boto3 get_query_runtime_statistics sometimes not returning "rows" data

I have a lambda that attempts to find out whether a previously executed athena query has returned any rows or not. To do so I am using the boto3 function get_query_runtime_statistics and then extracting the "Rows" data:

response = athena_client.get_query_runtime_statistics(QueryExecutionId=query_id)

row_count = response["QueryRuntimeStatistics"]["Rows"]["OutputRows"]

However, in a previous execution the response object has not contained the "Rows" data, resulting in a KeyError being thrown. I know I can get around the KeyError by using .get("Rows", {}).get("OutputRows") etc.

I reran the exact same query in the athena console (it returns 0 rows) and then used the query ID to get the runtime statistics of this duplicate query execution. This time it had the "Rows" data in the response. Therefore the behaviour doesn’t appear to be consistent for a given query string; however, if I get the statistics for the original query execution the response consistently does not contain the "Rows" data.

What I want to know is whether every time "Rows" data is not present can I assume that the output row count was zero?

I couldn’t find anything in the AWS docs explaining why "Rows" may not always be present in the API response.

Thanks 🙂

PS. If you don’t want to follow the link to the documentation, here is the response schema according to boto3:

{
    'QueryRuntimeStatistics': {
        'Timeline': {
            'QueryQueueTimeInMillis': 123,
            'QueryPlanningTimeInMillis': 123,
            'EngineExecutionTimeInMillis': 123,
            'ServiceProcessingTimeInMillis': 123,
            'TotalExecutionTimeInMillis': 123
        },
        'Rows': {
            'InputRows': 123,
            'InputBytes': 123,
            'OutputBytes': 123,
            'OutputRows': 123
        },
        'OutputStage': {
            'StageId': 123,
            'State': 'string',
            'OutputBytes': 123,
            'OutputRows': 123,
            'InputBytes': 123,
            'InputRows': 123,
            'ExecutionTime': 123,
            'QueryStagePlan': {
                'Name': 'string',
                'Identifier': 'string',
                'Children': [
                    {'... recursive ...'},
                ],
                'RemoteSources': [
                    'string',
                ]
            },
            'SubStages': [
                {'... recursive ...'},
            ]
        }
    }
}