Fix panic in query-frontend when combining results (#3683)

* Fix panic in query-frontend when combining results

* chlog

CHANGELOG.md

@@ -59,6 +59,7 @@
 * [BUGFIX] Use os path separator to split blocks path. [#3552](https://github.com/grafana/tempo/issues/3552) (@teyyubismayil)
 * [BUGFIX] Correctly parse traceql queries with > 1024 character attribute names or static values. [#3571](https://github.com/grafana/tempo/issues/3571) (@joe-elliott)
 * [BUGFIX] Fix span-metrics' subprocessors bug that applied wrong configs when running multiple tenants. [#3612](https://github.com/grafana/tempo/pull/3612) (@mapno)
+* [BUGFIX] Fix panic in query-frontend when combining results [#3683](https://github.com/grafana/tempo/pull/3683) (@mapno)
 
 ## v2.4.2
 

pkg/traceql/combine.go

@@ -81,6 +81,9 @@ func combineSearchResults(existing *tempopb.TraceSearchMetadata, incoming *tempo
 		existingStats, ok := existing.ServiceStats[service]
 		if !ok {
 			existingStats = &tempopb.ServiceStats{}
+			if existing.ServiceStats == nil {
+				existing.ServiceStats = make(map[string]*tempopb.ServiceStats)
+			}
 			existing.ServiceStats[service] = existingStats
 		}
 		existingStats.SpanCount = max(existingStats.SpanCount, incomingStats.SpanCount)

pkg/traceql/combine_test.go

@@ -220,6 +220,26 @@ func TestCombineResults(t *testing.T) {
 				},
 			},
 		},
+		{
+			name:     "existing ServiceStats is nil doesn't panic",
+			existing: &tempopb.TraceSearchMetadata{},
+			new: &tempopb.TraceSearchMetadata{
+				ServiceStats: map[string]*tempopb.ServiceStats{
+					"service1": {
+						SpanCount:  3,
+						ErrorCount: 2,
+					},
+				},
+			},
+			expected: &tempopb.TraceSearchMetadata{
+				ServiceStats: map[string]*tempopb.ServiceStats{
+					"service1": {
+						SpanCount:  3,
+						ErrorCount: 2,
+					},
+				},
+			},
+		},
 	}
 
 	for _, tc := range tcs {