COALESCE in Elasticsearch

Question

I am using MongoId with ruby on rails. For my search I am using elasticsearch.

I have a date field. It is optional field and I use it as a stop date. In my search I would like to know if my stop date is greater than the search stop date. Example

{
  "range": {
    "stop_date": {
      "gt": "#{search_stop}"
    }
  }
}

The issue when the stop date is null I need it to be returned in this query, but it is not as the stop date is null or not in the document.

I need when the stop date is null or not in the document the search to be set as a default value like 21/31/2100.

Any advice will be really appreciated...

Answer 1

There are two approaches to this.

1. One is to use null_value to stop_date in the mapping. This way , when you are indexing , if stop_date field is missing , the value set as null_value will go to the lucene reverse index. But the issue with this approach is that , this value would be static across all documents and acorss all times. Null_value - http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/mapping-core-types.html

2. Second approach would be to change the query

    { "query": { "filtered": { "filter": { "or": [ { "range": { "stop_date": { "gt": "#{search_stop}" } } }, { "missing": { "field": "stop_date" } } ] } } } } 

   Here a document is matched if the stop_date field is missing or when the date range filter matched.

My recommendation would be to use second one.