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revset: optimize "draft() & ::x" pattern
ClosedPublic

Authored by quark on Aug 18 2017, 12:50 AM.

Details

Summary

The draft() & ::x type query could be common for selecting one or more
draft feature branches being worked on.

Before this patch, ::x may travel through the changelog DAG for a long
distance until it gets a smaller revision number than min(draft()). It
could be very slow on long changelog with distant (in terms of revision
numbers) drafts.

This patch adds a fast path for this situation, and will stop traveling the
changelog DAG once ::x hits a non-draft revision.

The fast path also works for secret() and not public().

To measure the performance difference, I used drawdag to create a repo that
emulates distant drafts:

        DRAFT4
         |
        DRAFT3 # draft
        /
PUBLIC9999 # public
    |
PUBLIC9998
    |
    .   DRAFT2
    .    |
    .   DRAFT1 # draft
    |   /
PUBLIC0001 # public

And measured the performance using the repo:

(BEFORE)
$ hg perfrevset 'draft() & ::(DRAFT2+DRAFT4)'
! wall 0.017132 comb 0.010000 user 0.010000 sys 0.000000 (best of 156)
$ hg perfrevset 'draft() & ::(all())'
! wall 0.024221 comb 0.030000 user 0.030000 sys 0.000000 (best of 113)
(AFTER)
$ hg perfrevset 'draft() & ::(DRAFT2+DRAFT4)'
! wall 0.000243 comb 0.000000 user 0.000000 sys 0.000000 (best of 9303)
$ hg perfrevset 'draft() & ::(all())'
! wall 0.004319 comb 0.000000 user 0.000000 sys 0.000000 (best of 655)

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Event Timeline

quark created this revision.Aug 18 2017, 12:50 AM
quark edited the summary of this revision. (Show Details)Aug 18 2017, 12:51 AM
quark updated this revision to Diff 1057.Aug 18 2017, 12:56 AM
quark edited the summary of this revision. (Show Details)Aug 18 2017, 1:14 AM
quark updated this revision to Diff 1058.Aug 18 2017, 1:25 AM

I'll review in more detail later, but just a quick comment for now

mercurial/revset.py
1603

Isn't "getphase(repo,rev) >= keepphase" more natural? You'd then replace phasenamemap by something like

minphase = {
    '_notpublic': draft,
    'draft': draft,
    'secret': secret,
}
quark updated this revision to Diff 1059.Aug 18 2017, 1:44 AM
quark updated this revision to Diff 1071.Aug 18 2017, 10:50 AM
quark marked an inline comment as done.Aug 18 2017, 10:51 AM
quark added inline comments.
mercurial/revset.py
1603

Good point. Thanks!

quark marked an inline comment as done.Aug 18 2017, 11:04 AM

By the way, take your time. This is not an urgent change.

tests/test-revset.t
4344

Need to change to just P5.

quark added inline comments.Aug 18 2017, 11:07 AM
mercurial/dagop.py
93

Could use revs.filter instead.

quark updated this revision to Diff 1074.Aug 18 2017, 1:18 PM
quark marked 2 inline comments as done.Aug 18 2017, 1:19 PM
quark updated this revision to Diff 1075.Aug 18 2017, 1:27 PM
yuja added a subscriber: yuja.Aug 19 2017, 12:30 AM
yuja added inline comments.
mercurial/revsetlang.py
432

FWIW, I wrote placeholder matcher once, which could be used as follows.

m = _matchtree('_() & ::_', ('and', ta, tb))
if m and getsymbol(m[1]) in _fastphases:
    ...

https://bitbucket.org/yuja/hg-work/commits/6c0ae642d86a188af8e940e430522e915f478b25

This is outdated and needs modification, but do you like it?

quark added inline comments.Aug 19 2017, 1:33 AM
mercurial/revsetlang.py
432

Yes! That's much shorter (I had to copy the trees from debugshell) and more robust (no fragile len(x) >= 3 handling).

For performance concerns, I think it's fine. Practically, revset parsing is hardly a bottleneck. With chg, _treecache could be pre-populated.

yuja added inline comments.Aug 19 2017, 3:14 AM
mercurial/revsetlang.py
432

I'll rebase my patches then. I'm sure that isn't trivial because I introduced the order flag.

quark added inline comments.Aug 19 2017, 1:44 PM
mercurial/revsetlang.py
432

Maybe order could be removed from AST since they can be inferred during tree traversal? I have a draft D451 that verifies the idea.

quark planned changes to this revision.Aug 24 2017, 12:06 AM

Let's wait for my revset order and Yuya's matchtree patches first.

quark updated this revision to Diff 1570.Sep 1 2017, 9:24 PM
quark updated this revision to Diff 1571.Sep 1 2017, 9:28 PM
yuja accepted this revision.Sep 3 2017, 10:08 AM

Queued, thanks. I've removed _() because _phaseandancestors() is an internal function.

mercurial/revset.py
1607

revs & phasecache.getrevset(repo, [phasename]) might be
slightly faster, but I don't think it would make any noticeable difference.

mercurial/revsetlang.py
416

Perhaps ::x & phasename() can be optimized, too.

This revision is now accepted and ready to land.Sep 3 2017, 10:08 AM
This revision was automatically updated to reflect the committed changes.