Here is a sample script which accesses a DataRow

var ds = server.ExecuteDataSet(context.connectionString, context.queryText, context);

var dt = ds.Tables(0);
var drs = dt.Rows;

for(var i = 0; i < drs.Count; i++) {
    var dr = drs(i);
    var value = dr(0);
    logger.LogMessage(MessageType.Information, value, "");
}

The line value = dr(0) cause OperationCanceledException which is caught internally. However, this causes a big performance issue in the loop. The issue is in TypeHelpers.cs in the source code of ClearScript:

if (argIndex >= args.Length)
{
    if (!param.IsOptional && !param.HasDefaultValue)
    {
        throw new OperationCanceledException();
    }

    continue;
}

The same issue does not occur in 7.3.1.