Fix issue with delta calculation when previous interval has no telemetry

application/src/main/java/org/thingsboard/server/service/subscription/DefaultTbEntityDataSubscriptionService.java

@@ -314,9 +314,9 @@ public class DefaultTbEntityDataSubscriptionService implements TbEntityDataSubsc
                             ReadTsKvQueryInfo queryInfo = queries.get(queryResult.getQueryId());
                             ComparisonTsValue comparisonTsValue = entityData.getAggLatest().computeIfAbsent(queryInfo.getKey().getId(), agg -> new ComparisonTsValue());
                             if (queryInfo.isPrevious()) {
-                                comparisonTsValue.setPrevious(queryResult.toTsValue());
+                                comparisonTsValue.setPrevious(queryResult.toTsValue(queryInfo.getQuery()));
                             } else {
-                                comparisonTsValue.setCurrent(queryResult.toTsValue());
+                                comparisonTsValue.setCurrent(queryResult.toTsValue(queryInfo.getQuery()));
                                 lastTsMap.put(queryInfo.getQuery().getKey(), queryResult.getLastEntryTs());
                             }
                         }

common/data/src/main/java/org/thingsboard/server/common/data/kv/ReadTsKvQueryResult.java

@@ -42,9 +42,14 @@ public class ReadTsKvQueryResult {
         }
     }
 
-    public TsValue toTsValue() {
+    public TsValue toTsValue(ReadTsKvQuery query) {
         if (data == null || data.isEmpty()) {
-            return TsValue.EMPTY;
+            if (Aggregation.SUM.equals(query.getAggregation()) || Aggregation.COUNT.equals(query.getAggregation())) {
+                long ts = query.getStartTs() + (query.getEndTs() - query.getStartTs()) / 2;
+                return new TsValue(ts, "0");
+            } else {
+                return TsValue.EMPTY;
+            }
         }
         if (data.size() > 1) {
             throw new RuntimeException("Query Result has multiple data points!");

ui-ngx/src/app/core/api/entity-data-subscription.ts

@@ -165,7 +165,11 @@ export class EntityDataSubscription {
           if (key.comparisonResultType === ComparisonResultType.DELTA_ABSOLUTE) {
             value = currentVal - prevVal;
           } else {
-            value = (currentVal - prevVal) / prevVal * 100;
+            if(prevVal === 0){
+              value = 100;
+            } else {
+              value = (currentVal - prevVal) / prevVal * 100;
+            }
           }
         } else {
           value = '';