# Trying to write a Facet to replace a Lucene collector

**URL:** <https://discuss.elastic.co/t/trying-to-write-a-facet-to-replace-a-lucene-collector/8602>\
**Category:** Elasticsearch\
**Created:** [August 1, 2012, 9:57pm UTC](https://discuss.elastic.co/t/trying-to-write-a-facet-to-replace-a-lucene-collector/8602 "2012-08-01T21:57:09Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![phill](https://avatars.discourse-cdn.com/v4/letter/p/779978/32.png) [@phill](https://discuss.elastic.co/u/phill)\
**Post date:** [August 1, 2012, 9:57pm UTC](https://discuss.elastic.co/t/trying-to-write-a-facet-to-replace-a-lucene-collector/8602/1 "2012-08-01T21:57:09Z")

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I'm thinking I can replace a Lucene collector I have with a Facet with a  
script.  
I'm starting to experiment using a term stats facet or statistics facet  
to get the map-reduce behavior (mostly the map behavior) I'm looking  
for. If I really needed to reduce my results from all shards, I'd have  
to go down the custom Facet approach, but for now it looks doable as a  
variation on a statistical collector with possible a bit of post  
processing after I get the results.

Just to establish a concrete example, if I have documents that represent  
files, including a path, mod\_date, and file\_size. I might run a script  
to transform the path to something less (e.g. some appropriate  
ancestor/parent directory) and gather statistics about dates of all  
documents in that directory or the whole directory tree below a  
directory using a term stats facet and script transforming where the  
transformed path|as the key\_field and the mod date as the value\_field.

This could be used in an application where there is an interface that  
shows info about the folders containing the documents found as well as  
the document search results.

|My first attempt I'll be writing a native script, so my 1st question is:

Question 1: Can I add a script definition dynamically via the REST API?

$ curl -XPUT '[http://172.16.0.164:9200/test\_index/\_settings](http://172.16.0.164:9200/test_index/_settings)' -d '  
script.native.myScript.type: com.me.scripts.MyNativeScriptFactory  
'  
based on:  
|http://www.elasticsearch.org/guide/reference/modules/scripting.html||  
The above should register a script named "myScript".

||But this api is on the page about modules, so I'm not sure if this  
setting is actually part of a module and thus will be in the right place  
when it is needed.

I will eventually declare such a script at the cluster level, but the  
question remains about using the REST API.

Question 1a: What is a quick way to show that the above setting worked,  
but the class is not (yet) found?

Question 2: Can I return either false or a new value from the same script?

I see that scripts for term facet can be written to return either a  
boolean or a new key.  
I'm assuming I can filter out unwanted or redundant values by returning  
a boolean false when the term value is irrelevant, but alternately a new  
transformed key when I want to use send on a transformed value.

Question 3: ||Is a native script created (the factory called) once per  
facet invocation or once per document hit? |

|If I did try to filter out "redundant" keys (see previous question),  
I'd have to have a way to know that my script is starting on a new query  
or facet and not just being asked to process an isolated document.

thanks in advance.

-Paul  
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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [July 6, 2017, 3:18am UTC](https://discuss.elastic.co/t/trying-to-write-a-facet-to-replace-a-lucene-collector/8602/2 "2017-07-06T03:18:04Z")

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