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From "Michael McCandless (Commented) (JIRA)" <>
Subject [jira] [Commented] (LUCENE-3778) Create a grouping convenience class
Date Wed, 15 Feb 2012 15:55:03 GMT


Michael McCandless commented on LUCENE-3778:

This sounds like a good idea!  Grouping is hard to use now...

Would it be something like this?

GroupSearch ctx = new GroupingSearch(groupByField);


topGroups =, query, numGroups);

... and the search method figures out which first/second pass
collectors to make, whether to cache, etc.?

Would you also handle block (single pass) grouping with the same

I guess you'd then .getAllGroups(), .getAllGroupHeads() after

Hmm would we try to handle Term/BytesRef and Function/MutableValue
with the same class?

> Create a grouping convenience class
> -----------------------------------
>                 Key: LUCENE-3778
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: modules/grouping
>            Reporter: Martijn van Groningen
> Currently the grouping module has many collector classes with a lot of different options
per class. I think it would be a good idea to have a GroupUtil (Or another name?) convenience
class. I think this could be a builder, because of the many options (sort,sortWithinGroup,groupOffset,groupCount
and more) and implementations (term/dv/function) grouping has.

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