perf: Don't re-process events as outliers

src/service/rooms/event_handler/handle_outlier_pdu.rs

@@ -77,6 +77,13 @@ where
 	incoming_pdu
 		.insert("event_id".to_owned(), CanonicalJsonValue::String(event_id.as_str().to_owned()));
 
+	if let Ok(pdu_event) = self.services.timeline.get_pdu(event_id).await {
+		debug!(
+			"Already have event {event_id} as an outlier or timeline event, not re-processing"
+		);
+		return Ok((pdu_event, incoming_pdu));
+	}
+
 	let pdu_event = serde_json::from_value::<PduEvent>(
 		serde_json::to_value(&incoming_pdu).expect("CanonicalJsonObj is a valid JsonValue"),
 	)