# Accessing number of matching document inside a script

**URL:** <https://discuss.elastic.co/t/accessing-number-of-matching-document-inside-a-script/129238>\
**Category:** Elasticsearch\
**Created:** [April 24, 2018, 7:17am UTC](https://discuss.elastic.co/t/accessing-number-of-matching-document-inside-a-script/129238 "2018-04-24T07:17:50Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![vincent.arnaud90](https://avatars.discourse-cdn.com/v4/letter/v/c89c15/32.png) [@vincent.arnaud90](https://discuss.elastic.co/u/vincent.arnaud90)\
**Post date:** [April 24, 2018, 7:17am UTC](https://discuss.elastic.co/t/accessing-number-of-matching-document-inside-a-script/129238/1 "2018-04-24T07:17:50Z")

</div>

Hi,  
I developped a custom plugin to modify the scores, according to some internal criteria, of documents matching a user query.  
My problem is : the function that modifies the score is very expensive and I do not want to run it when the user query matches a very large number of documents.  
I am wondering how to directly get this number of matching documents without putting a counter.

```
private static class MyExpertScriptEngine implements ScriptEngine {
   
    //choosen arbitrarily
    public static final double THRESHOLD = 10000;
   
    @Override
    public <T> T compile(String scriptName, String scriptSource, ScriptContext<T> context, Map<String, String> params) {
        // we use the script "source" as the script identifier
        if ("pure_df".equals(scriptSource)) {
            SearchScript.Factory factory = (p, lookup) -> new SearchScript.LeafFactory() {
		if (numberOfMatchingDocuments > THRESHOLD ){
                    throw InternalException("Cannot apply the expensive cost function because the number of matching documents is greater than " + THRESHOLD );	
                }     

                @Override
                public SearchScript newInstance(LeafReaderContext context) throws IOException {
                    return new SearchScript(p, lookup, context) {
                        
                        @Override
                        public double runAsDouble() {
                           // run our expensive function to modify the score of matching documents. 
                            
                    	};              
            };
            return context.factoryClazz.cast(factory);
        }
    }
}

POST /_search
{
  "query": {
    "function_score": {
      "query": {
        user_query
      },
      "functions": [
        {
          "script_score": {
            "script": {
                "source": "pure_df",
                "lang" : "expert_scripts",
                "params": {
                    "param1": "value1",
                    "params2": "value2"
                }
            }
          }
        }
      ]
    }
  }
}

```

Thanks for your help

---

<div class="post-metadata">

**Author:** ![Mark\_Harwood](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/mark_harwood/32/10538_2.png) [@Mark\_Harwood](https://discuss.elastic.co/u/Mark_Harwood)\
**Post date:** [April 27, 2018, 9:39am UTC](https://discuss.elastic.co/t/accessing-number-of-matching-document-inside-a-script/129238/2 "2018-04-27T09:39:58Z")

</div>

If your "expensive" function is packaged as a query you could looking at using [rescoring](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-request-rescore.html) to limit the number of docs you apply this logic to

---

<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:** [May 25, 2018, 9:40am UTC](https://discuss.elastic.co/t/accessing-number-of-matching-document-inside-a-script/129238/3 "2018-05-25T09:40:00Z")

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