[orientdb] added known issues to README

orientdb/README.md

@@ -23,7 +23,7 @@ This section describes how to run YCSB on OrientDB running locally.
 
 Clone the YCSB git repository and compile:
 
-    git clone git://github.com/nuvolabase/YCSB.git
+    git clone https://github.com/brianfrankcooper/YCSB.git
     cd YCSB
     mvn clean package
 
@@ -46,3 +46,8 @@ See the next section for the list of configuration parameters for OrientDB.
 ### `OrientDB.user` (default `admin`)
 
 ### `OrientDB.password` (default `admin`)
+
+## Known Issues
+
+* There is a performance issue around the scan operation. This binding uses OIndex.iterateEntriesMajor() which will return unnecessarily large iterators. This has a performance impact as the recordcount goes up. There are ideas in the works to fix it, track it here: [#568](https://github.com/brianfrankcooper/YCSB/issues/568).
+* The OIndexCursor used to run the scan operation currently seems to be broken. Because of this, if the startkey and recordcount combination on a particular operation were to cause the iterator to go to the end, a NullPointerException is thrown. With sufficiently high record counts, this does not happen very often, but it could cause false negatives. Track that issue here: https://github.com/orientechnologies/orientdb/issues/5541.