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Posted to dev@lucene.apache.org by "Michael McCandless (JIRA)" <ji...@apache.org> on 2011/05/14 18:22:47 UTC

[jira] [Commented] (LUCENE-3097) Post grouping faceting

    [ https://issues.apache.org/jira/browse/LUCENE-3097?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13033575#comment-13033575 ] 

Michael McCandless commented on LUCENE-3097:
--------------------------------------------

bq. If we group by hotel and have a facet for airport. Most end users expect (according to my experience off course) the following airport facet:

+1, I think that semantics is intuitive.  It treats each group as a doc w/ multi-valued field whose values are unioned from all docs within it.  So group "Hotel a" has values AMS, DUS for the departure_airport field.

> Post grouping faceting
> ----------------------
>
>                 Key: LUCENE-3097
>                 URL: https://issues.apache.org/jira/browse/LUCENE-3097
>             Project: Lucene - Java
>          Issue Type: New Feature
>            Reporter: Martijn van Groningen
>            Priority: Minor
>             Fix For: 3.2, 4.0
>
>
> This issues focuses on implementing post grouping faceting.
> * How to handle multivalued fields. What field value to show with the facet.
> * Where the facet counts should be based on
> ** Facet counts can be based on the normal documents. Ungrouped counts. 
> ** Facet counts can be based on the groups. Grouped counts.
> ** Facet counts can be based on the combination of group value and facet value. Matrix counts.   
> And properly more implementation options.
> The first two methods are implemented in the SOLR-236 patch. For the first option it calculates a DocSet based on the individual documents from the query result. For the second option it calculates a DocSet for all the most relevant documents of a group. Once the DocSet is computed the FacetComponent and StatsComponent use one the DocSet to create facets and statistics.  
> This last one is a bit more complex. I think it is best explained with an example. Lets say we search on travel offers:
> |||hotel||departure_airport||duration||
> |Hotel a|AMS|5
> |Hotel a|DUS|10
> |Hotel b|AMS|5
> |Hotel b|AMS|10
> If we group by hotel and have a facet for airport. Most end users expect (according to my experience off course) the following airport facet:
> AMS: 2
> DUS: 1
> The above result can't be achieved by the first two methods. You either get counts AMS:3 and DUS:1 or 1 for both airports.

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