streamclone: define first iteration of version 2 of stream format
(This patch is based on a first draft from Gregory Szorc, with deeper rework)
Version 1 of the stream clone format was invented many years ago and suffers
from a few deficiencies:
1) Filenames are stored in store-encoded (on filesystem) form rather than in
their internal form. This makes future compatibility with new store
filename encodings more difficult.
2) File entry "headers" consist of a newline of the file name followed by the
string file size. Converting strings to integers is avoidable overhead. We
can't store filenames with newlines (manifests have this limitation as
well, so it isn't a major concern). But the big concern here is the
necessity for readline(). Scanning for newlines means reading ahead and
that means extra buffer allocations and slicing (in Python) and this makes
performance suffer.
3) Filenames aren't compressed optimally. Filenames should be compressed well
since there is a lot of repeated data. However, since they are scattered
all over the stream (with revlog data in between), they typically fall
outside the window size of the compressor and don't compress.
4) It can only exchange stored based content, being able to exchange caches
too would be nice.
5) It is limited to a stream-based protocol and isn't suitable for an on-disk
format for general repository reading because the offset of individual file
entries requires scanning the entire file to find file records.
As part of enabling streaming clones to work in bundle2, #2 proved to have a
significant negative impact on performance. Since bundle2 provides the
opportunity to start fresh, Gregory Szorc figured he would take the
opportunity to invent a new streaming clone data format.
The new format devised in this series addresses #1, #2, and #4. It punts on #3
because it was complex without yielding a significant gain and on #5 because
devising a new store format that "packs" multiple revlogs into a single
"packed revlog" is massive scope bloat. However, this v2 format might be
suitable for streaming into a "packed revlog" with minimal processing. If it
works, great. If not, we can always invent stream format when it is needed.
This patch only introduces the bases of the format. We'll get it usable through
bundle2 first, then we'll extend the format in future patches to bring it to its
full potential (especially #4).
$ hg init test
$ cd test
$ echo 0 >> afile
$ hg add afile
$ hg commit -m "0.0"
$ echo 1 >> afile
$ hg commit -m "0.1"
$ echo 2 >> afile
$ hg commit -m "0.2"
$ echo 3 >> afile
$ hg commit -m "0.3"
$ hg update -C 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo 1 >> afile
$ hg commit -m "1.1"
created new head
$ echo 2 >> afile
$ hg commit -m "1.2"
$ echo a line > fred
$ echo 3 >> afile
$ hg add fred
$ hg commit -m "1.3"
$ hg mv afile adifferentfile
$ hg commit -m "1.3m"
$ hg update -C 3
1 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ hg mv afile anotherfile
$ hg commit -m "0.3m"
$ hg debugindex -f 1 afile
rev flag offset length size ..... link p1 p2 nodeid (re)
0 0000 0 3 2 ..... 0 -1 -1 362fef284ce2 (re)
1 0000 3 5 4 ..... 1 0 -1 125144f7e028 (re)
2 0000 8 7 6 ..... 2 1 -1 4c982badb186 (re)
3 0000 15 9 8 ..... 3 2 -1 19b1fc555737 (re)
$ hg debugindex adifferentfile
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 75 ..... 7 2565f3199a74 000000000000 000000000000 (re)
$ hg debugindex anotherfile
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 75 ..... 8 2565f3199a74 000000000000 000000000000 (re)
$ hg debugindex fred
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 8 ..... 6 12ab3bcc5ea4 000000000000 000000000000 (re)
$ hg debugindex --manifest
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 48 ..... 0 43eadb1d2d06 000000000000 000000000000 (re)
1 48 48 ..... 1 8b89697eba2c 43eadb1d2d06 000000000000 (re)
2 96 48 ..... 2 626a32663c2f 8b89697eba2c 000000000000 (re)
3 144 48 ..... 3 f54c32f13478 626a32663c2f 000000000000 (re)
4 192 .. ..... 6 de68e904d169 626a32663c2f 000000000000 (re)
5 2.. .. ..... 7 09bb521d218d de68e904d169 000000000000 (re)
6 3.. 54 ..... 8 1fde233dfb0f f54c32f13478 000000000000 (re)
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
4 files, 9 changesets, 7 total revisions
$ cd ..
$ for i in 0 1 2 3 4 5 6 7 8; do
> echo
> echo ---- hg clone -r "$i" test test-"$i"
> hg clone -r "$i" test test-"$i"
> cd test-"$i"
> hg verify
> cd ..
> done
---- hg clone -r 0 test test-0
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets f9ee2f85a263
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 1 changesets, 1 total revisions
---- hg clone -r 1 test test-1
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
new changesets f9ee2f85a263:34c2bf6b0626
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 2 changesets, 2 total revisions
---- hg clone -r 2 test test-2
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 1 files
new changesets f9ee2f85a263:e38ba6f5b7e0
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 3 changesets, 3 total revisions
---- hg clone -r 3 test test-3
adding changesets
adding manifests
adding file changes
added 4 changesets with 4 changes to 1 files
new changesets f9ee2f85a263:eebf5a27f8ca
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 4 changesets, 4 total revisions
---- hg clone -r 4 test test-4
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 1 files
new changesets f9ee2f85a263:095197eb4973
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 2 changesets, 2 total revisions
---- hg clone -r 5 test test-5
adding changesets
adding manifests
adding file changes
added 3 changesets with 3 changes to 1 files
new changesets f9ee2f85a263:1bb50a9436a7
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 3 changesets, 3 total revisions
---- hg clone -r 6 test test-6
adding changesets
adding manifests
adding file changes
added 4 changesets with 5 changes to 2 files
new changesets f9ee2f85a263:7373c1169842
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
2 files, 4 changesets, 5 total revisions
---- hg clone -r 7 test test-7
adding changesets
adding manifests
adding file changes
added 5 changesets with 6 changes to 3 files
new changesets f9ee2f85a263:a6a34bfa0076
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
3 files, 5 changesets, 6 total revisions
---- hg clone -r 8 test test-8
adding changesets
adding manifests
adding file changes
added 5 changesets with 5 changes to 2 files
new changesets f9ee2f85a263:aa35859c02ea
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
2 files, 5 changesets, 5 total revisions
$ cd test-8
$ hg pull ../test-7
pulling from ../test-7
searching for changes
adding changesets
adding manifests
adding file changes
added 4 changesets with 2 changes to 3 files (+1 heads)
new changesets 095197eb4973:a6a34bfa0076
(run 'hg heads' to see heads, 'hg merge' to merge)
$ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
4 files, 9 changesets, 7 total revisions
$ cd ..
$ hg clone test test-9
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd test-9
$ hg branch foobar
marked working directory as branch foobar
(branches are permanent and global, did you want a bookmark?)
$ echo file2 >> file2
$ hg add file2
$ hg commit -m "changeset9"
$ echo file3 >> file3
$ hg add file3
$ hg commit -m "changeset10"
$ cd ..
$ hg clone -r 9 -u foobar test-9 test-10
adding changesets
adding manifests
adding file changes
added 6 changesets with 6 changes to 3 files
new changesets f9ee2f85a263:7100abb79635
updating to branch foobar
2 files updated, 0 files merged, 0 files removed, 0 files unresolved