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From "Chris Male (Commented) (JIRA)" <>
Subject [jira] [Commented] (LUCENE-3482) Refactor grouping module to be more maintainable
Date Mon, 03 Oct 2011 01:24:33 GMT


Chris Male commented on LUCENE-3482:

I really have to echo Yonik's concerns here.  If we provide too much abstraction and indirection
in the code then you're going to see a performance decrease just from method call overhead.
 This is especially so if the ValueSources contain multiple layers.
> Refactor grouping module to be more maintainable
> ------------------------------------------------
>                 Key: LUCENE-3482
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: modules/grouping
>    Affects Versions: 4.0
>            Reporter: Martijn van Groningen
>             Fix For: 4.0
>         Attachments: LUCENE-3482.patch
> Currently we have 4 types of grouping collectors and 8 concrete subclasses in Lucene
/ Solr. In current architecture for each type of collector two concrete subclasses need to
be created. An implementation optimized for single term based groups and a more general implementation
that works with MutableValue to also support grouping by functions. If we want for example
group by IndexDocValues each type of grouping collector needs to have three concrete subclasses.
This design isn't very maintainable.
> I think it is best to introduce a concept that knows how deals with dealing groups for
all the different sources. Therefore the grouping module should depend on the queries module,
so that grouping can reuse the ValueSource concept. A term based concrete impl. of this concept
knows for example to use the DocValues.ord() method. Or more generic concrete impl. will use

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