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From "ASF subversion and git services (JIRA)" <>
Subject [jira] [Commented] (LUCENE-5207) lucene expressions module
Date Wed, 08 Jan 2014 12:02:01 GMT


ASF subversion and git services commented on LUCENE-5207:

Commit 1556508 from [~mikemccand] in branch 'dev/branches/lucene5376'
[ ]

LUCENE-5207, LUCENE-5376: add expressions support to lucene server, so you can define a virtual
field from any JS expression and then sort by that field or retrieve its values for all hits

> lucene expressions module
> -------------------------
>                 Key: LUCENE-5207
>                 URL:
>             Project: Lucene - Core
>          Issue Type: New Feature
>            Reporter: Ryan Ernst
>             Fix For: 4.6, 5.0
>         Attachments: LUCENE-5207.patch, LUCENE-5207.patch, 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 (
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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