presto-thrift/src/main/java/io/prestosql/plugin/thrift/ThriftIndexPageSource.java/ThriftIndexPageSource/startDataFetchForNextSplit
class ThriftIndexPageSource:    private void startDataFetchForNextSplit()
    {
        PrestoThriftSplit split = splits.get(splitIndex);
        splitIndex++;
        RunningSplitContext context = new RunningSplitContext(openClient(split), split);
        sendDataRequest(context, null);
    }