91 lines
2.5 KiB
Plaintext
91 lines
2.5 KiB
Plaintext
[[query-dsl-exists-query]]
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=== Exists Query
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Returns documents that have at least one non-`null` value in the original field:
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[source,js]
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--------------------------------------------------
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{
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"exists" : { "field" : "user" }
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}
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--------------------------------------------------
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For instance, these documents would all match the above query:
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[source,js]
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--------------------------------------------------
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{ "user": "jane" }
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{ "user": "" } <1>
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{ "user": "-" } <2>
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{ "user": ["jane"] }
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{ "user": ["jane", null ] } <3>
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--------------------------------------------------
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<1> An empty string is a non-`null` value.
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<2> Even though the `standard` analyzer would emit zero tokens, the original field is non-`null`.
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<3> At least one non-`null` value is required.
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These documents would *not* match the above query:
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[source,js]
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--------------------------------------------------
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{ "user": null }
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{ "user": [] } <1>
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{ "user": [null] } <2>
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{ "foo": "bar" } <3>
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--------------------------------------------------
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<1> This field has no values.
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<2> At least one non-`null` value is required.
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<3> The `user` field is missing completely.
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[float]
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==== `null_value` mapping
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If the field mapping includes the <<null-value,`null_value`>> setting
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then explicit `null` values are replaced with the specified `null_value`. For
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instance, if the `user` field were mapped as follows:
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[source,js]
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--------------------------------------------------
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"user": {
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"type": "string",
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"null_value": "_null_"
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}
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--------------------------------------------------
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then explicit `null` values would be indexed as the string `_null_`, and the
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following docs would match the `exists` filter:
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[source,js]
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--------------------------------------------------
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{ "user": null }
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{ "user": [null] }
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--------------------------------------------------
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However, these docs--without explicit `null` values--would still have
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no values in the `user` field and thus would not match the `exists` filter:
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[source,js]
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--------------------------------------------------
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{ "user": [] }
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{ "foo": "bar" }
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--------------------------------------------------
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==== `missing` query
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'missing' query has been removed because it can be advantageously replaced by an `exists` query inside a must_not
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clause as follows:
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[source,js]
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--------------------------------------------------
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"bool": {
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"must_not": {
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"exists": {
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"field": "user"
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}
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}
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}
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--------------------------------------------------
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This query returns documents that have no value in the user field.
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