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revision: stop retrieving reference twice 

When queueing up references for the revision walk, `handle_one_ref()`
will resolve the reference's object ID via `get_reference()` and then
queue the ID as pending object via `add_pending_oid()`. But given that
`add_pending_oid()` is only a thin wrapper around `add_pending_object()`
which fist calls `get_reference()`, we effectively resolve the reference
twice and thus duplicate some of the work.

Fix the issue by instead calling `add_pending_object()` directly, which
takes the already-resolved object as input. In a repository with lots of
refs, this translates into a near 10% speedup:

    Benchmark #1: HEAD~: rev-list --unsorted-input --objects --quiet --not --all --not $newrev
      Time (mean ± σ):      5.015 s ±  0.038 s    [User: 4.698 s, System: 0.316 s]
      Range (min … max):    4.970 s …  5.089 s    10 runs

    Benchmark #2: HEAD: rev-list --unsorted-input --objects --quiet --not --all --not $newrev
      Time (mean ± σ):      4.606 s ±  0.029 s    [User: 4.260 s, System: 0.345 s]
      Range (min … max):    4.565 s …  4.657 s    10 runs

    Summary
      'HEAD: rev-list --unsorted-input --objects --quiet --not --all --not $newrev' ran
        1.09 ± 0.01 times faster than 'HEAD~: rev-list --unsorted-input --objects --quiet --not --all --not $newrev'

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
maint
Patrick Steinhardt 2021-08-09 10:11:54 +02:00 committed by Junio C Hamano
parent f45022dc2f
commit bf9c0cbddb
1 changed files with 1 additions and 1 deletions
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revision.c
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@ -1534,7 +1534,7 @@ static int handle_one_ref(const char *path, const struct object_id *oid,

object = get_reference(cb->all_revs, path, oid, cb->all_flags);
add_rev_cmdline(cb->all_revs, object, path, REV_CMD_REF, cb->all_flags);
add_pending_oid(cb->all_revs, path, oid, cb->all_flags);
add_pending_object(cb->all_revs, object, path);
return 0;
}