@recaptime-dev's working patches + fork for Phorge, a community fork of Phabricator. (Upstream dev and stable branches are at upstream/main and upstream/stable respectively.)
hq.recaptime.dev/wiki/Phorge
phorge
phabricator
Fix explosive runtime of detectCopiedCode()
Summary:
Fixes T5041. Pretty sure this is the issue: if a diff contains a large number of identical lines longer than 30 characters, we end up paying O(N^2) for each set.
Instead, when N > 16, opt to pay 0.
Test Plan: Added a test which dropped from ~100s to ~0 after changes (this diff includes a reduced-strenght version of the test, since parsing a 4,000 line diff is a little bit pricey).
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T5041
Differential Revision: https://secure.phabricator.com/D9178
+47
+10
src/applications/differential/parser/DifferentialChangesetParser.php
+10
src/applications/differential/parser/DifferentialChangesetParser.php
···
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$added = array_map('trim', $hunk->getAddedLines());
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for (reset($added); list($line, $code) = each($added); ) {
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if (isset($map[$code])) { // We found a long matching line.
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+
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+
if (count($map[$code]) > 16) {
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// If there are a large number of identical lines in this diff,
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+
// don't try to figure out where this block came from: the
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// analysis is O(N^2), since we need to compare every line
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// against every other line. Even if we arrive at a result, it
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// is unlikely to be meaningful. See T5041.
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continue 2;
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+
}
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+
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$best_length = 0;
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foreach ($map[$code] as $val) { // Explore all candidates.
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list($file, $orig_line) = $val;
+37
src/applications/differential/storage/__tests__/DifferentialDiffTestCase.php
+37
src/applications/differential/storage/__tests__/DifferentialDiffTestCase.php
···
15
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ipull($copies, 1));
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}
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+
public function testDetectSlowCopiedCode() {
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+
// This tests that the detector has a reasonable runtime when a diff
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// contains a very large number of identical lines. See T5041.
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+
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+
$parser = new ArcanistDiffParser();
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+
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+
$line = str_repeat('x', 60);
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+
$oline = '-'.$line."\n";
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+
$nline = '+'.$line."\n";
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+
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$n = 1000;
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+
$oblock = str_repeat($oline, $n);
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+
$nblock = str_repeat($nline, $n);
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+
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+
$raw_diff = <<<EODIFF
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diff --git a/dst b/dst
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new file mode 100644
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index 0000000..1234567
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--- /dev/null
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+++ b/dst
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@@ -0,0 +1,{$n} @@
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{$nblock}
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diff --git a/src b/src
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deleted file mode 100644
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index 123457..0000000
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+
--- a/src
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+++ /dev/null
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@@ -1,{$n} +0,0 @@
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+
{$oblock}
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+
EODIFF;
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+
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$diff = DifferentialDiff::newFromRawChanges($parser->parseDiff($raw_diff));
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+
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+
$this->assertTrue(true);
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}
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+
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+
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}