changelog: lazily parse description
Before, the description field was converted to a localstr at parse
time. With this patch, we store the raw description and convert to
a localstr when it is first accessed.
We see a revset speedup for revsets that don't access the description:
author(mpm)
0.896565
0.914234
0.869085
date(2015)
0.878797
0.891980
0.862525
extra(rebase_source)
0.865446
0.912514
0.871500
author(mpm) or author(greg)
1.801832
1.860402
1.791589
date(2015) or branch(default)
0.968276
0.994673
0.974027
author(mpm) or desc(bug) or date(2015) or extra(rebase_source)
3.656193
3.721032
3.643593
As you can see, most of these revsets are already faster than from
before this refactoring: we have already offset the performance
loss from the introduction of the new class representing parsed
changelog entries!
os = <unloaded module 'os'>
os.system = <built-in function system>
os = <module 'os' from '?'>
util = <unloaded module 'util'>
util.system = <function system at 0x?>
util = <module 'mercurial.util' from '?'>
util.system = <function system at 0x?>
hgweb = <unloaded module 'hgweb'>
hgweb_mod = <unloaded module 'hgweb_mod'>
hgweb = <module 'mercurial.hgweb' from '?'>
fred = <unloaded module 're'>
re = <unloaded module 'sys'>
fred = <unloaded module 're'>
fred.sub = <function sub at 0x?>
fred = <proxied module 're'>
re = <unloaded module 'sys'>
re.stderr = <open file '<whatever>', mode 'w' at 0x?>
re = <proxied module 'sys'>
node = <module 'mercurial.node' from '?'>