position_increment_gap

Analyzed string fields take term positions into account, in order to be able to support proximity or phrase queries. When indexing string fields with multiple values a "fake" gap is added between the values to prevent most phrase queries from matching across the values. The size of this gap is configured using position_increment_gap and defaults to 100.

For example:

PUT /my_index/groups/1
{
    "names": [ "John Abraham", "Lincoln Smith"]
}

GET /my_index/groups/_search
{
    "query": {
        "match_phrase": {
            "names": "Abraham Lincoln" 
        }
    }
}

GET /my_index/groups/_search
{
    "query": {
        "match_phrase": {
            "names": "Abraham Lincoln",
            "slop": 101 
        }
    }
}

This phrase query doesn’t match our document which is totally expected.

This phrase query matches our document, even though Abraham and Lincoln are in separate strings, because slop > position_increment_gap.

The position_increment_gap can be specified in the mapping. For instance:

PUT my_index
{
  "mappings": {
    "my_type": {
      "properties": {
        "names": {
          "type": "string",
          "position_increment_gap": 0 
        }
      }
    }
  }
}

PUT /my_index/groups/1
{
    "names": [ "John Abraham", "Lincoln Smith"]
}

GET /my_index/groups/_search
{
    "query": {
        "match_phrase": {
            "names": "Abraham Lincoln" 
        }
    }
}

The first term in the next array element will be 0 terms apart from the last term in the previous array element.

The phrase query matches our document which is weird, but its what we asked for in the mapping.

The position_increment_gap setting is allowed to have different settings for fields of the same name in the same index. Its value can be updated on existing fields using the PUT mapping API.