Elasticsearch - how to check for key exist script query parameters?

Question

Is there any way to return null if there is no corresponding value?

example) Since params do not have a field4 value, I want the null value to be returned to the syn variable.

"aggs": {
    "countries": {
      "terms": {
        "script": {
          "params": {
            "field1": "country",
            "field2": "test",
            "field3": "test"
          },
          "inline": "def syn = field4; if (syn == null) doc[country].value;"
        }
      }
    }
  }

Currently, errors always occur if there is no corresponding value.

"caused_by": {
   "type": "missing_property_exception",
   "reason": "No such property: field1 for class: e5ce2464b456f9c0fa360269abc927e65998ecf7"
}

I am using groovy and elasticsearch version 2.2

I can't use Python or JavaScript, which requires additional plug-ins to be installed.

How can I get a null value without causing an error if there is no value?

Thanks

Val · Accepted Answer · 2021-12-01 04:31:14Z

2

You have a boolean value called empty that indicates you whether the document has such a field or not.

So you should do it this way

      "inline": "def syn = field4 ?: 'dummy'; return (doc[syn].empty) ? null : doc[syn].value;"

UPDATE: To detect a missing parameter variable in Groovy is trivial if we know the script class name. But since the script class is created dynamically (e.g. e5ce2464b456f9c0fa360269abc927e65998ecf7), it makes the process not trivial at all. One way to circumvent this is to add a try/catch block around your code, so that the code can fail but at least we can catch it, basically like this:

      "inline": "try { def syn = field4; return (doc[syn].empty) ? null : doc[syn].value; } catch (e) { return null } "

However, ES introduced some security hardening and class whitelisting for scripting in 2.2. One way to achieve this is to whitelist a few Exception classes in your .java.policy file, like this:

grant {
  permission org.elasticsearch.script.ClassPermission "java.lang.Throwable";
  permission org.elasticsearch.script.ClassPermission "java.lang.Exception";
  permission org.elasticsearch.script.ClassPermission "groovy.lang.GroovyException";
};

edited Dec 1, 2021 at 4:31

answered Nov 30, 2021 at 6:52

Val

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7 Comments

nkhcode Over a year ago

Same Error Occured def syn = field4; There seems to be an error in that part before checking the importy.

Val Over a year ago

Oh I see what you mean now. Let me update my answer

Val Over a year ago

I've updated my answer, can you try again? Sorry I cannot test it, because I can't install 2.2 anymore, too old.

nkhcode Over a year ago

not work same error occured

Val Over a year ago

Ok, I did some more research and updated my answer. Please give it a try

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