Hi I am getting the following error while trying to create/merge nodes and relationships. It does not always happens but it occurs once in a while.

> 
> CypherError: An unexpected failure occurred, see details in the
>  database logs, reference number eaf50bff-deca-4055-9450-6a76c31534e4.
> 
> 
> 

This is the traceback:

```
---------------------------------------------------------------------------
CypherError                               Traceback (most recent call last)
<ipython-input-21-9700f3a5d3fa> in <module>()
      7     tx.success = True
      8     #tx.close()
----> 9   session.close()

/databricks/python/local/lib/python2.7/site-packages/neo4j/v1/session.pyc in close(self)
    522         """
    523         if self.last_result:
--> 524             self.last_result.buffer()
    525         if self.transaction:
    526             self.transaction.close()

/databricks/python/local/lib/python2.7/site-packages/neo4j/v1/session.pyc in buffer(self)
    246         if self.connection and not self.connection.closed:
    247             while not self._consumed:
--> 248                 self.connection.fetch()
    249             self.connection = None
    250

```

My code for create/merge is this:

```
for chunk in chunk_list: 
  with session.begin_transaction() as tx:
    for record in chunk:
      tx.run("MERGE (source:UID {userid : {m}, timestamp: {a}})"
             "MERGE (target:UID {userid : {n}, timestamp: {a}})"
             "MERGE (source)-[:HasConnection]-(target)", {"m": record.source, "n": record.target, "a": record.unix_timestamp_s})
    tx.success = True
    #tx.close()
  session.close()

```

chunk\_list is a list containing multiple lists of records. Each of the list within chunk\_list has multiple rows (approx 10000) and each row contains three columns, source, target and timestamp. 

For each list within chunk\_list we are opening a session then doing the merge operations and then closing the session.

The problem starts to happen when the graph exceeding more than 10 million nodes. Lets say for Day 1 the chunk\_list has 4 million rows, it would work fine, for Day 2 if the chunk\_list has 4 million rows it would work fine as well. But if on Day 3 there are 3 million rows and the total number of nodes is more than 10 million overall in the Neo4j graph then the problem starts to happen.