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From "Michael McCandless (JIRA)" <>
Subject [jira] [Commented] (SOLR-2524) Adding grouping to Solr 3x
Date Sun, 29 May 2011 12:45:47 GMT


Michael McCandless commented on SOLR-2524:

bq. I was using this patch last week and didn't encounter problems.

Excellent -- thank you for testing :)

bq. Why is it actually blocked by LUCENE-3099, vs. merely stands to benefit from improvements
there when it happens?

Well... Hoss is (rightly) nervous that we have divergent grouping
impls in trunk vs 3.x.

There are non-trivial differences... 3.x improves on trunk's impl:

  * Optionally uses CachingCollector, so certain queries will be
    substantially faster (adds new request param

  * Optionally it's able to get total count of number of unique
    groups (using AllGroupsCollector).

But, also, 3.x uses way more RAM than trunk's impl when grouping by a
non-term field, because the grouping module currently always pulls a
StringIndex (but LUCENE-3099 will fix this!).

Hoss also wanted to see all of Solr trunk's grouping tests backported,
and that is now done (thanks Martijn).

We could simply commit anyway, for 3.3, on the strong expectation that
we are going to cut trunk over to the grouping module before shipping
4.0...?  Any objections?  This way 3.3 will have grouping, and we let
the feature "bake" on Jenkins daily testing instead of aging as a patch...

> Adding grouping to Solr 3x
> --------------------------
>                 Key: SOLR-2524
>                 URL:
>             Project: Solr
>          Issue Type: New Feature
>            Reporter: Martijn van Groningen
>            Assignee: Michael McCandless
>             Fix For: 3.3
>         Attachments: SOLR-2524.patch, SOLR-2524.patch, SOLR-2524.patch, SOLR-2524.patch,
> Grouping was recently added to Lucene 3x. See LUCENE-1421 for more information.
> I think it would be nice if we expose this functionality also to the Solr users that
are bound to a 3.x version.
> The grouping feature added to Lucene is currently a subset of the functionality that
Solr 4.0-trunk offers. Mainly it doesn't support grouping by function / query.
> The work involved getting the grouping contrib to work on Solr 3x is acceptable. I have
it more or less running here. It supports the response format and request parameters (expect:
group.query and group.func) described in the FieldCollapse page on the Solr wiki.
> I think it would be great if this is included in the Solr 3.2 release. Many people are
using grouping as patch now and this would help them a lot. Any thoughts?

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