Each document indexed is associated with a _type (see the section called “Mapping Typesedit”) and an _id. The _id field is not indexed as its value can be derived automatically from the _uid field.

The value of the _id field is accessible in certain queries (term, terms, match, query_string, simple_query_string), but not in aggregations, scripts or when sorting, where the _uid field should be used instead:

# Example documents
PUT my_index/my_type/1
{
  "text": "Document with ID 1"
}

PUT my_index/my_type/2&refresh=true
{
  "text": "Document with ID 2"
}

GET my_index/_search
{
  "query": {
    "terms": {
      "_id": [ "1", "2" ] 
    }
  }
}