return nil when their are no results

common/aws/dynamodb/client.go

@@ -187,6 +187,10 @@ func (c *Client) QueryIndexWithPagination(ctx context.Context, tableName string,
 		return QueryResult{}, err
 	}
 
+	if len(response.Items) == 0 {
+		return QueryResult{Items: nil, LastEvaluatedKey: nil}, nil
+	}
+
 	// Return the items and the pagination token
 	return QueryResult{
 		Items:            response.Items,

common/aws/dynamodb/client_test.go

@@ -337,7 +337,22 @@ func TestQueryIndexPaginationSingleItem(t *testing.T) {
 			Value: "0",
 		}}, 1, lastEvaluatedKey)
 	assert.NoError(t, err)
-	assert.Len(t, queryResult.Items, 0)
+	assert.Nil(t, queryResult.Items)
+	assert.Nil(t, queryResult.LastEvaluatedKey)
+}
+
+func TestQueryIndexPaginationNoStoredItems(t *testing.T) {
+	tableName := "ProcessingWithPaginationNoItem"
+	createTable(t, tableName)
+	indexName := "StatusIndex"
+
+	ctx := context.Background()
+	queryResult, err := dynamoClient.QueryIndexWithPagination(ctx, tableName, indexName, "BlobStatus = :status", commondynamodb.ExpresseionValues{
+		":status": &types.AttributeValueMemberN{
+			Value: "0",
+		}}, 1, nil)
+	assert.NoError(t, err)
+	assert.Nil(t, queryResult.Items)
 	assert.Nil(t, queryResult.LastEvaluatedKey)
 }
 

disperser/common/blobstore/blob_metadata_store.go

@@ -119,6 +119,11 @@ func (s *BlobMetadataStore) GetBlobMetadataByStatusWithPagination(ctx context.Co
 		return nil, nil, err
 	}
 
+	// When their are no more results to fetch, the LastEvaluatedKey is nil
+	if queryResult.Items == nil && queryResult.LastEvaluatedKey == nil {
+		return nil, nil, nil
+	}
+
 	metadata := make([]*disperser.BlobMetadata, len(queryResult.Items))
 	for i, item := range queryResult.Items {
 		metadata[i], err = UnmarshalBlobMetadata(item)

disperser/common/blobstore/blob_metadata_store_test.go

@@ -175,6 +175,16 @@ func TestBlobMetadataStoreOperationsWithPagination(t *testing.T) {
 	})
 }
 
+func TestBlobMetadataStoreOperationsWithPaginationNoStoredBlob(t *testing.T) {
+	ctx := context.Background()
+	// Query BlobMetadataStore for a blob that does not exist
+	// This should return nil for both the blob and lastEvaluatedKey
+	processing, lastEvaluatedKey, err := blobMetadataStore.GetBlobMetadataByStatusWithPagination(ctx, disperser.Processing, 1, nil)
+	assert.NoError(t, err)
+	assert.Nil(t, processing)
+	assert.Nil(t, lastEvaluatedKey)
+}
+
 func deleteItems(t *testing.T, keys []commondynamodb.Key) {
 	_, err := dynamoClient.DeleteItems(context.Background(), metadataTableName, keys)
 	assert.NoError(t, err)