fix: handle backend issue list regressions

server/topic.go

@@ -3535,6 +3535,13 @@ func (t *Topic) replyGetData(sess *Session, asUid types.Uid, asChan bool, req *M
 			} else if ok {
 				messages = filterHotMessagesForUser(hotMessages, asUid)
 			}
+		} else if shouldTryHotMessageSupplement(t.cat, opts, len(messages)) {
+			hotMessages, ok, cacheErr := store.GetHotMessages(t.tenantID, t.name, opts, hotMessageRangeLimit(opts))
+			if cacheErr != nil {
+				logs.Warn.Printf("get.data hot message supplement failed topic=%s user=%s: %v", t.name, asUid.UserId(), cacheErr)
+			} else if ok {
+				messages = mergeHotMessageSupplement(messages, filterHotMessagesForUser(hotMessages, asUid), opts)
+			}
 		}
 
 		// Push the list of messages to the client as {data}.
@@ -3595,6 +3602,28 @@ func shouldTryHotMessageFallback(cat types.TopicCat, lastID int64, opts *types.Q
 	return lastID <= 0 || opts.Since >= floor
 }
 
+func shouldTryHotMessageSupplement(cat types.TopicCat, opts *types.QueryOpt, got int) bool {
+	if cat != types.TopicCatGrp || opts == nil || opts.IfModifiedSince != nil ||
+		!opts.User.IsZero() || opts.Topic != "" || len(opts.IdRanges) > 0 ||
+		opts.Since <= 0 || opts.Before <= opts.Since {
+		return false
+	}
+	expected := hotMessageRangeLimit(opts)
+	return expected > 0 && got > 0 && got < expected
+}
+
+func hotMessageRangeLimit(opts *types.QueryOpt) int {
+	if opts == nil || opts.Since <= 0 || opts.Before <= opts.Since {
+		return hotMessageFallbackLimit(opts)
+	}
+	expected := opts.Before - opts.Since
+	limit := hotMessageFallbackLimit(opts)
+	if limit <= 0 || int64(limit) > expected {
+		return int(expected)
+	}
+	return limit
+}
+
 func hotMessageFallbackLimit(opts *types.QueryOpt) int {
 	if opts != nil && opts.Limit > 0 {
 		return opts.Limit
@@ -3602,6 +3631,36 @@ func hotMessageFallbackLimit(opts *types.QueryOpt) int {
 	return 1
 }
 
+func mergeHotMessageSupplement(messages, hotMessages []types.Message, opts *types.QueryOpt) []types.Message {
+	if len(messages) == 0 || len(hotMessages) == 0 {
+		return messages
+	}
+	bySeq := make(map[int64]types.Message, len(hotMessages)+len(messages))
+	for _, msg := range hotMessages {
+		bySeq[msg.SeqId] = msg
+	}
+	for _, msg := range messages {
+		bySeq[msg.SeqId] = msg
+	}
+	merged := make([]types.Message, 0, len(bySeq))
+	for _, msg := range bySeq {
+		if opts != nil {
+			if opts.Since > 0 && msg.SeqId < opts.Since {
+				continue
+			}
+			if opts.Before > 0 && msg.SeqId >= opts.Before {
+				continue
+			}
+		}
+		merged = append(merged, msg)
+	}
+	sort.Slice(merged, func(i, j int) bool { return merged[i].SeqId > merged[j].SeqId })
+	if opts != nil && opts.Limit > 0 && len(merged) > opts.Limit {
+		merged = merged[:opts.Limit]
+	}
+	return merged
+}
+
 func filterHotMessagesForUser(messages []types.Message, asUid types.Uid) []types.Message {
 	if len(messages) == 0 {
 		return messages