view tests/test-mq-qrefresh-interactive.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

Create configuration

  $ echo "[ui]" >> $HGRCPATH
  $ echo "interactive=true" >> $HGRCPATH

help qrefresh (no record)

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=" >> $HGRCPATH
  $ hg help qrefresh
  hg qrefresh [-I] [-X] [-e] [-m TEXT] [-l FILE] [-s] [FILE]...
  
  update the current patch
  
      If any file patterns are provided, the refreshed patch will contain only
      the modifications that match those patterns; the remaining modifications
      will remain in the working directory.
  
      If -s/--short is specified, files currently included in the patch will be
      refreshed just like matched files and remain in the patch.
  
      If -e/--edit is specified, Mercurial will start your configured editor for
      you to enter a message. In case qrefresh fails, you will find a backup of
      your message in ".hg/last-message.txt".
  
      hg add/remove/copy/rename work as usual, though you might want to use git-
      style patches (-g/--git or [diff] git=1) to track copies and renames. See
      the diffs help topic for more information on the git diff format.
  
      Returns 0 on success.
  
  options ([+] can be repeated):
  
   -e --edit                invoke editor on commit messages
   -g --git                 use git extended diff format
   -s --short               refresh only files already in the patch and
                            specified files
   -U --currentuser         add/update author field in patch with current user
   -u --user USER           add/update author field in patch with given user
   -D --currentdate         add/update date field in patch with current date
   -d --date DATE           add/update date field in patch with given date
   -I --include PATTERN [+] include names matching the given patterns
   -X --exclude PATTERN [+] exclude names matching the given patterns
   -m --message TEXT        use text as commit message
   -l --logfile FILE        read commit message from file
  
  (some details hidden, use --verbose to show complete help)

help qrefresh (record)

  $ echo "record=" >> $HGRCPATH
  $ hg help qrefresh
  hg qrefresh [-I] [-X] [-e] [-m TEXT] [-l FILE] [-s] [FILE]...
  
  update the current patch
  
      If any file patterns are provided, the refreshed patch will contain only
      the modifications that match those patterns; the remaining modifications
      will remain in the working directory.
  
      If -s/--short is specified, files currently included in the patch will be
      refreshed just like matched files and remain in the patch.
  
      If -e/--edit is specified, Mercurial will start your configured editor for
      you to enter a message. In case qrefresh fails, you will find a backup of
      your message in ".hg/last-message.txt".
  
      hg add/remove/copy/rename work as usual, though you might want to use git-
      style patches (-g/--git or [diff] git=1) to track copies and renames. See
      the diffs help topic for more information on the git diff format.
  
      Returns 0 on success.
  
  options ([+] can be repeated):
  
   -e --edit                invoke editor on commit messages
   -g --git                 use git extended diff format
   -s --short               refresh only files already in the patch and
                            specified files
   -U --currentuser         add/update author field in patch with current user
   -u --user USER           add/update author field in patch with given user
   -D --currentdate         add/update date field in patch with current date
   -d --date DATE           add/update date field in patch with given date
   -I --include PATTERN [+] include names matching the given patterns
   -X --exclude PATTERN [+] exclude names matching the given patterns
   -m --message TEXT        use text as commit message
   -l --logfile FILE        read commit message from file
   -i --interactive         interactively select changes to refresh
  
  (some details hidden, use --verbose to show complete help)

  $ hg init a
  $ cd a

Base commit

  $ cat > 1.txt <<EOF
  > 1
  > 2
  > 3
  > 4
  > 5
  > EOF
  $ cat > 2.txt <<EOF
  > a
  > b
  > c
  > d
  > e
  > f
  > EOF

  $ mkdir dir
  $ cat > dir/a.txt <<EOF
  > hello world
  > 
  > someone
  > up
  > there
  > loves
  > me
  > EOF

  $ hg add 1.txt 2.txt dir/a.txt
  $ hg commit -m aaa
  $ hg qrecord --config ui.interactive=false patch
  abort: running non-interactively, use qnew instead
  [255]
  $ hg qnew -i --config ui.interactive=false patch
  abort: running non-interactively
  [255]
  $ hg qnew -d '0 0' patch

Changing files

  $ sed -e 's/2/2 2/;s/4/4 4/' 1.txt > 1.txt.new
  $ sed -e 's/b/b b/' 2.txt > 2.txt.new
  $ sed -e 's/hello world/hello world!/' dir/a.txt > dir/a.txt.new

  $ mv -f 1.txt.new 1.txt
  $ mv -f 2.txt.new 2.txt
  $ mv -f dir/a.txt.new dir/a.txt

