70 lines
2.2 KiB
Plaintext
70 lines
2.2 KiB
Plaintext
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[[mapping-routing-field]]
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=== `_routing`
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The routing field allows to control the `_routing` aspect when indexing
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data and explicit routing control is required.
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[float]
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==== store / index
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The first thing the `_routing` mapping does is to store the routing
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value provided (`store` set to `yes`) and index it (`index` set to
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`not_analyzed`). The reason why the routing is stored by default is so
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reindexing data will be possible if the routing value is completely
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external and not part of the docs.
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[float]
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==== required
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Another aspect of the `_routing` mapping is the ability to define it as
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required by setting `required` to `true`. This is very important to set
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when using routing features, as it allows different APIs to make use of
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it. For example, an index operation will be rejected if no routing value
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has been provided (or derived from the doc). A delete operation will be
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broadcasted to all shards if no routing value is provided and `_routing`
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is required.
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[float]
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==== path
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The routing value can be provided as an external value when indexing
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(and still stored as part of the document, in much the same way
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`_source` is stored). But, it can also be automatically extracted from
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the index doc based on a `path`. For example, having the following
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mapping:
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[source,js]
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--------------------------------------------------
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{
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"comment" : {
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"_routing" : {
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"required" : true,
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"path" : "blog.post_id"
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}
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}
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}
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--------------------------------------------------
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Will cause the following doc to be routed based on the `111222` value:
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[source,js]
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--------------------------------------------------
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{
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"text" : "the comment text"
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"blog" : {
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"post_id" : "111222"
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}
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}
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--------------------------------------------------
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Note, using `path` without explicit routing value provided required an
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additional (though quite fast) parsing phase.
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[float]
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==== id uniqueness
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When indexing documents specifying a custom `_routing`, the uniqueness
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of the `_id` is not guaranteed throughout all the shards that the index
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is composed of. In fact, documents with the same `_id` might end up in
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different shards if indexed with different `_routing` values.
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