[
https://issues.apache.org/jira/browse/SOLR-236?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12717110#action_12717110
]
Earwin Burrfoot commented on SOLR-236:
--------------------------------------
I have implemented collapsing on a high-volume project of mine in much less
flexible, but more practical manner.
Part I. You have to guarantee that all documents having the same value of
collapse-field are dropped into Lucene index as a sequential batch. That
guarantees they get sequential docIds, and with some more work - that they all
end up in the same segment.
Part II. When doing collection you always get docIds in sequential order, and
thus, thanks to Part I you get the docs-to-be-collapsed already grouped by
collapse-field, even before you drop the docs into PriorityQueue to sort them.
Cons:
You can only collapse on a single predetermined at index creation time field.
If one document changes, you have to reindex all docs that have the same
collapse-field value, so it's best if you have either low update/add rates, or
few documents sharing the same collapse-field value.
Pros:
The CPU and memory costs for collapsing compared to usual search are very close
to zero and do not depend on index size/total docs found.
The same idea works with new Lucene per-segment collection and in distributed
mode (sharded index).
Within collapsed group you can sort hits however you want, and select one that
will represent the group for usual sort/paging.
The implementation is not brain-dead simple, but nears it.
> 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-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 ;-)
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
