ElasticSearch Order By String Length

Question

I am using ElasticSearch via NEST c#. I have large list of information about people

{
   firstName: 'Frank',
   lastName: 'Jones',
   City: 'New York'
}

I'd like to be able to filter and sort this list of items by lastName as well as order by the length so people who only have 5 characters in their name will be at the beginning of the result set then people with 10 characters.

So with some pseudo code I'd like to do something like list.wildcard("j*").sort(m => lastName.length)

Answer 1

You can do the sorting with script-based sorting.

As a toy example, I set up a trivial index with a few documents:

PUT /test_index

POST /test_index/doc/_bulk
{"index":{"_id":1}}
{"name":"Bob"}
{"index":{"_id":2}}
{"name":"Jeff"}
{"index":{"_id":3}}
{"name":"Darlene"}
{"index":{"_id":4}}
{"name":"Jose"}

Then I can order search results like this:

POST /test_index/_search
{
   "query": {
      "match_all": {}
   },
   "sort": {
      "_script": {
         "script": "doc['name'].value.length()",
         "type": "number",
         "order": "asc"
      }
   }
}
...
{
   "took": 2,
   "timed_out": false,
   "_shards": {
      "total": 5,
      "successful": 5,
      "failed": 0
   },
   "hits": {
      "total": 4,
      "max_score": null,
      "hits": [
         {
            "_index": "test_index",
            "_type": "doc",
            "_id": "1",
            "_score": null,
            "_source": {
               "name": "Bob"
            },
            "sort": [
               3
            ]
         },
         {
            "_index": "test_index",
            "_type": "doc",
            "_id": "4",
            "_score": null,
            "_source": {
               "name": "Jose"
            },
            "sort": [
               4
            ]
         },
         {
            "_index": "test_index",
            "_type": "doc",
            "_id": "2",
            "_score": null,
            "_source": {
               "name": "Jeff"
            },
            "sort": [
               4
            ]
         },
         {
            "_index": "test_index",
            "_type": "doc",
            "_id": "3",
            "_score": null,
            "_source": {
               "name": "Darlene"
            },
            "sort": [
               7
            ]
         }
      ]
   }
}

To filter by length, I can use a script filter in a similar way:

POST /test_index/_search
{
   "query": {
      "filtered": {
         "query": {
            "match_all": {}
         },
         "filter": {
            "script": {
               "script": "doc['name'].value.length() > 3",
               "params": {}
            }
         }
      }
   },
   "sort": {
      "_script": {
         "script": "doc['name'].value.length()",
         "type": "number",
         "order": "asc"
      }
   }
}
...
{
   "took": 3,
   "timed_out": false,
   "_shards": {
      "total": 5,
      "successful": 5,
      "failed": 0
   },
   "hits": {
      "total": 3,
      "max_score": null,
      "hits": [
         {
            "_index": "test_index",
            "_type": "doc",
            "_id": "4",
            "_score": null,
            "_source": {
               "name": "Jose"
            },
            "sort": [
               4
            ]
         },
         {
            "_index": "test_index",
            "_type": "doc",
            "_id": "2",
            "_score": null,
            "_source": {
               "name": "Jeff"
            },
            "sort": [
               4
            ]
         },
         {
            "_index": "test_index",
            "_type": "doc",
            "_id": "3",
            "_score": null,
            "_source": {
               "name": "Darlene"
            },
            "sort": [
               7
            ]
         }
      ]
   }
}

Here's the code I used:

http://sense.qbox.io/gist/22fef6dc5453eaaae3be5fb7609663cc77c43dab

P.S.: If any of the last names will contain spaces, you might want to use "index": "not_analyzed" on that field.