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From "Yonik Seeley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (SOLR-236) Field collapsing
Date Tue, 22 Dec 2009 14:08:29 GMT

    [ https://issues.apache.org/jira/browse/SOLR-236?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12793621#action_12793621
] 

Yonik Seeley commented on SOLR-236:
-----------------------------------

bq. As far as I understand from your collapse algorithm proposal, in order to save memory
you'd like to restrict the group creation to only those that belong in the requested results
page.

A ton of memory, and probably a good amount of time too.  It may be the only variant that
certain people would be able to use (but note that it is just a variant - I'm not proposing
doing away with the other options).

bq. I think there might be a problem with pagination as well

Yes, pagination is a sticky issue... but I don't think this algorithm messes it up further.

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?  I guess they over-request
a little.  What if they want a fixed number of groups?  I guess they over-request by a lot
(nGroups*collapse.threshold).  Then they need to keep track of how many documents they actually
used.

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).

> 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_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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