Hello,
Upon indexing, elastic allocates a unique _id
<https://www.elastic.co/guide/en/elasticsearch/reference/current/mapping-id-field.html>
for each document (unless specified by the user). Currently when mapping
between elastic result and calcite return type we query only _source or
fields attributes. _id is not part those but exposed at higher level in
query response (see SearchHit
<https://www.elastic.co/guide/en/elasticsearch/reference/6.1/_the_search_api.html>
).
Currently _MAP['foo'] becomes _source.get('foo') (or fields.get('foo')).
Do you think we should make _MAP['_id'] available implicitly ?
I have a couple of use-cases where one needs to know document ID.
Please note this makes sense only for non-aggregate queries.
Regards,
Andrei.
