Loki Query Splitting: Fix bug for mixed split durations (#65925)

* Query splitting: fix next request group pointer calculation

* Update unit test

public/app/plugins/datasource/loki/querySplitting.test.ts

@@ -246,6 +246,20 @@ describe('runSplitQuery()', () => {
         expect(datasource.runQuery).toHaveBeenCalledTimes(3);
       });
     });
+    test('with mixed splitDuration runs the expected amount of queries', async () => {
+      const request = getQueryOptions<LokiQuery>({
+        targets: [
+          { expr: 'count_over_time({c="d"}[1m])', refId: 'A', splitDuration: '15m' },
+          { expr: '{a="b"}', refId: 'B', splitDuration: '15m' },
+          { expr: '{a="b"}', refId: 'C', splitDuration: '1h' },
+        ],
+        range: range1h,
+      });
+      await expect(runSplitQuery(datasource, request)).toEmitValuesWith(() => {
+        // 4 * 15m + 4 * 15m + 1 * 1h
+        expect(datasource.runQuery).toHaveBeenCalledTimes(9);
+      });
+    });
     test('with 1h/30m splitDuration and 1 log and 2 metric target runs 3 queries', async () => {
       const request = getQueryOptions<LokiQuery>({
         targets: [

public/app/plugins/datasource/loki/querySplitting.ts

@@ -154,11 +154,14 @@ export function runSplitGroupedQueries(datasource: LokiDatasource, requests: Lok
 
 function getNextRequestPointers(requests: LokiGroupedRequest, requestGroup: number, requestN: number) {
   // There's a pending request from the next group:
-  if (requests[requestGroup + 1]?.partition[requestN - 1]) {
+  for (let i = requestGroup + 1; i < requests.length; i++) {
-    return {
+    const group = requests[i];
-      nextRequestGroup: requestGroup + 1,
+    if (group.partition[requestN - 1]) {
-      nextRequestN: requestN,
+      return {
-    };
+        nextRequestGroup: i,
+        nextRequestN: requestN,
+      };
+    }
   }
   return {
     // Find the first group where `[requestN - 1]` is defined