71 lines
2.1 KiB
Plaintext
71 lines
2.1 KiB
Plaintext
[[query-dsl-has-parent-query]]
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=== Has Parent Query
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The `has_parent` query works the same as the
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<<query-dsl-has-parent-filter,has_parent>>
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filter, by automatically wrapping the filter with a constant_score (when
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using the default score type). It has the same syntax as the
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<<query-dsl-has-parent-filter,has_parent>>
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filter.
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[source,js]
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--------------------------------------------------
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{
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"has_parent" : {
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"parent_type" : "blog",
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"query" : {
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"term" : {
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"tag" : "something"
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}
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}
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}
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}
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--------------------------------------------------
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[float]
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==== Scoring capabilities
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The `has_parent` also has scoring support. The
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supported score types are `score` or `none`. The default is `none` and
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this ignores the score from the parent document. The score is in this
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case equal to the boost on the `has_parent` query (Defaults to 1). If
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the score type is set to `score`, then the score of the matching parent
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document is aggregated into the child documents belonging to the
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matching parent document. The score type can be specified with the
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`score_mode` field inside the `has_parent` query:
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[source,js]
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--------------------------------------------------
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{
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"has_parent" : {
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"parent_type" : "blog",
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"score_mode" : "score",
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"query" : {
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"term" : {
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"tag" : "something"
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}
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}
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}
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}
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--------------------------------------------------
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[float]
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==== Memory Considerations
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In order to support parent-child joins, all of the (string) parent IDs
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must be resident in memory (in the <<index-modules-fielddata,field data cache>>.
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Additionaly, every child document is mapped to its parent using a long
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value (approximately). It is advisable to keep the string parent ID short
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in order to reduce memory usage.
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You can check how much memory is being used by the ID cache using the
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<<indices-stats,indices stats>> or <<cluster-nodes-stats,nodes stats>>
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APIS, eg:
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[source,js]
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--------------------------------------------------
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curl -XGET "http://localhost:9200/_stats/id_cache?pretty&human"
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--------------------------------------------------
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