Re: [hibernate-dev] [Search] supporting DISTINCT (or similar) for values
2011/8/24 Hardy Ferentschik <hardy(a)hibernate.org>:
On Wed, 24 Aug 2011 10:36:39 +0200, Sanne Grinovero
<sanne(a)hibernate.org>
wrote:
> This was asked some times, and today a new interesting use case was
> proposed on the forums:
> https://forum.hibernate.org/viewtopic.php?f=9&t=1012360
>
> I usually tell the whole story "distinct is not fit for fulltext...
> use the relational queries"
I've seen the post and answered saying pretty much what you just said.
> but since it's often requested (on
> Infinispan Query too) and I just realized that in fact we could
> implement it as the needed information is in the index, and we could
> efficiently extract it and wrap in a nice and easy API.
As I see it, it is a special case of projection. Maybe there could be an
additional option to the 'setProjection' call.
Btw, how is this information available?
From the IndexReader you can iterate a specific field's values;
that's
how faceting is built and why I think the forum poster was mentioning
faceting;
the faceting field works very similarly to a "distinct" selection on the term.
> Shall I open a JIRA for this? Likely for 4.1 I would say, for now I'm
> just collecting opinion if we should support this, and if somebody has
> an idea of how such an API should look like.
I think it is worth an issue, since it is a very typical usecase.
Ok, this is HSEARCH-868 then.
--Hardy
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