Elasticsearch exists filter how to make an empty string as null value?

Question

I tried to index a name field to elasticsearch, the name maybe is a string or a empty string(""), I want to search all name which contain the empty value, so I use the exists filter, but for exists filter, the empty value is not a null value.

https://www.elastic.co/guide/en/elasticsearch/reference/1.4/query-dsl-exists-filter.html

query dsl:

{ "filter" : {
                "exists" : { "field" : "name" }
            } 
}

How to make the empty string as a null value for elasticsearch exist filter? Anyone has good idea?

You can combine missing filter. "filter": {"missing" : { "field" : "name" }} — Toni
– Toni, Commented Apr 22, 2016 at 8:54

Community · Accepted Answer · 2017-05-23 12:13:53Z

3

The term filter should do the job:

    {
      "term": {
        "name": ""
      }
    }

Just tried it with some of my data and got results, but might depend if your fields are "not-analyzed" (like mine) or not.

Update: Just found this similar question which has a much more detailed answer: Find documents with empty string value on elasticsearch

edited May 23, 2017 at 12:13

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answered Apr 22, 2016 at 10:43

Sebastian

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1 Comment

pangpang Over a year ago

I hope to use exists filter.

Val · Accepted Answer · 2016-04-22 08:41:29Z

0

You can try searching by using a script filter instead in order to test the length of the string

{
  "query": {
    "script": {
      "script": "doc.name.value?.size() == 0"
    }
  }
}

answered Apr 22, 2016 at 8:41

Val

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2 Comments

Sebastian Over a year ago

Scripts are slow and should be avoided whenever possible.

Val Over a year ago

Sebastian is right, his solution works best... only if you have not_analyzed field, otherwise it won't work.

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