Problem: unhandled error when storing zero utxo

Solution: only execute the query if *unspent_outputs is not empty

bigchaindb/backend/localmongodb/query.py

@@ -228,13 +228,17 @@ def delete_transactions(conn, txn_ids):
 
 @register_query(LocalMongoDBConnection)
 def store_unspent_outputs(conn, *unspent_outputs):
-    try:
-        return conn.run(
-            conn.collection('utxos')
-            .insert_many(unspent_outputs, ordered=False))
-    except DuplicateKeyError:
-        # TODO log warning at least
-        pass
+    if unspent_outputs:
+        try:
+            return conn.run(
+                conn.collection('utxos').insert_many(
+                    unspent_outputs,
+                    ordered=False,
+                )
+            )
+        except DuplicateKeyError:
+            # TODO log warning at least
+            pass
 
 
 @register_query(LocalMongoDBConnection)

tests/backend/localmongodb/test_queries.py

@@ -240,6 +240,13 @@ def test_delete_unspent_outputs(db_context, utxoset):
             {'transaction_id': 'a', 'output_index': 1}).count() == 1
 
 
+def test_store_zero_unspent_output(db_context, utxo_collection):
+    from bigchaindb.backend import query
+    res = query.store_unspent_outputs(db_context.conn)
+    assert res is None
+    assert utxo_collection.count() == 0
+
+
 def test_store_one_unspent_output(db_context,
                                   unspent_output_1, utxo_collection):
     from bigchaindb.backend import query