $ hg pull --rebase
  abort: uncommitted changes
  (cannot pull with rebase: please commit or shelve your changes first)
  [255]
  $ hg update --clean --quiet

Abort pull early if another operation (histedit) is in progress:

  $ hg histedit . -q --commands - << EOF
  > edit d80cc2da061e histedit: generate unfinished state
  > EOF
  Editing (d80cc2da061e), you may commit or record as needed now.
  (hg histedit --continue to resume)
  [1]
  $ hg pull --rebase
  abort: histedit in progress
  (use 'hg histedit --continue' or 'hg histedit --abort')
  [255]
  $ hg histedit --abort --quiet

Abort pull early with pending uncommitted merge:

  $ cd ..
  $ hg clone --noupdate c d
  $ cd d
  $ hg tglog
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
  $ hg update --quiet 0
  $ echo M1 > M1
  $ hg commit --quiet -Am M1
  $ hg update --quiet 1
  $ hg merge 2
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg pull --rebase
  abort: outstanding uncommitted merge
  (cannot pull with rebase: please commit or shelve your changes first)
  [255]
  $ hg update --clean --quiet

Abort pull early with unclean subrepo:
  $ echo s = s > .hgsub
  $ hg add .hgsub
  $ hg init s
  $ hg commit -m "generated a subrepo"
  $ echo a > s/a
  $ hg -R s add s/a
  $ hg pull --rebase
  abort: uncommitted changes in subrepository "s"
  (cannot pull with rebase: please commit or shelve your changes first)
  [255]

Invoke pull --rebase and nothing to rebase:

  $ cd ../c

  $ hg book norebase
  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets 77ae9631bcca
  nothing to rebase - updating instead
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  updating bookmark norebase

  $ hg tglog -l 1
  @  2: 77ae9631bcca 'R1'
  |
  ~

pull --rebase --update should ignore --update:

  $ hg pull --rebase --update
  pulling from $TESTTMP/a
  searching for changes
  no changes found

pull --rebase doesn't update if nothing has been pulled:

  $ hg up -q 1

  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  no changes found

  $ hg tglog -l 1
  o  2: 77ae9631bcca 'R1'
  |
  ~

  $ cd ..

pull --rebase works when a specific revision is pulled (issue3619)

  $ cd a
  $ hg tglog
  @  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
  $ echo R2 > R2
  $ hg ci -Am R2
  adding R2
  $ echo R3 > R3
  $ hg ci -Am R3
  adding R3
  $ cd ../c
  $ hg tglog
  o  2: 77ae9631bcca 'R1'
  |
  @  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
  $ echo L1 > L1
  $ hg ci -Am L1
  adding L1
  created new head
  $ hg pull --rev tip --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 2 changes to 2 files
  new changesets 31cd3a05214e:770a61882ace
  rebasing 3:ff8d69a621f9 "L1"
  saved backup bundle to $TESTTMP/c/.hg/strip-backup/ff8d69a621f9-160fa373-rebase.hg
  $ hg tglog
  @  5: 518d153c0ba3 'L1'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
pull --rebase works with bundle2 turned on

  $ cd ../a
  $ echo R4 > R4
  $ hg ci -Am R4
  adding R4
  $ hg tglog
  @  5: 00e3b7781125 'R4'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
  $ cd ../c
  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets 00e3b7781125
  rebasing 5:518d153c0ba3 "L1"
  saved backup bundle to $TESTTMP/c/.hg/strip-backup/518d153c0ba3-73407f14-rebase.hg
  $ hg tglog
  @  6: 0d0727eb7ce0 'L1'
  |
  o  5: 00e3b7781125 'R4'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  

pull --rebase only update if there is nothing to rebase

  $ cd ../a
  $ echo R5 > R5
  $ hg ci -Am R5
  adding R5
  $ hg tglog
  @  6: 88dd24261747 'R5'
  |
  o  5: 00e3b7781125 'R4'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  
  $ cd ../c
  $ echo L2 > L2
  $ hg ci -Am L2
  adding L2
  $ hg up 'desc(L1)'
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets 88dd24261747
  rebasing 6:0d0727eb7ce0 "L1"
  rebasing 7:c1f58876e3bf "L2"
  saved backup bundle to $TESTTMP/c/.hg/strip-backup/0d0727eb7ce0-ef61ccb2-rebase.hg
  $ hg tglog
  o  8: 6dc0ea5dcf55 'L2'
  |
  @  7: 864e0a2d2614 'L1'
  |
  o  6: 88dd24261747 'R5'
  |
  o  5: 00e3b7781125 'R4'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  

pull --rebase update (no rebase) use proper update:

- warn about other head.

  $ cd ../a
  $ echo R6 > R6
  $ hg ci -Am R6
  adding R6
  $ cd ../c
  $ hg up 'desc(R5)'
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets 65bc164c1d9b
  nothing to rebase - updating instead
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  updated to "65bc164c1d9b: R6"
  1 other heads for branch "default"
  $ hg tglog
  @  9: 65bc164c1d9b 'R6'
  |
  | o  8: 6dc0ea5dcf55 'L2'
  | |
  | o  7: 864e0a2d2614 'L1'
  |/
  o  6: 88dd24261747 'R5'
  |
  o  5: 00e3b7781125 'R4'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'
  

Multiple pre-existing heads on the branch
-----------------------------------------

Pull bring content, but nothing on the current branch, we should not consider
pre-existing heads.

  $ cd ../a
  $ hg branch unrelatedbranch
  marked working directory as branch unrelatedbranch
  (branches are permanent and global, did you want a bookmark?)
  $ echo B1 > B1
  $ hg commit -Am B1
  adding B1
  $ cd ../c
  $ hg up 'desc(L2)'
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets 39c381359968
  nothing to rebase

There is two local heads and we pull a third one.
The second local head should not confuse the `hg pull rebase`.

  $ hg up 'desc(R6)'
  1 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ echo M1 > M1
  $ hg commit -Am M1
  adding M1
  $ cd ../a
  $ hg up 'desc(R6)'
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ echo R7 > R7
  $ hg commit -Am R7
  adding R7
  $ cd ../c
  $ hg up 'desc(L2)'
  2 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ hg pull --rebase
  pulling from $TESTTMP/a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files (+1 heads)
  new changesets f7d3e42052f9
  rebasing 7:864e0a2d2614 "L1"
  rebasing 8:6dc0ea5dcf55 "L2"
  saved backup bundle to $TESTTMP/c/.hg/strip-backup/864e0a2d2614-2f72c89c-rebase.hg
  $ hg tglog
  @  12: 3603a865eea0 'L2'
  |
  o  11: bcc8a9cd04bf 'L1'
  |
  o  10: f7d3e42052f9 'R7'
  |
  | o  9: 41fab4eef82f 'M1'
  |/
  | o  8: 39c381359968 'B1' unrelatedbranch
  |/
  o  7: 65bc164c1d9b 'R6'
  |
  o  6: 88dd24261747 'R5'
  |
  o  5: 00e3b7781125 'R4'
  |
  o  4: 770a61882ace 'R3'
  |
  o  3: 31cd3a05214e 'R2'
  |
  o  2: 77ae9631bcca 'R1'
  |
  o  1: 783333faa078 'C2'
  |
  o  0: 05d58a0c15dd 'C1'