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10ee0f2878
* Clarify that field data cache includes global ordinals * Describe that the cache should be cleared once the limit is reached * Clarify that the `_id` field does not supported aggregations anymore * Fold the `fielddata` mapping parameter page into the `text field docs * Improve cross-linking
46 lines
1.3 KiB
Text
46 lines
1.3 KiB
Text
[[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>>. The `_id` can either be assigned at
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indexing time, or a unique `_id` can be generated by {es}. This field is not
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configurable in the mappings.
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The value of the `_id` field is accessible in queries such as `term`,
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`terms`, `match`, and `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-000001/_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-000001/_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-000001/_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 `_id` field is restricted from use in aggregations, sorting, and scripting.
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In 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 into another field that has
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`doc_values` 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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