From 5658ab3afea4a0a27b223e2c90b6725b389f8777 Mon Sep 17 00:00:00 2001
From: Tony Xiao <txiao@sentry.io>
Date: Wed, 3 Nov 2021 17:03:28 -0400
Subject: [PATCH] fix(suspect-spans): Span frequency should never exceed 100%

Because of the use of `count_unique(id)` to compute the number of transactions
that contain the span, and that it is an approximation, it is possible that we
will see some frequency values exceeding 100%. This clips the frequency value so
that this never happens.
---
 .../transactionSpans/suspectSpanCard.tsx             | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/static/app/views/performance/transactionSummary/transactionSpans/suspectSpanCard.tsx b/static/app/views/performance/transactionSummary/transactionSpans/suspectSpanCard.tsx
index e824f7d80635af..f95011f2bc7d35 100644
--- a/static/app/views/performance/transactionSummary/transactionSpans/suspectSpanCard.tsx
+++ b/static/app/views/performance/transactionSummary/transactionSpans/suspectSpanCard.tsx
@@ -190,14 +190,22 @@ function SpanCount(props: HeaderItemProps) {
     );
   }
 
+  // Because the frequency is computed using `count_unique(id)` internally,
+  // it is an approximate value. This means that it has the potential to be
+  // greater than `totals.count` when it shouldn't. So let's clip the
+  // frequency value to make sure we don't see values over 100%.
+  const frequency = defined(totals?.count)
+    ? Math.min(suspectSpan.frequency, totals!.count)
+    : suspectSpan.frequency;
+
   const value = defined(totals?.count) ? (
     <Tooltip
       title={tct('[frequency] out of [total] transactions contain this span', {
-        frequency: suspectSpan.frequency,
+        frequency,
         total: totals!.count,
       })}
     >
-      <span>{formatPercentage(suspectSpan.frequency / totals!.count)}</span>
+      <span>{formatPercentage(frequency / totals!.count)}</span>
     </Tooltip>
   ) : (
     String(suspectSpan.count)