Raise error on empty deltas for incremental indexing (#1375)

* Raise error on empty deltas for incremental indexing

* Format

Author: AlonsoGuevara

.semversioner/next-release/patch-20241106232311738461.json

@@ -0,0 +1,4 @@
+{
+  "type": "patch",
+  "description": "Raise error on empty deltas for inc indexing"
+}

graphrag/index/run/run.py

@@ -133,6 +133,11 @@ async def run_pipeline_with_config(
     if is_update_run and update_index_storage:
         delta_dataset = await get_delta_docs(dataset, storage)
 
+        # Fail on empty delta dataset
+        if delta_dataset.new_inputs.empty:
+            error_msg = "Incremental Indexing Error: No new documents to process."
+            raise ValueError(error_msg)
+
         delta_storage = update_index_storage.child("delta")
 
         # Run the pipeline on the new documents