Add field validation for range aggregation field option

[ppf2]

Elasticsearch version: 1.7, 2.3

Consider the following example, if field is set to a field that does not exist, no errors are thrown and instead only the range aggregation is returned and the max value is not returned.

PUT rangeagg
{
  "mappings": {
    "type":{
      "properties": {
        "intField1":{
          "type": "integer"
        },
        "intField2":{
          "type": "integer"
        }
      }
    }
  }
}

POST rangeagg/type/1
{
  "intField1": 4,
  "intField2": 3
}

GET /rangeagg/_search
{
  "aggs": {
    "test": {
      "range": {
        "field": "whatever", 
        "script" : "doc['intField1'].value - doc['intField2'].value",
        "ranges": [
          {
            "from": 0,
            "to": 2
          }
        ]
      },
      "aggs": {
        "max": {
          "max": {
            "field": "intField1"
          }
        }
      }
    }
  }
} 

Returns:

"aggregations": {
      "test": {
         "buckets": [
            {
               "key": "0.0-2.0",
               "from": 0,
               "from_as_string": "0.0",
               "to": 2,
               "to_as_string": "2.0",
               "doc_count": 0
            }
         ]
      }
   }

[jpountz]

The problem is that if we fail search requests on missing fields, then cross-index search requests will report failed shards as soon as any of the indices does not contain all fields that are used in aggregations. I am pretty sure many users rely on this behaviour.

And I'd like to avoid adding a setting.

[colings86]

Discussed in FixItFriday. We agreed with @jpountz that we don't want to fail on missing fields because of the cross-index search request use case which is heavily used. Adding a specific setting for this is also not desirable but we thought in the case where you are wanting to specify a script to work on each value of a field rathe ran once on each document we should specify the script using value_script instead of script.

This would allow us to add validation to error if you specify script and field since this would then be invalid.

To give an upgrade path for this change we should do the following:

In 5.x:

• Add the value_script parameter to specify a script to execute on each value
• Specifying script and field will still work for BWC but will log to the deprecation logger
• Deprecate the use of script and field together in the documentation in favour of using value_script and field

In 6.0:

• Throw a error during parsing if script is used with value_script

/cc @clintongormley