roachtest/cdcbench: generate aggregate stats for cdc/scan tests

Adds aggregate metric for cdc/scan tests.
Adds one missing warehouse label in tpcc test.

Epic: none
Fixes: none

Author: csgourav

pkg/cmd/roachtest/tests/cdc_bench.go

@@ -92,6 +92,26 @@ func registerCDCBench(r registry.Registry) {
 				Run: func(ctx context.Context, t test.Test, c cluster.Cluster) {
 					runCDCBenchScan(ctx, t, c, scanType, rows, ranges, format)
 				},
+				PostProcessPerfMetrics: func(testName string, histograms *roachtestutil.HistogramMetric) (roachtestutil.AggregatedPerfMetrics, error) {
+					metrics := roachtestutil.AggregatedPerfMetrics{}
+
+					// Find the scan-rate summary
+					var scanRate float64
+					if len(histograms.Summaries) != 1 {
+						return nil, errors.Errorf("expected exactly 1 histogram summary, got %d", len(histograms.Summaries))
+					}
+					scanRate = float64(histograms.Summaries[0].HighestTrackableValue) / float64(time.Second)
+
+					// Add scan rate metric (higher is better)
+					metrics = append(metrics, &roachtestutil.AggregatedMetric{
+						Name:           "scan_rate",
+						Value:          roachtestutil.MetricPoint(scanRate),
+						Unit:           "rows/s",
+						IsHigherBetter: true,
+					})
+
+					return metrics, nil
+				},
 			})
 		}
 	}

pkg/cmd/roachtest/tests/tpcc.go

@@ -163,7 +163,7 @@ func getMaxWarehousesAboveEfficiency(
 	aggregatedMetrics = append(aggregatedMetrics, &roachtestutil.AggregatedMetric{
 		Name:           fmt.Sprintf("%s_max_warehouse", testName),
 		Value:          roachtestutil.MetricPoint(maxEfficientWarehouse),
-		Unit:           "",
+		Unit:           "warehouses",
 		IsHigherBetter: true,
 		// labels added here override any labels imported from the stats file.
 		// since we don't want to specify a warehouse label for this metric, we pass an empty label.