view tests/fakemergerecord.py @ 42480:66c27df1be84

deltas: skip if projected delta size is bigger than previous snapshot

Before computing any delta, we get a basic estimation of the delta size we can
expect and the resulted compressed value. We then checks this projected size
against the `size(snapshotⁿ) > size(snapshotⁿ⁺¹)` constraint. This allows to
exclude potential base candidates before doing any expensive computation.

This only apply to the intermediate-snapshot case since this constraint only
apply to them.

For some pathological cases of a private repository this step provide a
significant performance boost (timing from `hg perfrevlogwrite`):

before: 14.115908 seconds
after:   3.145906 seconds

# Extension to write out fake unsupported records into the merge state
#
#

from __future__ import absolute_import

from mercurial import (
    merge,
    registrar,
)

cmdtable = {}
command = registrar.command(cmdtable)

@command(b'fakemergerecord',
         [(b'X', b'mandatory', None, b'add a fake mandatory record'),
          (b'x', b'advisory', None, b'add a fake advisory record')], '')
def fakemergerecord(ui, repo, *pats, **opts):
    with repo.wlock():
        ms = merge.mergestate.read(repo)
        records = ms._makerecords()
        if opts.get('mandatory'):
            records.append((b'X', b'mandatory record'))
        if opts.get('advisory'):
            records.append((b'x', b'advisory record'))
        ms._writerecords(records)