Whole diff

  $ hg diff --nodates
  diff -r ed27675cb5df 1.txt
  --- a/1.txt
  +++ b/1.txt
  @@ -1,5 +1,5 @@
   1
  -2
  +2 2
   3
  -4
  +4 4
   5
  diff -r ed27675cb5df 2.txt
  --- a/2.txt
  +++ b/2.txt
  @@ -1,5 +1,5 @@
   a
  -b
  +b b
   c
   d
   e
  diff -r ed27675cb5df dir/a.txt
  --- a/dir/a.txt
  +++ b/dir/a.txt
  @@ -1,4 +1,4 @@
  -hello world
  +hello world!
   
   someone
   up

partial qrefresh

  $ hg qrefresh -i --config ui.interactive=false
  abort: running non-interactively
  [255]
  $ hg qrefresh -i -d '0 0' <<EOF
  > y
  > y
  > n
  > y
  > y
  > n
  > EOF
  diff --git a/1.txt b/1.txt
  2 hunks, 2 lines changed
  examine changes to '1.txt'? [Ynesfdaq?] y
  
  @@ -1,3 +1,3 @@
   1
  -2
  +2 2
   3
  record change 1/4 to '1.txt'? [Ynesfdaq?] y
  
  @@ -3,3 +3,3 @@
   3
  -4
  +4 4
   5
  record change 2/4 to '1.txt'? [Ynesfdaq?] n
  
  diff --git a/2.txt b/2.txt
  1 hunks, 1 lines changed
  examine changes to '2.txt'? [Ynesfdaq?] y
  
  @@ -1,5 +1,5 @@
   a
  -b
  +b b
   c
   d
   e
  record change 3/4 to '2.txt'? [Ynesfdaq?] y
  
  diff --git a/dir/a.txt b/dir/a.txt
  1 hunks, 1 lines changed
  examine changes to 'dir/a.txt'? [Ynesfdaq?] n
  

After partial qrefresh 'tip'

  $ hg tip -p
  changeset:   1:0738af1a8211
  tag:         patch
  tag:         qbase
  tag:         qtip
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     [mq]: patch
  
  diff -r 1fd39ab63a33 -r 0738af1a8211 1.txt
  --- a/1.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/1.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,5 +1,5 @@
   1
  -2
  +2 2
   3
   4
   5
  diff -r 1fd39ab63a33 -r 0738af1a8211 2.txt
  --- a/2.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/2.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,5 +1,5 @@
   a
  -b
  +b b
   c
   d
   e
  
After partial qrefresh 'diff'

  $ hg diff --nodates
  diff -r 0738af1a8211 1.txt
  --- a/1.txt
  +++ b/1.txt
  @@ -1,5 +1,5 @@
   1
   2 2
   3
  -4
  +4 4
   5
  diff -r 0738af1a8211 dir/a.txt
  --- a/dir/a.txt
  +++ b/dir/a.txt
  @@ -1,4 +1,4 @@
  -hello world
  +hello world!
   
   someone
   up

qrefresh interactively everything else

  $ hg qrefresh -i -d '0 0' <<EOF
  > y
  > y
  > y
  > y
  > EOF
  diff --git a/1.txt b/1.txt
  1 hunks, 1 lines changed
  examine changes to '1.txt'? [Ynesfdaq?] y
  
  @@ -1,5 +1,5 @@
   1
   2 2
   3
  -4
  +4 4
   5
  record change 1/2 to '1.txt'? [Ynesfdaq?] y
  
  diff --git a/dir/a.txt b/dir/a.txt
  1 hunks, 1 lines changed
  examine changes to 'dir/a.txt'? [Ynesfdaq?] y
  
  @@ -1,4 +1,4 @@
  -hello world
  +hello world!
   
   someone
   up
  record change 2/2 to 'dir/a.txt'? [Ynesfdaq?] y
  

After final qrefresh 'tip'

  $ hg tip -p
  changeset:   1:2c3f66afeed9
  tag:         patch
  tag:         qbase
  tag:         qtip
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     [mq]: patch
  
  diff -r 1fd39ab63a33 -r 2c3f66afeed9 1.txt
  --- a/1.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/1.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,5 +1,5 @@
   1
  -2
  +2 2
   3
  -4
  +4 4
   5
  diff -r 1fd39ab63a33 -r 2c3f66afeed9 2.txt
  --- a/2.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/2.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,5 +1,5 @@
   a
  -b
  +b b
   c
   d
   e
  diff -r 1fd39ab63a33 -r 2c3f66afeed9 dir/a.txt
  --- a/dir/a.txt	Thu Jan 01 00:00:00 1970 +0000
  +++ b/dir/a.txt	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,4 +1,4 @@
  -hello world
  +hello world!
   
   someone
   up
  

After qrefresh 'diff'

  $ hg diff --nodates

  $ cd ..