comparison mercurial/tags.py @ 42237:9f45d3d526f9

hgtagsfnodescache: inherit fnode from parent when possible

If a changeset does not update the content of `.hgtags`, it means it will use
the same file-node (for `.hgtags`) as its parents. In this case we can
directly reuse the parent's file-node.

We use this property when updating the `hgtagsfnodescache` taking a faster path
if we already have a cached value for the parents of the node we are looking
at.

Doing so provides a large performance boost when looking at a lot of fnodes,
especially on repository with very large manifest:

timing for `tagsmod.fnoderevs(ui, repo, repo.changelog.revs())`

mercurial: (41907 revisions, 1923 files)

    before: 6.9 seconds
    after:  2.7 seconds (-54%)

pypy: (96266 revisions, 5198 files)

    before: 80 seconds
    after:  20 seconds (-75%)

mozilla-central: (463411 revisions, 272080 files)

    before: 7166.4 seconds
    after:    47.8 seconds (-99%, x150 speedup)

On a copy of mozilla-try with about 35K heads ans 1.7M changesets, this moves
the computation from many hours to a couple of minutes, making it more
interesting to do a full warm up of this cache before computing tags (from a
cold cache).

There seems to be other performance low hanging fruits, like avoiding the use of
changectx or a more revision centric logic. However, the new code is fast enough
for my needs right now.

42236:2930b31383af

from .node import (
    bin,
    hex,
    nullid,
    short,
)
from .i18n import _
from . import (
    encoding,

        # If we get here, the entry is either missing or invalid.

        if not computemissing:
            return None

        # Populate missing entry.
        try:
            fnode = ctx.filenode('.hgtags')
        except error.LookupError:
            # No .hgtags file on this revision.
            fnode = nullid

        self._writeentry(offset, properprefix, fnode)
        return fnode

    def setfnode(self, node, fnode):

42237:9f45d3d526f9

from .node import (
    bin,
    hex,
    nullid,
    nullrev,
    short,
)
from .i18n import _
from . import (
    encoding,

        # If we get here, the entry is either missing or invalid.

        if not computemissing:
            return None

        fnode = None
        cl = self._repo.changelog
        p1rev, p2rev = cl._uncheckedparentrevs(rev)
        p1node = cl.node(p1rev)
        p1fnode = self.getfnode(p1node, computemissing=False)
        if p2rev != nullrev:
            # There is some no-merge changeset where p1 is null and p2 is set
            # Processing them as merge is just slower, but still gives a good
            # result.
            p2node = cl.node(p1rev)
            p2fnode = self.getfnode(p2node, computemissing=False)
            if p1fnode != p2fnode:
                # we cannot rely on readfast because we don't know against what
                # parent the readfast delta is computed
                p1fnode = None
        if p1fnode is not None:
            mctx = ctx.manifestctx()
            fnode = mctx.readfast().get('.hgtags')
            if fnode is None:
                fnode = p1fnode
        if fnode is None:
            # Populate missing entry.
            try:
                fnode = ctx.filenode('.hgtags')
            except error.LookupError:
                # No .hgtags file on this revision.
                fnode = nullid

        self._writeentry(offset, properprefix, fnode)
        return fnode

    def setfnode(self, node, fnode):