accessing _id or _parent fields in script query in elasticsearch

Question

when writing a search query with a script, I can access fields using "doc['myfield']"

curl -XPOST 'http://localhost:9200/index1/type1/_search' -d '
{
  "query": {
    "filtered": {
      "query": {
        "match_all": {}
      },
      "filter": {
        "script": {
          "script": "doc[\"myfield\"].value>0",
          "params": {},
          "lang":"python"
        }
      }
    }
  }
}'

how do I go about accessing the _id or _parent fields?

The "ctx" object does not seem to be available in a search query (while it is accessible in an update API request, why?).

Mind you, I am using the python language instead of mvel, but both of them pose the same question.

Answer 1

By default, both document id and parent id are indexed in uid format: type#id. Elasticsearch provides a few methods that can be used to extract type and id from uid string. Here is an example of using these methods in MVEL:

curl -XDELETE localhost:9200/test
curl -XPUT localhost:9200/test -d '{
    "settings": {
        "index.number_of_shards": 1,
        "index.number_of_replicas": 0
    },
    "mappings": {
        "doc": {
            "properties": {
                "name": {
                    "type": "string"
                }
            }
        },
        "child_doc": {
            "_parent": {
                "type": "doc"
            },
            "properties": {
                "name": {
                    "type": "string"
                }
            }
        }
    }
}'
curl -XPUT "localhost:9200/test/doc/1" -d '{"name": "doc 1"}'
curl -XPUT "localhost:9200/test/child_doc/1-1?parent=1" -d '{"name": "child 1-1 of doc 1"}'
curl -XPOST "localhost:9200/test/_refresh"
echo
curl "localhost:9200/test/child_doc/_search?pretty=true" -d '{
    "script_fields": {
        "uid_in_script": {
            "script": "doc[\"_uid\"].value"
        },
        "id_in_script": {
            "script": "org.elasticsearch.index.mapper.Uid.idFromUid(doc[\"_uid\"].value)"
        },
        "parent_uid_in_script": {
            "script": "doc[\"_parent\"].value"
        },
        "parent_id_in_script": {
            "script": "org.elasticsearch.index.mapper.Uid.idFromUid(doc[\"_parent\"].value)"
        },
        "parent_type_in_script": {
            "script": "org.elasticsearch.index.mapper.Uid.typeFromUid(doc[\"_parent\"].value)"
        }
    }
}'
echo