<p dir="auto">Currently it is impossible to access owner's fields from a nested aggregation. So it is not possible to do following:</p>
<ul dir="auto">
<li>Bucket aggregations on them (a very common use case) as a sub aggregation of  the nested one. For example If multiple lawyers are assigned to cases of different types and each assignment captures his/her hours spent and report needs to be total hours by lawyer by case type. It is impossible to do so. Using reverse_nested and back will not produce desired results</li>
<li>Filter on owner's fields within aggregations.</li>
<li>Metrics aggregations on owner's fields are a little less useful as there will be double-counting but often are necessary as well</li>
</ul>
<p dir="auto">Currently it is impossible to access owner's fields from a nested aggregation. So it is not possible to do following:</p>
<ul dir="auto">
<li>Bucket aggregations on them (a very common use case) as a sub aggregation of  the nested one. For example If multiple lawyers are assigned to cases of different types and each assignment captures his/her hours spent and report needs to be total hours by lawyer by case type. It is impossible to do so. Using reverse_nested and back will not produce desired results</li>
<li>Filter on owner's fields within aggregations.</li>
<li>Metrics aggregations on owner's fields are a little less useful as there will be double-counting but often are necessary as well</li>
</ul>