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https://issues.apache.org/jira/browse/SOLR-236?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12794252#action_12794252
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Uri Boness commented on SOLR-236:
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{quote}If we are returning a number of documents (as opposed to a number of
groups) to the user, how do they avoid splitting on a page in the middle of the
group?{quote}
As far as I know (Martijn, correct me if I'm wrong), Martijn's patch returns
the number of groups *and* documents, where each group is actually represented
as a document. So in that sense, the total count applies to the result set as
is (groups count as documents) and therefore pagination just works.
{quote}The only thing this algorithm can't do (related to pagination) is give
the total number of documents after collapsing (and hence can't calculate the
exact number of pages). This can be fine in many circumstances as long as the
gui handles it (people don't seem to mind google doing it... I just tried it.
Google didn't show the result count right unless displaying the last
page).{quote}
First of all, I must admit that I never noticed that in Google, so I guess
you're right :-). But when you think about it, with Google, how many time do
you get a low hit count that only fits in 2-3 pages? Well, I hardly ever get
it, and when I do I don't even bother to check the result I just try to improve
my search. With Solr, a lot of times its different, specially when all these
discovery features and faceting are so often used to narrow the search
extensively... I'm not saying not having a perfect pagination mechanism is a
problem... not at all, I'm just saying that it *might* be an issue for specific
use cases or specific domains.... but that's just an assumption (or a gut
feeling) :-)
> 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
> Assignee: Shalin Shekhar Mangar
> 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-5.patch, field-collapse-5.patch, field-collapse-5.patch,
> field-collapse-5.patch, field-collapse-5.patch, field-collapse-5.patch,
> field-collapse-5.patch, field-collapse-5.patch, field-collapse-5.patch,
> field-collapse-5.patch, field-collapse-5.patch, field-collapse-5.patch,
> field-collapse-5.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,
> quasidistributed.additional.patch, SOLR-236-FieldCollapsing.patch,
> SOLR-236-FieldCollapsing.patch, SOLR-236-FieldCollapsing.patch,
> SOLR-236.patch, SOLR-236.patch, SOLR-236.patch, SOLR-236.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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