60 lines
1.3 KiB
Plaintext
60 lines
1.3 KiB
Plaintext
[[mapping-field-names-field]]
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=== `_field_names` field
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The `_field_names` field indexes the names of every field in a document that
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contains any value other than `null`. This field is used by the
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<<query-dsl-exists-query,`exists`>> query to find documents that
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either have or don't have any non-+null+ value for a particular field.
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The value of the `_field_names` field is accessible in queries:
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[source,js]
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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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"title": "This is a document"
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}
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PUT my_index/_doc/2?refresh=true
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{
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"title": "This is another document",
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"body": "This document has a body"
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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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"_field_names": [ "title" ] <1>
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}
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}
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}
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--------------------------
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// CONSOLE
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<1> Querying on the `_field_names` field (also see the <<query-dsl-exists-query,`exists`>> query)
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==== Disabling `_field_names`
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Because `_field_names` introduce some index-time overhead, you might want to
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disable this field if you want to optimize for indexing speed and do not need
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`exists` queries.
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[source,js]
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--------------------------------------------------
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PUT tweets
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{
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"mappings": {
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"_doc": {
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"_field_names": {
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"enabled": false
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}
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}
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}
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}
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--------------------------------------------------
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// CONSOLE
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