revset: inline parents computation to reuse the input argument Before this change, using `heads(xxx)` would compute `xxx` multiple time. Once to select the possible candidates, and once to compute the parent set. The code used to compute parents is a direct copy past from the `parents` revset. We expect to replace it quickly in a later changeset. So we did not bother with extracting a function. In case where the input set is expensive to compute this provides a significant performance boost. (output are from contrib/revsetbenchmarks.py) revset: heads(matching(tip, "author")) plain min max first last reverse rev..rst rev..ast sort sor..rst sor..ast 0) 15.06746 14.92766 7.335694 15.03092 7.635580 15.04133 7.454806 15.27565 14.97796 14.87607 7.480900 1) 7.529300 49% 7.592152 50% 7.480548 7.544528 50% 7.421248 7.522279 50% 7.484876 7.613154 49% 7.599553 50% 7.561410 50% 7.508990 In other cases, with a faster input set, we still see a (smaller) performance boost. revset: heads(all()) plain min max first last reverse rev..rst rev..ast sort sor..rst sor..ast 0) 0.038994 0.035981 0.033345 0.035751 0.033569 0.039833 0.033653 0.035428 0.039483 0.035750 0.033657 1) 0.036359 93% 0.032613 90% 0.031479 94% 0.032790 91% 0.030681 91% 0.036456 91% 0.031128 92% 0.032461 91% 0.036276 91% 0.032721 91% 0.031024 92% revset: heads(-10000:-1) plain min max first last reverse rev..rst rev..ast sort sor..rst sor..ast 0) 0.004184 0.003576 0.003593 0.003628 0.003569 0.004277 0.003590 0.003719 0.004194 0.003659 0.003690 1) 0.003850 92% 0.003267 91% 0.003256 90% 0.003261 89% 0.003204 89% 0.003855 90% 0.003294 91% 0.003164 85% 0.003848 91% 0.003302 90% 0.003296 89% revset: (-5000:-1000) and heads(-10000:-1) plain min max first last reverse rev..rst rev..ast sort sor..rst sor..ast 0) 0.004730 0.003429 0.003359 0.003391 0.003369 0.004787 0.003418 0.003469 0.004772 0.003445 0.003454 1) 0.004277 90% 0.003430 0.003423 0.003353 0.003340 0.004250 88% 0.003387 0.003385 0.004325 90% 0.003413 0.003373 revset: heads(matching(tip, "author")) and -10000:-1 plain min max first last reverse rev..rst rev..ast sort sor..rst sor..ast 0) 8.250275 8.231453 7.508579 8.230028 7.529777 8.358590 7.531636 8.301830 8.137196 8.421402 7.540355 1) 7.474707 90% 7.587345 92% 7.486192 7.548340 91% 7.485288 7.659108 91% 7.485307 7.628890 91% 7.523479 92% 7.558384 89% 7.467524 revset: (-10000:-1) and heads(matching(tip, "author")) plain min max first last reverse rev..rst rev..ast sort sor..rst sor..ast 0) 8.341504 8.315248 7.489414 8.320746 7.548816 8.244137 7.514663 8.281701 8.218862 8.412644 7.456793 1) 7.553704 90% 7.570679 91% 7.391438 7.724237 92% 7.527400 7.570637 91% 7.580622 7.450912 89% 7.556154 91% 7.514726 89% 7.494328

--- a/mercurial/revset.py	Sun Jan 13 22:24:11 2019 +0100
+++ b/mercurial/revset.py	Mon Jan 14 16:53:55 2019 +0100
@@ -1168,9 +1168,18 @@
     # argument set should never define order
     if order == defineorder:
         order = followorder
-    s = getset(repo, subset, x, order=order)
-    ps = parents(repo, subset, x)
-    return s - ps
+    inputset = getset(repo, fullreposet(repo), x, order=order)
+    ps = set()
+    cl = repo.changelog
+    up = ps.update
+    parentrevs = cl.parentrevs
+    for r in inputset:
+        try:
+            up(parentrevs(r))
+        except error.WdirUnsupported:
+            up(p.rev() for p in repo[r].parents())
+    ps.discard(node.nullrev)
+    return subset & (inputset - ps)
 
 @predicate('hidden()', safe=True)
 def hidden(repo, subset, x):

--- a/tests/test-revset.t	Sun Jan 13 22:24:11 2019 +0100
+++ b/tests/test-revset.t	Mon Jan 14 16:53:55 2019 +0100
@@ -1427,12 +1427,10 @@
   $ hg debugrevspec -s '9: & heads(all())'
   * set:
   <filteredset
+    <baseset [9]>,
     <filteredset
-      <baseset [9]>,
-      <spanset+ 0:10>>,
-    <not
-      <filteredset
-        <baseset [9]>, set([0, 1, 2, 3, 4, 5, 6, 8])>>>
+      <spanset+ 0:10>,
+      <not set([0, 1, 2, 3, 4, 5, 6, 8])>>>
   9
 
  but should follow the order of the subset