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https://issues.apache.org/jira/browse/LUCENE-5207?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13766021#comment-13766021
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Michael McCandless commented on LUCENE-5207:
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Wow, this sounds awesome!
So, you can use an arbitrary JavaScript expression to combine DV fields and
score into a new dynamic field for sorting?
E.g., a blended relevance + recency sort (which I do w/ a custom comparator now
on http://jirasearch.mikemccandless.com).
> lucene expressions module
> -------------------------
>
> Key: LUCENE-5207
> URL: https://issues.apache.org/jira/browse/LUCENE-5207
> Project: Lucene - Core
> Issue Type: New Feature
> Reporter: Ryan Ernst
> Attachments: LUCENE-5207.patch
>
>
> Expressions are geared at defining an alternative ranking function (e.g.
> incorporating the text relevance score and other field values/ranking
> signals). So they are conceptually much more like ElasticSearch's scripting
> support (http://www.elasticsearch.org/guide/reference/modules/scripting/)
> than solr's function queries.
> Some additional notes:
> * In addition to referring to other fields, they can also refer to other
> expressions, so they can be used as "computed fields".
> * You can rank documents easily by multiple expressions (its a SortField at
> the end), e.g. Sort by year descending, then some function of score price and
> time ascending.
> * The provided javascript expression syntax is much more efficient than using
> a scripting engine, because it does not have dynamic typing (compiles to
> .class files that work on doubles). Performance is similar to writing a
> custom FieldComparator yourself, but much easier to do.
> * We have solr integration to contribute in the future, but this is just the
> standalone lucene part as a start. Since lucene has no schema, it includes an
> implementation of Bindings (SimpleBindings) that maps variable names to
> SortField's or other expressions.
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