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https://issues.apache.org/jira/browse/SOLR-236?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12749464#action_12749464
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Martijn van Groningen commented on SOLR-236:
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Hi Thomas, currently both collapsing algorithms do not store the the ids of the
collapsed documents.
In order to have this functionality I think the following has to be done:
1) In the doCollapsing(...) methods of both concrete implementations of
DocumentCollapser, the collapsed documents have to be stored. Depending on what
you want you can store it in one big list or store it a list per most relevant
document. The most relevant document is the document that does *not* collapse.
2) In the getCollapseInfo(...) method in the AbstractDocumentCollapser you then
need to output these collapsed documents. If you are storing the collapsed
documents in one big list then adding a new NamedList with collapsed document
would be fine I guess. If you are storing the collapsed documents per document
head, then I would add the collapsed document ids to existing resDoc named
list. It is important that you return the Solr unique id instead of the lucene
id.
This is just one approach, but what is the reason that you want this
functionality? I guess what would be much easier, is to do a second query after
the collapse query. In this second query you disable field collapsing (by not
setting collapse.field) and you set fq=[collapse.field]=[collapse.value] for
example.
Potentially the number of collapsed documents can be very large and in that
situation it can have a impact on performance. Therefore I think that this
functionality should be disabled by default. In the same way collapseInfoDoc
and collapseInfoCount are managed.
> Field collapsing
> ----------------
>
> Key: SOLR-236
> URL: https://issues.apache.org/jira/browse/SOLR-236
> Project: Solr
> Issue Type: New Feature
> Components: search
> Affects Versions: 1.3
> Reporter: Emmanuel Keller
> Fix For: 1.5
>
> Attachments: collapsing-patch-to-1.3.0-dieter.patch,
> collapsing-patch-to-1.3.0-ivan.patch, collapsing-patch-to-1.3.0-ivan_2.patch,
> collapsing-patch-to-1.3.0-ivan_3.patch, field-collapse-3.patch,
> field-collapse-4-with-solrj.patch, field-collapse-5.patch,
> field-collapse-solr-236-2.patch, field-collapse-solr-236.patch,
> field-collapsing-extended-592129.patch, field_collapsing_1.1.0.patch,
> field_collapsing_1.3.patch, field_collapsing_dsteigerwald.diff,
> field_collapsing_dsteigerwald.diff, field_collapsing_dsteigerwald.diff,
> SOLR-236-FieldCollapsing.patch, SOLR-236-FieldCollapsing.patch,
> SOLR-236-FieldCollapsing.patch, solr-236.patch, SOLR-236_collapsing.patch,
> SOLR-236_collapsing.patch
>
>
> This patch include a new feature called "Field collapsing".
> "Used in order to collapse a group of results with similar value for a given
> field to a single entry in the result set. Site collapsing is a special case
> of this, where all results for a given web site is collapsed into one or two
> entries in the result set, typically with an associated "more documents from
> this site" link. See also Duplicate detection."
> http://www.fastsearch.com/glossary.aspx?m=48&amid=299
> The implementation add 3 new query parameters (SolrParams):
> "collapse.field" to choose the field used to group results
> "collapse.type" normal (default value) or adjacent
> "collapse.max" to select how many continuous results are allowed before
> collapsing
> TODO (in progress):
> - More documentation (on source code)
> - Test cases
> Two patches:
> - "field_collapsing.patch" for current development version
> - "field_collapsing_1.1.0.patch" for Solr-1.1.0
> P.S.: Feedback and misspelling correction are welcome ;-)
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