[jira] Commented: (SOLR-236) Field collapsing

["Leon Messerschmidt (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-236?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12839545#action_12839545 ] 

Leon Messerschmidt commented on SOLR-236:
-----------------------------------------

The OutOfMemory problem affects both field-collapse-5.patch on Solr 1.4 and SOLR-236.patch on the trunk.

The root cause of the problem is DocSetScoreCollector that creates an array of float that is the size of the maxID document that matches the query.  If you have a large index (we have several million documents) and a document with a very large id is matched you may end up with a huge array (in our case several hundred MB).  Only a really small subset of the array is being used at any given time (especially if you're matching just a few documents with big doc ids).  

The implementation can rather use a sparse array or a map to keep track of scores.

> 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.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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