Description of problem:

$ java -jar target/migrator-executable/data-migrator-4.8.0-SNAPSHOT.jar   --cassandra-port=9142
Estimation process - starting

java.lang.NullPointerException
	at org.rhq.server.metrics.migrator.workers.MetricsIndexUpdateAccumulator.getLastAggregationTime(MetricsIndexUpdateAccumulator.java:158)
	at org.rhq.server.metrics.migrator.workers.MetricsIndexUpdateAccumulator.<init>(MetricsIndexUpdateAccumulator.java:77)


This happens when e.g. the 1h (and probably the 6h) table has no data in it.

Problem is in


org.rhq.server.metrics.migrator.workers.MetricsIndexUpdateAccumulator#getLastAggregationTime
[...]
        if (duration != null && queryString != null) {
            Query query = session.createSQLQuery(queryString);
            String queryResult = query.uniqueResult().toString();

Here query.uniqueResult() can be null if no data is present