[darcs-users] --max-count versus --match=hash

[Gwern Branwen]

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So I was working on the darcsGetRevision function in Filestore, which
takes a hash (of some patch), asks the changelog (darcs changes) for
the XML information on it so it can generate a record with info like
date, author, summary, and files affect; and I replaced a call to just
'darcs changes' and then filtering through the entire list and taking
the head, with a --match='hash ' option. This was a great performance
boost, obviously (from >3s to
  * Sprints/2008-10

real	0m0.561s
user	0m0.508s
sys	0m0.048s
[12:01 PM] .6Mb$ time darcs changes --max-count=1 --quiet
- --match='hash
"20080823201731-f8758-f29ccdaaf70a878f58c10dc706a011af86da3374"'
Sat Aug 23 16:17:31 EDT 2008  Florent Becker
  * Sprints/2008-10

real	0m0.563s
user	0m0.512s
sys	0m0.052s
[12:01 PM] .6Mb$ time darcs changes --max-count=1 --quiet
- --match='hash
"20080823201731-f8758-f29ccdaaf70a878f58c10dc706a011af86da3374"'
Sat Aug 23 16:17:31 EDT 2008  Florent Becker
  * Sprints/2008-10

real	0m0.571s
user	0m0.520s
sys	0m0.044s
[12:02 PM] .6Mb$ time darcs changes --quiet --match='hash
"20080823201731-f8758-f29ccdaaf70a878f58c10dc706a011af86da3374"'
Sat Aug 23 16:17:31 EDT 2008  Florent Becker
  * Sprints/2008-10

real	0m0.595s
user	0m0.536s
sys	0m0.056s
[12:02 PM] .6Mb$ time darcs changes --quiet --match='hash
"20080823201731-f8758-f29ccdaaf70a878f58c10dc706a011af86da3374"'
Sat Aug 23 16:17:31 EDT 2008  Florent Becker
  * Sprints/2008-10

real	0m0.594s
user	0m0.540s
sys	0m0.052s
[12:02 PM] .6Mb$ time darcs changes --quiet --match='hash
"20080823201731-f8758-f29ccdaaf70a878f58c10dc706a011af86da3374"'
Sat Aug 23 16:17:31 EDT 2008  Florent Becker
  * Sprints/2008-10

real	0m0.587s
user	0m0.552s
sys	0m0.036s
[12:02 PM] .6Mb$ time darcs changes --quiet --match='hash
"20080823201731-f8758-f29ccdaaf70a878f58c10dc706a011af86da3374"'
Sat Aug 23 16:17:31 EDT 2008  Florent Becker
  * Sprints/2008-10

real	0m0.549s
user	0m0.496s
sys	0m0.052s

- --
gwern
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