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From: Itamar Syn-Hershko <itamar@code972.com>
Date: Wed, 9 Nov 2016 19:17:25 -0800
Message-ID: <CAHTr4Zt52BXi2uRMAz68PZuPw87QknC4kaq1Rso3wXdKMGGvRQ@mail.gmail.com>
Subject: Re: TermDistinctValuesCollector
To: user@lucenenet.apache.org
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archived-at: Thu, 10 Nov 2016 03:17:49 -0000

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The Java docs have it explained nicely

https://lucene.apache.org/core/4_8_1/grouping/org/apache/lucene/search/grouping/package-summary.html

--

Itamar Syn-Hershko
http://code972.com | @synhershko <https://twitter.com/synhershko>
Freelance Developer & Consultant
Lucene.NET committer and PMC member

On Tue, Nov 8, 2016 at 12:12 AM, Shad Storhaug <shad@shadstorhaug.com>
wrote:

> Hi Julian,
>
> Just to be sure we are on the same page, the grouping functionality was
> posted as a pull request mere hours ago https://github.com/apache/
> lucenenet/pull/193. This doesn't yet exist in the master branch or on
> NuGet. But since most of these types are missing from the master branch and
> it sounds like you are compiling fine, you are probably on the right page
> (just need to check). If not, you should pull down that branch and compile
> it.
>
> I can't tell you exactly how the functionality works, but I can point you
> to the tests. Unfortunately, the tests are very complex and there are not
> many of them so I am not sure how helpful they will be. At least they will
> give you some idea of what is required for a common grouping scenario. The
> test are at: https://github.com/NightOwl888/lucenenet/tree/
> grouping/src/Lucene.Net.Tests.Grouping.
>
>
> Perhaps someone else can give you some better insight on how the
> functionality works - you might want to try the Lucene (Java) user group if
> you are having trouble finding detailed documentation. The API is very
> similar in .NET.
>
> Thanks,
> Shad Storhaug (NightOwl888)
>
> -----Original Message-----
> From: Julian Ohrt [mailto:julian.ohrt@aploris.com]
> Sent: Tuesday, November 8, 2016 2:43 PM
> To: user@lucenenet.apache.org
> Subject: TermDistinctValuesCollector
>
> Hi:
>
> I am trying to use the class TermDistinctValuesCollector from Core
> namespace Lucene.Net.Search.Grouping.
> Studying http://www.solr-start.com/javadoc/solr-lucene/org/
> apache/lucene/search/grouping/term/TermDistinctValuesCollector.html
> I found a short explanation for the three parameters of the constructor:
>
> groupField - The field to group by
> countField - The field to count distinct values for groups - The top N
> groups, collected during the first phase search
>
> I am still not sure what the group is (is it the field for which the
> content is counted?), why a lucene field is needed for counting, and what
> the "first phase search" is.
> I tried something like this:
>
> Collection<GroupCount> groups = new Collection<GroupCount>();
> TermDistinctValuesCollector collector = new TermDistinctValuesCollector("groupField",
> "countField", groups); mIndexSearcher.Search(query, null, collector);
>
> Of course to no avail. Groups is empty. It did give me any result at all.
>
> Is there any documentation I missed? I did not even find any second hit
> for "TermDistinctValuesCollector" in the lucenenet repository except for
> TermDistinctValuesCollector.cs itself. Not even a unit test.
>
> A short example how to use it would be awesome. But I'd also like to
> understand how it works (should work) internally. What are member variables
> ordSet, groupFieldTermIndex, etc. used for? Not knowing the internals of
> lucene I just don't understand the source code.
>
> Thanks a lot!
> Julian
>
>
>

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