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From Martijn v Groningen <>
Subject Re: Stats per group with StatsComponent?
Date Sat, 03 Dec 2011 09:50:25 GMT
Hi Morten,

You can also take a look at:

That is also a second pass collector. It collects all unique terms for
a specified field for all top N groups.
This is just the Lucene side. After it is committed it also needs be
wired up in Solr.


On 2 December 2011 11:46, Martijn v Groningen
<> wrote:
> Hi Morten,
>> As far as I understand, I need to create a subclass of
>> AbstractSecondPassGroupingCollector, and for each group maintain some sort
>> of structure to hold on to my values.
> This class is meant for collecting top N documents inside a group. The
> reason it is abstract is because it can get its group values from
> different source like indexed terms, function results and indexed
> docvalues.
> I think there should be a new collector type for computing min / max.
> This is also a second pass collector b/c it depends on the top
> SearchGroups collected by a concrete impl of
> AbstractFirstPassGroupingCollector.
>> As to getting the values, I think I understand how it works, but if anyone
>> could point me towards some documentation about how the AtomicReaderContext
>> works, and how to read specific fields, that would be great.
> Well there is the javadoc :) but what is important to remember that
> all the grouping collectors work per segment. It needs the
> AtomicReaderContext to get the values to do grouping for each segment.
>> My biggest question at the moment is how to get my values into the response?
>> I was thinking I should create an new Grouping.Command that did this, but
>> then it seems I can't include the values directly with each group (the lists
>> in the "groups" element), but would need to add a separate structure with
>> the values for each group. Am I right in that assumption? How can I add more
>> values to the lists in the "groups" element? Which behavior would be
>> preferred?
>> I was hoping to end up with a response that looks sort of like the attached
>> XML.
> I also think the statistics section should included in each group like
> in your attached response example.
> If the Grouping.Command class gets a new method getStatsCollector()
> which returns zero or more collectors.
> Each of this collector is executed in the second search, then in the
> addDocList method the result of each collector can
> be put in the response.
> Martijn

Met vriendelijke groet,

Martijn van Groningen

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