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* Remove `es-test-dir` book-scoped variable * Remove `plugins-examples-dir` book-scoped variable * Remove `:dependencies-dir:` and `:xes-repo-dir:` book-scoped variables - In `index.asciidoc`, two variables (`:dependencies-dir:` and `:xes-repo-dir:`) were removed. - In `sql/index.asciidoc`, the `:sql-tests:` path was updated to fuller path - In `esql/index.asciidoc`, the `:esql-tests:` path was updated idem * Replace `es-repo-dir` with `es-ref-dir` * Move `:include-xpack: true` to few files that use it, remove from index.asciidoc
146 lines
4 KiB
Text
146 lines
4 KiB
Text
[[knn-search-api]]
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=== kNN search API
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++++
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<titleabbrev>kNN search</titleabbrev>
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++++
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deprecated::[8.4.0,"The kNN search API has been replaced by the <<search-api-knn, `knn` option>> in the search API."]
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Performs a k-nearest neighbor (kNN) search and returns the matching documents.
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////
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[source,console]
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----
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PUT my-index
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{
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"mappings": {
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"properties": {
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"image_vector": {
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"type": "dense_vector",
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"dims": 3,
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"index": true,
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"similarity": "l2_norm"
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}
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}
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}
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}
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PUT my-index/_doc/1?refresh
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{
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"image_vector" : [0.5, 10, 6]
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}
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----
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////
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[source,console]
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----
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GET my-index/_knn_search
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{
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"knn": {
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"field": "image_vector",
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"query_vector": [0.3, 0.1, 1.2],
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"k": 10,
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"num_candidates": 100
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},
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"_source": ["name", "file_type"]
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}
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----
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// TEST[continued]
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// TEST[warning:The kNN search API has been replaced by the `knn` option in the search API.]
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[[knn-search-api-request]]
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==== {api-request-title}
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`GET <target>/_knn_search`
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`POST <target>/_knn_search`
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[[knn-search-api-prereqs]]
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==== {api-prereq-title}
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* If the {es} {security-features} are enabled, you must have the `read`
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<<privileges-list-indices,index privilege>> for the target data stream, index,
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or alias.
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[[knn-search-api-desc]]
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==== {api-description-title}
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The kNN search API performs a k-nearest neighbor (kNN) search on a
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<<dense-vector,`dense_vector`>> field. Given a query vector, it finds the _k_
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closest vectors and returns those documents as search hits.
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//tag::hnsw-algorithm[]
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{es} uses the https://arxiv.org/abs/1603.09320[HNSW algorithm] to support
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efficient kNN search. Like most kNN algorithms, HNSW is an approximate method
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that sacrifices result accuracy for improved search speed. This means the
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results returned are not always the true _k_ closest neighbors.
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//end::hnsw-algorithm[]
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The kNN search API supports restricting the search using a filter. The search
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will return the top `k` documents that also match the filter query.
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[[knn-search-api-path-params]]
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==== {api-path-parms-title}
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`<target>`::
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(Optional, string) Comma-separated list of data streams, indices, and aliases
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to search. Supports wildcards (`*`). To search all data streams and indices,
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use `*` or `_all`.
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[role="child_attributes"]
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[[knn-search-api-query-params]]
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==== {api-query-parms-title}
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include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=routing]
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[role="child_attributes"]
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[[knn-search-api-request-body]]
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==== {api-request-body-title}
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`filter`::
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(Optional, <<query-dsl,Query DSL object>>)
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include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=knn-filter]
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`knn`::
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(Required, object)
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include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=knn]
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+
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.Properties of `knn` object
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[%collapsible%open]
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====
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`field`::
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(Required, string)
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include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=knn-field]
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`k`::
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(Optional, integer)
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include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=knn-k]
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`num_candidates`::
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(Optional, integer)
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include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=knn-num-candidates]
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`query_vector`::
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(Required, array of floats or string)
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include::{es-ref-dir}/rest-api/common-parms.asciidoc[tag=knn-query-vector]
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====
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include::{es-ref-dir}/search/search.asciidoc[tag=docvalue-fields-def]
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include::{es-ref-dir}/search/search.asciidoc[tag=fields-param-def]
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include::{es-ref-dir}/search/search.asciidoc[tag=source-filtering-def]
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include::{es-ref-dir}/search/search.asciidoc[tag=stored-fields-def]
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[role="child_attributes"]
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[[knn-search-api-response-body]]
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==== {api-response-body-title}
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A kNN search response has the exact same structure as a
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<<search-api-response-body, search API response>>. However, certain sections
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have a meaning specific to kNN search:
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* The <<search-api-response-body-score,document `_score`>> is determined by
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the similarity between the query and document vector. See
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<<dense-vector-similarity, `similarity`>>.
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* The `hits.total` object contains the total number of nearest neighbor
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candidates considered, which is `num_candidates * num_shards`. The
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`hits.total.relation` will always be `eq`, indicating an exact value.
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