Mercurial > hg
view tests/test-issue1877.t @ 17970:0b03454abae7
ancestor: faster algorithm for difference of ancestor sets
One of the major reasons rebase is slow in large repositories is
the computation of the detach set: the set of ancestors of the
changesets to rebase not in the destination parent. This is currently
done via a revset that does two walks all the way to the root of
the DAG. Instead of doing that, to find ancestors of a set <revs>
not in another set <common> we walk up the tree in reverse revision
number order, maintaining sets of nodes visited from <revs>, <common>
or both.
For the common case where the sets are close both topologically and
in revision number (relative to repository size), this has been
found to speed up rebase by around 15-20%. When the nodes are farther
apart and the DAG is highly branching, it is harder to say which
would win.
Here's how long computing the detach set takes in a linear repository
with over 400000 changesets, rebasing near tip:
Rebasing across 4 changesets
Revset method: 2.2s
New algorithm: 0.00015s
Rebasing across 250 changesets
Revset method: 2.2s
New algorithm: 0.00069s
Rebasing across 10000 changesets
Revset method: 2.4s
New algorithm: 0.019s
author | Siddharth Agarwal <sid0@fb.com> |
---|---|
date | Mon, 26 Nov 2012 11:46:51 -0800 |
parents | f2719b387380 |
children | ca275f7ec576 |
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http://mercurial.selenic.com/bts/issue1877 $ hg init a $ cd a $ echo a > a $ hg add a $ hg ci -m 'a' $ echo b > a $ hg ci -m'b' $ hg up 0 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ hg book main $ hg book * main 0:cb9a9f314b8b $ echo c > c $ hg add c $ hg ci -m'c' created new head $ hg book * main 2:d36c0562f908 $ hg heads changeset: 2:d36c0562f908 bookmark: main tag: tip parent: 0:cb9a9f314b8b user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: c changeset: 1:1e6c11564562 user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: b $ hg up 1e6c11564562 1 files updated, 0 files merged, 1 files removed, 0 files unresolved $ hg merge main 1 files updated, 0 files merged, 0 files removed, 0 files unresolved (branch merge, don't forget to commit) $ hg book main 2:d36c0562f908 $ hg ci -m'merge' $ hg book main 2:d36c0562f908 $ cd ..