[hibernate-dev] Support for Elasticsearch in Hibernate OGM proposal

[Gunnar Morling]

2014-08-22 14:01 GMT+02:00 Emmanuel Bernard <emmanuel at hibernate.org>:

>
> On 22 Aug 2014, at 10:34, Jiri Holusa <jholusa at redhat.com> wrote:
>
> An alternative which may be a bit simpler and give quicker success for
> simplistic queries would be to implement an ES backend of our pluggable
> HQL/JP-QL parser. We already have implementations of this which take HQL
> queries and translate them into corresponding MongoDB/Neo4j queries, so the
> same should be doable for ES. But this wouldn't really carry semantics of
> full-text queries (fuzzy search etc.) as one could get it via HSearch and
> might expect for a backend such as ES.
>
>
> Hmm, first approach seems to me a better way to do it, but as you said,
> HSearch has to be
> "undependent" on Lucene first. So I will start with CRUD and see where I
> can get. Maybe
> after that, something around HSearch and Lucene will be resolved, so than
> I could decide
> whick approarch to use.
>
>
> Gunnar, the direct HQL->ES-QL work is not as trivial as it seems. I don’t
> think ElasticSearch can search on fields that are not explicitly indexed.
> (Jiri correct me if I’m wrong). So we would need to guess or anticipate
> which field wants to be indexed and how “transparently”. Not the best of
> settings.
>

Interesting, I really need to take a closer look at ES and its APIs.

How does it react when searching on an un-indexed field? If we can detect
the situation and raise a meaningful exception indicating that an index is
missing so a given query can't be run (could even be done during start-up
for named queries), then I'd say that's good enough, at least for a first
iteration? In particular if we add support for @Index so a user can react.
As said that solution would only be a work-around until we can delegate
that task to HSearch (which then would have the same challenge probably).

Btw. it's the same with Cassandra apparently, you also need to index
up-front the columns targeted in queries.

--Gunnar