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* [DOCS] Rewords _field_names documentation Corrects the language around when we write to `_field_names` and when you might want to disable it given that n recent versions it does not carry the indexing overhead it once did. Relates to #30862 * Update wording following review
36 lines
1.2 KiB
Plaintext
36 lines
1.2 KiB
Plaintext
[[mapping-field-names-field]]
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=== `_field_names` field
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The `_field_names` field used to index the names of every field in a document that
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contains any value other than `null`. This field was 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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Now the `_field_names` field only indexes the names of fields that have
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`doc_values` and `norms` disabled. For fields which have either `doc_values`
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or `norm` enabled the <<query-dsl-exists-query,`exists`>> query will still
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be available but will not use the `_field_names` field.
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==== Disabling `_field_names`
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Disabling `_field_names` is often not necessary because it no longer
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carries the index overhead it once did. If you have a lot of fields
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which have `doc_values` and `norms` disabled and you do not need to
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execute `exists` queries using those fields you might want to disable
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`_field_names` be adding the following to the mappings:
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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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