ElasticSearch regex query doesn't work

Question

I am using ES 2.4.6 with Java 8, and i created a document object as following:

@Document(indexName = "airports", type = "airport")
public class Airport {

  @Id
  private String id;

  @Field(type = String)
  private String name;
}

And i successfully search several airport objects to ES, with following names: "San Francisco", "San Mateo", "Santiago", "Palo Alto", "Big San" The JSON content inside ES looks like following:

{
  "took": 2,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "failed": 0
  },
  "hits": {
    "total": 5,
    "max_score": 1,
    "hits": [
      {
        "_index": "airports",
        "_type": "airport",
        "_id": "SSMlsTWIYefbXHCnYEwEY",
        "_score": 1,
        "_source": {
          "id": "SSMlsTWIYefbXHCnYEwEY",
          "name": "Santiago"
        }
      },
      {
        "_index": "airports",
        "_type": "airport",
        "_id": "LlDcKuywPjURNeIISjXLjC",
        "_score": 1,
        "_source": {
          "id": "LlDcKuywPjURNeIISjXLjC",
          "name": "San Mateo"
        }
      },
      {
        "_index": "airports",
        "_type": "airport",
        "_id": "CVIjEHYphSmZIjYbHCMwtkqfKWtEHVh",
        "_score": 1,
        "_source": {
          "id": "CVIjEHYphSmZIjYbHCMwtkqfKWtEHVh",
          "name": "San Francisco"
        }
      },
      {
        "_index": "airports",
        "_type": "airport",
        "_id": "gbntKR",
        "_score": 1,
        "_source": {
          "id": "gbntKR",
          "name": "Palo Alto"
        }
      },
      {
        "_index": "airports",
        "_type": "airport",
        "_id": "bKosUdHeseMMboyaejv",
        "_score": 1,
        "_source": {
          "id": "bKosUdHeseMMboyaejv",
          "name": "Big San"
        }
      }
    ]
  }
}

Then i have following curl command to use regex query to find all airport names staring with "san" ignoring case, i did:

curl -XGET 'localhost:9200/airports/airport/_search?pretty' -H 'Content-Type: application/json' -d'
{
    "query": {
        "regexp":{
            "name": "^(?i)san"
        }
    }
}
'

I use the regex "^(?i)san" directly match against those airport names, it works as expect:

String regex = "^(?i)san";
assertTrue("San Francisco".matches(regex));
assertTrue("San Mateo".matches(regex));
assertTrue("Santiago".matches(regex));
assertTrue(!"Big San".matches(regex));

So does anyone know why ES regex query returns empty result back? Now, if i use "san" as regex, all 4 names return back, and if i use "San", nothing returns back.

Answer 1

You can use Match Phrase Prefix for the problem mentioned above.

 {
  "query": {
    "match_phrase_prefix": {
       "name": "San"
      }
    }
 }

See if it resolves your problem.