[PATCH STABLE] obsolete: fix n^2 marker computation behavior
Pierre-Yves David
pierre-yves.david at ens-lyon.org
Tue Feb 23 13:19:22 UTC 2016
# HG changeset patch
# User Durham Goode <durham at fb.com>
# Date 1454629084 28800
# Thu Feb 04 15:38:04 2016 -0800
# Branch stable
# Node ID 61be787ee62ea5910b0e55b5b5743079fbea1457
# Parent 1bcb4f34b9f91a2e330966182f691664fbada1bc
# Available At http://hg.netv6.net/marmoute-wip/mercurial/
# hg pull http://hg.netv6.net/marmoute-wip/mercurial/ -r 61be787ee62e
obsolete: fix n^2 marker computation behavior
Previously, if you ran obsolete.createmarkers with a bunch of markers that did
not have successors (like when you do a prune), it encountered a n^2 computation
behavior because the loop would read the changelog (to get ctx.parents()), then
add a marker, in a loop. Adding a marker invalidated the computehidden cache,
and reading the changelog recomputed it.
This resulted in pruning 150 commits taking 150+ seconds in a large repo.
The fix is to break the reading part of the loop to be separate from the writing
part.
diff --git a/mercurial/obsolete.py b/mercurial/obsolete.py
--- a/mercurial/obsolete.py
+++ b/mercurial/obsolete.py
@@ -1223,10 +1223,11 @@ def createmarkers(repo, relations, flag=
metadata = {}
if 'user' not in metadata:
metadata['user'] = repo.ui.username()
tr = repo.transaction('add-obsolescence-marker')
try:
+ markerargs = []
for rel in relations:
prec = rel[0]
sucs = rel[1]
localmetadata = metadata.copy()
if 2 < len(rel):
@@ -1241,10 +1242,19 @@ def createmarkers(repo, relations, flag=
npare = None
if not nsucs:
npare = tuple(p.node() for p in prec.parents())
if nprec in nsucs:
raise error.Abort("changeset %s cannot obsolete itself" % prec)
+
+ # Creating the marker causes the hidden cache to become invalid,
+ # which causes recomputation when we ask for prec.parents() above.
+ # Resulting in n^2 behavior. So let's prepare all of the args
+ # first, then create the markers.
+ markerargs.append((nprec, nsucs, npare, localmetadata))
+
+ for args in markerargs:
+ nprec, nsucs, npare, localmetadata = args
repo.obsstore.create(tr, nprec, nsucs, flag, parents=npare,
date=date, metadata=localmetadata)
repo.filteredrevcache.clear()
tr.close()
finally:
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