Close dag fetcher iterables once finished

db/fetcher/dag.go

@@ -66,6 +66,13 @@ func (hf *HeadFetcher) Start(ctx context.Context, txn core.Txn, spans core.Spans
 	}
 
 	var err error
+	if hf.kvIter != nil {
+		// If an existing iterator is to be replaced, we must still may sure it is properly closed
+		err = hf.kvIter.Close()
+		if err != nil {
+			return err
+		}
+	}
 	hf.kvIter, err = txn.Headstore().Query(ctx, q)
 	if err != nil {
 		return err
@@ -133,6 +140,10 @@ func (hf *HeadFetcher) FetchNext() (*cid.Cid, error) {
 	return hf.cid, nil
 }
 
+func (hf *HeadFetcher) Close() error {
+	return hf.kvIter.Close()
+}
+
 /*
 // List returns the list of current heads plus the max height.
 // @todo Document Heads.List function

query/graphql/planner/dagscan.go

@@ -87,7 +87,9 @@ func (h *headsetScanNode) Values() map[string]interface{} {
 	}
 }
 
-func (h *headsetScanNode) Close() error { return nil }
+func (h *headsetScanNode) Close() error {
+	return h.fetcher.Close()
+}
 
 func (h *headsetScanNode) Source() planNode { return nil }