view mercurial/txnutil.py @ 40746:82c189c511bd

perf: add a `clear-revlogs` flag to `perfbookmarks`

This flag (off by default) makes it possible to enable the refresh of the
changelog and revlog. This is useful to check for costly side effects of
bookmark loading.

Usually, these side effects are shared with other logics (eg: tags).

example output in my mercurial repo (with 1 bookmark, so not a great example):
$ hg perfbookmarks
! wall 0.000044
$ hg perfbookmarks --clear-revlogs
! wall 0.001380

# txnutil.py - transaction related utilities
#
#  Copyright FUJIWARA Katsunori <[e-mail]> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import errno

from . import (
    encoding,
)

def mayhavepending(root):
    '''return whether 'root' may have pending changes, which are
    visible to this process.
    '''
    return root == encoding.environ.get('HG_PENDING')

def trypending(root, vfs, filename, **kwargs):
    '''Open  file to be read according to HG_PENDING environment variable

    This opens '.pending' of specified 'filename' only when HG_PENDING
    is equal to 'root'.

    This returns '(fp, is_pending_opened)' tuple.
    '''
    if mayhavepending(root):
        try:
            return (vfs('%s.pending' % filename, **kwargs), True)
        except IOError as inst:
            if inst.errno != errno.ENOENT:
                raise
    return (vfs(filename, **kwargs), False)