原英文版地址: https://www.elastic.co/guide/en/elasticsearch/reference/7.7/mapping-id-field.html, 原文档版权归 www.elastic.co 所有
本地英文版地址: ../en/mapping-id-field.html
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Elasticsearch Guide [7.7] » Mapping » Meta-Fields » _id field
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_id fieldedit

Each document has an _id that uniquely identifies it, which is indexed so that documents can be looked up either with the GET API or the ids query.

The value of the _id field is accessible in certain queries (term, terms, match, query_string, simple_query_string).

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

PUT my_index/_doc/2?refresh=true
{
  "text": "Document with ID 2"
}

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

Querying on the _id field (also see the ids query)

The value of the _id field is also accessible in aggregations or for sorting, but doing so is discouraged as it requires to load a lot of data in memory. In case sorting or aggregating on the _id field is required, it is advised to duplicate the content of the _id field in another field that has doc_values enabled.

_id is limited to 512 bytes in size and larger values will be rejected.

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