pseudo-field-collapsing
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Key: SOLR-1311
URL: https://issues.apache.org/jira/browse/SOLR-1311
Project: Solr
Issue Type: New Feature
Components: search
Affects Versions: 1.4
Reporter: Marc Sturlese
Fix For: 1.5
I am trying to develope a new way of doing field collapsing based on the
adjacent field collapsing algorithm. I have started developing it beacuse I am
experiencing performance problems with the field collapsing patch with big
index (8G).
The algorith does adjacent-pseudo-field collapsing. It does collapsing on the
first X documents. Instead of making the collapsed docs disapear, the algorith
will send them to a given position of the relevance results list.
The reason I just do collapsing in the first X documents is that if I have for
example 600000 results and I am showing 10 results per page, I really don't
need to do collapsing in the page 30000 or even not in the 3000. Doing this I
am noticing dramatically better performance. The problem is I couldn't find a
way to plug the algorithm as a component and keep good performance. I had to
hack few classes in SolrIndexSearcher.java
This patch is just experimental and for testing purposes. In case someone finds
it interesting would be good do find a way to integrate it in a better way than
it is at the moment.
Advices are more than welcome.
Functionality:
In solrconfig.xml we specify the pseudo-collapsing parameters:
<str name="plus.considerMoreDocs">true</str>
<str name="plus.considerHowMany">3000</str>
<str name="plus.considerField">name</str>
(at the moment there's no threshold and other parameters that exist in the
current collapse-field patch)
plus.considerMoreDocs one enables pseudo-collapsing
plus.considerHowMany sets the number of resultant documents in wich we want to
apply the algorithm
plus.considerField is the field to do pseudo-collapsing
If the number of results is lower than plus.considerHowMany the algorithm will
be applyed to all the results.
Let's say there is a query with 600000 results and we've set considerHowMany to
3000 (and we already have the docs sorted by relevance).
What adjacent-pseudo-collapse does is, if the 2nd doc has to be collapsed it
will be sent to the pos 2999 of the relevance results array. If the 3th has to
be collpased too will go to the position 2998 and successively like this.
The algorithm is not applyed when a sortspec is set or plus.considerMoreDocs is
set to false. It neighter is applyed when using MoreLikeThisRequestHanlder.
Example with a query of 9 results:
Results sorted by relevance without pseudo-collapse-algorithm:
doc1 - collapse_field_value 3
doc2 - collapse_field_value 3
doc3 - collapse_field_value 4
doc4 - collapse_field_value 7
doc5 - collapse_field_value 6
doc6 - collapse_field_value 6
doc7 - collapse_field_value 5
doc8 - collapse_field_value 1
doc9 - collapse_field_value 2
Results pseudo-collapsed with plus.considerHowMany = 5
doc1 - collapse_field_value 3
doc3 - collapse_field_value 4
doc4 - collapse_field_value 7
doc5 - collapse_field_value 6
doc2 - collapse_field_value 3*
doc6 - collapse_field_value 6
doc7 - collapse_field_value 5
doc8 - collapse_field_value 1
doc9 - collapse_field_value 2
Results pseudo-collapsed with plus.considerHowMany = 9
doc1 - collapse_field_value 3
doc3 - collapse_field_value 4
doc4 - collapse_field_value 7
doc5 - collapse_field_value 6
doc7 - collapse_field_value 5
doc8 - collapse_field_value 1
doc9 - collapse_field_value 2
doc6 - collapse_field_value 6*
doc2 - collapse_field_value 3*
*pseudo-collapsed documents
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