Retrieving information from elasticsearch, by the order of the input array

Here is one way you can do it, with custom scripted scoring.

First I created some dummy data:

curl -XPUT "http://localhost:9200/test_index"

curl -XPOST "http://localhost:9200/test_index/_bulk " -d'
{ "index" : { "_index" : "test_index", "_type" : "docs", "_id" : 1 } }
{ "name" : "Document 1", "id" : 1 }
{ "index" : { "_index" : "test_index", "_type" : "docs", "_id" : 2 } }
{ "name" : "Document 2", "id" : 2 }
{ "index" : { "_index" : "test_index", "_type" : "docs", "_id" : 3 } }
{ "name" : "Document 3", "id" : 3 }
{ "index" : { "_index" : "test_index", "_type" : "docs", "_id" : 4 } }
{ "name" : "Document 4", "id" : 4 }
{ "index" : { "_index" : "test_index", "_type" : "docs", "_id" : 5 } }
{ "name" : "Document 5", "id" : 5 }
{ "index" : { "_index" : "test_index", "_type" : "docs", "_id" : 6 } }
{ "name" : "Document 6", "id" : 6 }
{ "index" : { "_index" : "test_index", "_type" : "docs", "_id" : 7 } }
{ "name" : "Document 7", "id" : 7 }
{ "index" : { "_index" : "test_index", "_type" : "docs", "_id" : 8 } }
{ "name" : "Document 8", "id" : 8 }
{ "index" : { "_index" : "test_index", "_type" : "docs", "_id" : 9 } }
{ "name" : "Document 9", "id" : 9 }
{ "index" : { "_index" : "test_index", "_type" : "docs", "_id" : 10 } }
{ "name" : "Document 10", "id" : 10 }
'

I used an "id" field even though it's redundant, since the "_id" field gets converted to a string, and the scripting is easier with integers.

You can get back a specific set of docs by id with the ids filter:

curl -XPOST "http://localhost:9200/test_index/_search" -d'
{
   "filter": {
      "ids": {
         "type": "docs",
         "values": [ 1, 8, 2, 5 ]
      }
   }
}'

but these will not necessarily be in the order you want them. Using script based scoring, you can define your own ordering based on document ids.

Here I pass in a parameter that is a list of objects that relate ids to score. The scoring script simply loops through them until it finds the current document id and returns the predetermined score for that document (or 0 if it isn't listed).

curl -XPOST "http://localhost:9200/test_index/_search" -d'
{
   "filter": {
      "ids": {
         "type": "docs",
         "values": [ 1, 8, 2, 5 ]
      }
   },
   "sort" : {
        "_script" : {
            "script" : "for(i:scoring) { if(doc[\"id\"].value == i.id) return i.score; } return 0;",
            "type" : "number",
            "params" : {
                "scoring" : [
                    { "id": 1, "score": 1 },
                    { "id": 8, "score": 2 },
                    { "id": 2, "score": 3 },
                    { "id": 5, "score": 4 }
                ]
            },
            "order" : "asc"
        }
    }
}'

and the documents are returned in the proper order:

{
   "took": 11,
   "timed_out": false,
   "_shards": {
      "total": 2,
      "successful": 2,
      "failed": 0
   },
   "hits": {
      "total": 4,
      "max_score": null,
      "hits": [
         {
            "_index": "test_index",
            "_type": "docs",
            "_id": "1",
            "_score": null,
            "_source": {
               "name": "Document 1",
               "id": 1
            },
            "sort": [
               1
            ]
         },
         {
            "_index": "test_index",
            "_type": "docs",
            "_id": "8",
            "_score": null,
            "_source": {
               "name": "Document 8",
               "id": 8
            },
            "sort": [
               2
            ]
         },
         {
            "_index": "test_index",
            "_type": "docs",
            "_id": "2",
            "_score": null,
            "_source": {
               "name": "Document 2",
               "id": 2
            },
            "sort": [
               3
            ]
         },
         {
            "_index": "test_index",
            "_type": "docs",
            "_id": "5",
            "_score": null,
            "_source": {
               "name": "Document 5",
               "id": 5
            },
            "sort": [
               4
            ]
         }
      ]
   }
}

Here is a runnable example: http://sense.qbox.io/gist/01b28e5c038c785f0844abb7c01a71d69a32a2f4