# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@octobus.net>
# Date 1559726605 -7200
# Node ID b9ff059fd194a7e48f9963b3d80e747adefb760e
# Parent  d3b5cbe311d9fdc8b5aacf3736c41a6a97f984ed
discovery: be more conservative when adjusting the sample size

Since 5b34972a0094, the discovery will increase the sample size when it detect a
"complex" undecided set. However this detection focussed on the number of roots
only, this could regress discovery performance when the undecided set has many
roots that eventually get merged into a few heads.

To prevent such misbehavior, we adjust the logic to take in account both heads
and roots. The sample size will be increased only if both are especially large.

Performance testing on the same case as 5b34972a0094, does not show a
significant difference.

diff -r d3b5cbe311d9 -r b9ff059fd194 mercurial/setdiscovery.py
--- a/mercurial/setdiscovery.py	Thu May 16 16:22:20 2019 +0200
+++ b/mercurial/setdiscovery.py	Wed Jun 05 11:23:25 2019 +0200
@@ -242,13 +242,13 @@
 
         # update from roots
         revsroots = set(repo.revs('roots(%ld)', revs))
-        if not self._respectsize:
-            size = max(size, len(revsroots))
-
         childrenrevs = self._childrengetter()
-
         _updatesample(revs, revsroots, sample, childrenrevs)
         assert sample
+
+        if not self._respectsize:
+            size = max(size, min(len(revsroots), len(revsheads)))
+
         sample = _limitsample(sample, size)
         if len(sample) < size:
             more = size - len(sample)