Script field using expression - Only member variable [value] or member method is available

Question

I am trying to use script fields in my request. I included sandbox scripts and tried to use an expression to compute a new field.

The fact is that I get the following error:

{ "type": "expression_script_compilation_exception", "reason": "Only the member variable [value] or member methods may be accessed on a field when not accessing the field directly" } 

It seems that only "value" is available. What am I missing here?

When executing the following query:

 { "query": { "match_all": {} }, "script_fields" : { "field1" : { "script" : { "lang": "expression", "inline": "doc['about.hobbies'].empty" } } } } 

Matching:

 { "my_index": { "mappings": { "type": { "properties": { "about": { "properties": { "hobbies": { "type": "string", "analyzer": "lowercase" } } } } } } } 

A little explanation: I have a field that can contain a list of string values.

 "hobbies": ["a","b",c"] 

and it may also be empty. I want to have a script field of type boolean that will be true if the list is not empty, and false when the list is empty.

Update : reading a few more, I meet this documentation on lucene expression scripts

There are several limitations to other script languages:

• Only numeric fields are available.
• Saved fields not available
• If the field is sparse (only some documents contain a value), documents that do not have a field will have a value of 0

My field is of type String, could that be the problem? If so, is there any other way to use script fields based on string fields? perhaps using groovy?

Answer 1

I think the problem is that the field is a nested object, if I read the documents correctly, then doc ['field'] only supports simple term fields.

Please note, however, that the doc notation [...] allows only simple meaningful fields (cannot return a json object from it) and makes sense only in unanalyzed or one-time fields.

However using _source worked for me

  "script_fields" : { "field1" : { "script" : "_source.about.hobbies.size() > 0" } },