47 lines
1.2 KiB
Plaintext
47 lines
1.2 KiB
Plaintext
[[mapping-id-field]]
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=== `_id` field
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Each document has an `_id` that uniquely identifies it, which is indexed
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so that documents can be looked up either with the <<docs-get,GET API>> or the
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<<query-dsl-ids-query,`ids` query>>.
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The value of the `_id` field is accessible in certain queries (`term`,
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`terms`, `match`, `query_string`, `simple_query_string`).
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[source,console]
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--------------------------
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# Example documents
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PUT my_index/_doc/1
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{
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"text": "Document with ID 1"
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}
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PUT my_index/_doc/2&refresh=true
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{
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"text": "Document with ID 2"
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}
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GET my_index/_search
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{
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"query": {
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"terms": {
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"_id": [ "1", "2" ] <1>
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}
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}
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}
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--------------------------
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<1> Querying on the `_id` field (also see the <<query-dsl-ids-query,`ids` query>>)
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The value of the `_id` field is also accessible in aggregations or for sorting,
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but doing so is discouraged as it requires to load a lot of data in memory. In
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case sorting or aggregating on the `_id` field is required, it is advised to
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duplicate the content of the `_id` field in another field that has `doc_values`
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enabled.
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[NOTE]
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==================================================
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`_id` is limited to 512 bytes in size and larger values will be rejected.
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==================================================
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