Re: ElasticSearch adapter. Exposing meta fields (like _id, _uid etc.)
Can somebody pls take a look at the following PR:
Specifically, I would like to understand if adding explicit mapping
between expression (`EXPR$n`) and item (`_MAP['foo.bar']`) is a correct
(and recommended) approach. The reason I need it is because the original
item name (eg. `_MAP['foo.bar']`) is lost after converter operation (ie I'm
not able to derive it from `input.getRowType()`)
-- Here I get EXPR$0 and EXPR$1 but no information about 'id' and 'foo.bar'
select _MAP['_id'], _MAP['foo.bar'] from elastic
-- Query below preserves attribute information
select * from (select _MAP['_id'] as \"_id\", _MAP['foo.bar'] as
\"foo.bar\" from elastic)
On Sat, Dec 22, 2018 at 3:11 AM Stamatis Zampetakis <zabetak@xxxxxxxxx>
> Hi Andrei,
> Many data management systems have internal columns which the users may be
> able to query (see for example Postgres ). It doesn't sound unnatural to
> allow users access these fields. On the other hand such system columns do
> not appear in SELECT * queries and I suppose they are pruned out by
> projections early on if they are not used by the query. I guess you could
> take a similar approach in the ElasticSearch adapter.
>  https://www.postgresql.org/docs/current/ddl-system-columns.html
> Στις Σάβ, 22 Δεκ 2018 στις 1:14 π.μ., ο/η Andrei Sereda <andrei@xxxxxxxxx>
> > Hello,
> > Upon indexing, elastic allocates a unique _id
> > <
> > >
> > 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
> > <
> > >
> > ).
> > 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.