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  1. Oct 17, 2018
    • Gregory Szorc's avatar
      exchangev2: support for calling rawstorefiledata to retrieve raw files · 00a4cd36
      Gregory Szorc authored
      This is somewhat hacky. For that I apologize.
      
      At the 4.8 Sprint, we decided we wanted to land support in wireprotov2 for doing
      a partial clone with changelog and manifestlog bootstrapped from a "stream clone"
      like primitive.
      
      This commit implements the client-side bits necessary to facilitate that.
      
      If the new server-side command for obtaining raw files data is available, we
      call it to get the raw files for the changelog and manifestlog. Then we
      fall through to an incremental pull. But when fetching files data, instead
      of using the list of a changesets and manifests that we fetched via the
      "changesetdata" command, we do a linear scan of the repo and resolve the
      changeset and manifest nodes along with the manifest linkrevs.
      
      Differential Revision: https://phab.mercurial-scm.org/D5135
      00a4cd36
  2. Oct 16, 2018
  3. Sep 26, 2018
    • Gregory Szorc's avatar
      exchangev2: recognize narrow patterns when pulling · 55836a34
      Gregory Szorc authored
      pulloperation instances were recently taught to record file
      include and exclude patterns to facilitate narrow file transfer.
      Teaching the exchangev2 code to transfer a subset of files is
      as simple as constructing a narrow matcher from these patterns and
      filtering all seen file paths through it.
      
      Keep in mind that this change only influences file data: we're
      still fetching all changeset and manifest data. So, there's still
      a ton of "partial clone" to implement in exchangev2.
      
      On a personal note, I derive gratification that this feature requires
      very few lines of new code to implement.
      
      To test this, we implemented a minimal extension which allows us to specify
      --include/--exclude to clone. While the narrow extension provides these
      arguments, I explicitly wanted to test this functionality without the
      narrow extension enabled, as that extension monkeypatches various things
      and I want to isolate the behavior of core Mercurial.
      
      Differential Revision: https://phab.mercurial-scm.org/D5132
      55836a34
  4. Oct 09, 2018
    • Gregory Szorc's avatar
      sqlitestore: file storage backend using SQLite · fed697fa
      Gregory Szorc authored
      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
      fed697fa
  5. Oct 16, 2018
  6. Sep 21, 2018
    • Matt Harbison's avatar
      lfs: autoload the extension when cloning from repo with lfs enabled · 6637b079
      Matt Harbison authored
      This is based on a patch by Gregory Szorc.  I made small adjustments to
      clean up the messaging when the server has the extension enabled, but the
      client has it disabled (to prevent autoloading).  Additionally, I added
      a second server capability to distinguish between the server having the
      extension enabled, and the server having LFS commits.  This helps prevent
      unnecessary requirement propagation- the client shouldn't add a requirement
      that the server doesn't have, just because the server had the extension
      loaded.  The TODO I had about advertising a capability when the server can
      natively serve up blobs isn't relevant anymore (we've had 2 releases that
      support this), so I dropped it.
      
      Currently, we lazily add the "lfs" requirement to a repo when we first
      encounter LFS data. Due to a pretxnchangegroup hook that looks for LFS
      data, this can happen at the end of clone.
      
      Now that we have more control over how repositories are created, we can
      do better.
      
      This commit adds a repo creation option to add the "lfs" requirement.
      hg.clone() sets this creation option if the remote peer is advertising
      lfs usage (as opposed to just support needed to push).
      
      So, what this change effectively does is have cloned repos
      automatically inherit the "lfs" requirement.
      
      Differential Revision: https://phab.mercurial-scm.org/D5130
      6637b079
  7. Oct 16, 2018
  8. Aug 31, 2018
  9. Oct 11, 2018
  10. Oct 16, 2018
  11. Oct 14, 2018
  12. Oct 13, 2018
  13. Oct 14, 2018
  14. Oct 15, 2018
  15. Oct 08, 2018
    • Georges Racinet's avatar
      rust: rustlazyancestors.__contains__ · 72b94f94
      Georges Racinet authored
      This changeset provides a Rust implementation of
      the iteration performed by lazyancestor.__contains__
      
      It has the advantage over the Python iteration to use
      the 'seen' set encapsuled into the dedicated iterator (self._containsiter),
      rather than storing emitted items in another set (self._containsseen),
      and hence should reduce the memory footprint.
      
      Also, there's no need to convert intermediate emitted revisions back into
      Python integers.
      
      At this point, it would be tempting to implement the whole lazyancestor object
      in Rust, but that would lead to more C wrapping code (two objects) for
      little expected benefits.
      72b94f94
  16. Oct 14, 2018
  17. Sep 27, 2018
    • Georges Racinet's avatar
      rust: hooking into Python code · 9cadb0f5
      Georges Racinet authored
      We introduce a new class called 'rustlazyancestors'
      in the ancestors module, which is used only if
      parsers.rustlazyancestors does exist.
      
      The implementation of __contains__ stays unchanged,
      but is now backed by the Rust iterator. It would
      probably be a good candidate for further development,
      though, as it is mostly looping, and duplicates the
      'seen' set.
      
      The Rust code could be further optimized, however it already
      gives rise to performance improvements:
      
      median timing from hg perfancestors:
      - on pypy:
          before: 0.077566s
          after:  0.016676s -79%
      - on mozilla central:
          before: 0.190037s
          after:  0.082225s -58%
      - on a private repository (about one million revisions):
          before: 0.567085s
          after:  0.108816s -80%
      - on another private repository (about 400 000 revisions):
          before: 1.440918s
          after:  0.290116s -80%
      
      median timing for hg perfbranchmap base
      - on pypy:
          before:  1.383413s
          after:   0.507993s -63%
      - on mozilla central:
          before:  2.821940s
          after:   1.258902s -55%
      - on a private repository (about one million revisions):
          before: 77.065076s
          after:   16.158475s -80%
      - on another private repository (about 401 000 revisions):
          before:  7.835503s
          after:   3.545331s -54%
      9cadb0f5
  18. Oct 14, 2018
  19. Oct 12, 2018
  20. Oct 13, 2018
  21. Oct 12, 2018
  22. Oct 13, 2018
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