ElasticSearch: aggregation on _score field w/ Groovy disabled

Question

Every example I\'ve seen (e.g., ElasticSearch: aggregation on _score field?) for doing aggregations on or related to the _score field seems to require the usage of scripting

Answer 1

One possible approach is to use the other scripting options available. mvel seems not to be possible to be used unless dynamic scripting is enabled. And, unless a more fine-grained control of scripting enable/disable reaches 1.6 version, I don't think is possible to enable dynamic scripting for mvel and not for groovy.

We are left with native and mustache (used for templates) that are enabled by default. I don't think custom scripting can be done with mustache, if it's possible I didn't find a way and we are left with native (Java) scripting.

Here's my take to this:

• create an implementation of NativeScriptFactory:

package com.foo.script;

import java.util.Map;

import org.elasticsearch.script.ExecutableScript;
import org.elasticsearch.script.NativeScriptFactory;

public class MyScriptNativeScriptFactory implements NativeScriptFactory {

    @Override
    public ExecutableScript newScript(Map arg0) {
        return new MyScript();
    }

}

• an implementation of AbstractFloatSearchScript for example:

package com.foo.script;

import java.io.IOException;

import org.elasticsearch.script.AbstractFloatSearchScript;

public class MyScript extends AbstractFloatSearchScript {

    @Override
    public float runAsFloat() {
        try {
            return score();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return 0;
    }

}

• alternatively, build a simple Maven project to tie all together. pom.xml:

    1.5.2
    1.8
    1.8



    
        org.elasticsearch
        elasticsearch
        ${elasticsearch.version}
        compile
    



    src
    
        
            maven-compiler-plugin
            3.1
            
                1.8
                1.8
            
        
    

• build it and get the resulting jar file.
• place the jar inside [ES_folder]/lib

• edit elasticsearch.yml and add script.native.my_script.type: com.foo.script.MyScriptNativeScriptFactory

• restart ES nodes.

• use it in aggregations:

{
  "aggs": {
    "max_score": {
      "max": {
        "script": "my_script",
        "lang": "native"
      }
    }
  }
}

My sample above just returns the _score as a script but, of course, it can be used in more advanced scenarios.

EDIT: if you are not allowed to touch the instances, then I don't think you have any options.