Update logic to remove element from slice, avoid allocations (open-te…

…lemetry#8856)

Signed-off-by: Bogdan Drutu <bogdandrutu@gmail.com>

exporter/exporterhelper/internal/persistent_storage.go

@@ -349,13 +349,14 @@ func (pcs *persistentContiguousStorage) itemDispatchingStart(ctx context.Context
 
 // itemDispatchingFinish removes the item from the list of currently dispatched items and deletes it from the persistent queue
 func (pcs *persistentContiguousStorage) itemDispatchingFinish(ctx context.Context, index itemIndex) error {
-	var updatedDispatchedItems []itemIndex
-	for _, it := range pcs.currentlyDispatchedItems {
-		if it != index {
-			updatedDispatchedItems = append(updatedDispatchedItems, it)
+	lenCDI := len(pcs.currentlyDispatchedItems)
+	for i := 0; i < lenCDI; i++ {
+		if pcs.currentlyDispatchedItems[i] == index {
+			pcs.currentlyDispatchedItems[i] = pcs.currentlyDispatchedItems[lenCDI-1]
+			pcs.currentlyDispatchedItems = pcs.currentlyDispatchedItems[:lenCDI-1]
+			break
 		}
 	}
-	pcs.currentlyDispatchedItems = updatedDispatchedItems
 
 	setOp := storage.SetOperation(currentlyDispatchedItemsKey, itemIndexArrayToBytes(pcs.currentlyDispatchedItems))
 	deleteOp := storage.DeleteOperation(getItemKey(index))

exporter/exporterhelper/internal/persistent_storage_test.go

@@ -235,7 +235,7 @@ func TestPersistentStorage_CurrentlyProcessedItems(t *testing.T) {
 	}
 
 	// The queue should be now empty
-	requireCurrentlyDispatchedItemsEqual(t, newPs, nil)
+	requireCurrentlyDispatchedItemsEqual(t, newPs, []itemIndex{})
 	assert.Eventually(t, func() bool {
 		return newPs.size() == 0
 	}, 5*time.Second, 10*time.Millisecond)