roachtest: clarify cdc scan rate calculation

DarrylWong · DarrylWong · commit 5445d58bfdcb · 2025-09-09T11:37:17.000-04:00
diff --git a/pkg/cmd/roachtest/tests/cdc_bench.go b/pkg/cmd/roachtest/tests/cdc_bench.go
@@ -78,6 +78,9 @@ func registerCDCBench(r registry.Registry) {
 		if len(histograms.Summaries) != 1 {
 			return nil, errors.Errorf("expected exactly 1 histogram summary, got %d", len(histograms.Summaries))
 		}
+		// CDC scan tests export the scan rate (rows per second) as a single
+		// duration value in nanoseconds, set as the upper bound of the histogram.
+		// This convoluted scheme was cargo-culted from the restore test.
 		scanRate = float64(histograms.Summaries[0].HighestTrackableValue) / float64(time.Second)
 
 		// Add scan rate metric (higher is better)

Original file line number	Diff line number	Diff line change
`@@ -78,6 +78,9 @@ func registerCDCBench(r registry.Registry) {`
`78`	`78`	`if len(histograms.Summaries) != 1 {`
`79`	`79`	`return nil, errors.Errorf("expected exactly 1 histogram summary, got %d", len(histograms.Summaries))`
`80`	`80`	`}`
	`81`	`+ // CDC scan tests export the scan rate (rows per second) as a single`
	`82`	`+ // duration value in nanoseconds, set as the upper bound of the histogram.`
	`83`	`+ // This convoluted scheme was cargo-culted from the restore test.`
`81`	`84`	`scanRate = float64(histograms.Summaries[0].HighestTrackableValue) / float64(time.Second)`
`82`	`85`
`83`	`86`	`// Add scan rate metric (higher is better)`