perf(go): skip empty parsed raw payloads

go/vehicle-gateway/internal/history/writer_test.go

@@ -126,6 +126,27 @@ func TestWriterChunksOversizedParsedJSON(t *testing.T) {
 	}
 }
 
+func TestWriterLeavesParsedJSONEmptyWhenNoParsedPayload(t *testing.T) {
+	exec := &recordingExec{}
+	writer := NewWriter(exec)
+	env := sampleEnvelope()
+	env.Parsed = nil
+	env.ParseStatus = envelope.ParseBadFrame
+	env.ParseError = "invalid frame checksum"
+
+	if err := writer.AppendRawFrame(context.Background(), env); err != nil {
+		t.Fatalf("AppendRawFrame() error = %v", err)
+	}
+
+	rawInsert := findSQL(exec.calls, "INSERT INTO raw_")
+	if strings.Contains(rawInsert, "'{}'") || strings.Contains(rawInsert, "'null'") {
+		t.Fatalf("raw insert should not store empty parsed_json payload: %s", rawInsert)
+	}
+	if !strings.Contains(rawInsert, "'invalid frame checksum'") {
+		t.Fatalf("raw insert should keep parse error: %s", rawInsert)
+	}
+}
+
 func TestWriterSkipsSparseDerivedRows(t *testing.T) {
 	exec := &recordingExec{}
 	writer := NewWriter(exec)