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From "Martijn van Groningen (Commented) (JIRA)" <>
Subject [jira] [Commented] (LUCENE-3778) Create a grouping convenience class
Date Mon, 05 Mar 2012 14:35:57 GMT


Martijn van Groningen commented on LUCENE-3778:

One can actually use GroupingSearch in a shard'd env, on each shard,
right? It's just that then you merge them like normal on the front
end (ie, TopGroups.merge). Is that the only reason for the "... in a
non distributed environment" javadoc warning?
In a sharded env one needs to first execute all the first pass collector on all shards, merge
the returned search groups, execute the second pass search (with the top N merged search groups
as argument) on most of the shards and finally merge the TopGroups from all shards into a
topN TopGroups. Also grouping by docblock and grouping features like allGroups and groupHead
don't work in a normal sharded environment (unless you partition the groups properly). The
docs caching also only makes sense when performing grouping on a local index. This usage is
very different then non distributed grouping, that is why I think it is better to have a separate
grouping convenience class for distributed grouping (DistributedGroupSearch?). 

bq. Maybe the ctor should take docValuesType / diskResidentValues
Makes sense!

bq. Maybe you should pass the groupSort, groupsOffset, groupsLimit to the search method (instead
of setters)?
Maybe we just should have defaults for these options? Sort.RELEVANCE, 0 and 10?
> Create a grouping convenience class
> -----------------------------------
>                 Key: LUCENE-3778
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: modules/grouping
>            Reporter: Martijn van Groningen
>         Attachments: LUCENE-3778.patch
> 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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