61 lines
3.3 KiB
Markdown
61 lines
3.3 KiB
Markdown
---
|
|
layout: default
|
|
title: k-NN Index
|
|
nav_order: 1
|
|
parent: k-NN
|
|
has_children: false
|
|
redirect_from: /docs/knn/knn-index/
|
|
---
|
|
|
|
# k-NN Index
|
|
|
|
## knn_vector data type
|
|
|
|
The k-NN plugin introduces a custom data type, the `knn_vector`, that allows users to ingest their k-NN vectors
|
|
into an OpenSearch index.
|
|
|
|
```json
|
|
"my_vector": {
|
|
"type": "knn_vector",
|
|
"dimension": 4,
|
|
"method": {
|
|
"name": "hnsw",
|
|
"space_type": "l2",
|
|
"engine": "nmslib",
|
|
"parameters": {
|
|
"ef_construction": 128,
|
|
"m": 24
|
|
}
|
|
}
|
|
}
|
|
```
|
|
|
|
Mapping Pararameter | Required | Default | Updateable | Description
|
|
:--- | :--- | :--- | :--- | :---
|
|
`type` | true | n/a | false | The type of the field
|
|
`dimension` | true | n/a | false | The vector dimension for the field
|
|
`method` | false | null | false | The configuration for the Approximate nearest neighbor method
|
|
`method.name` | true, if `method` is specified | n/a | false | The identifier for the nearest neighbor method. Currently, "hnsw" is the only valid method.
|
|
`method.space_type` | false | "l2" | false | The vector space used to calculate the distance between vectors. Refer to [here]({{site.url}}{{site.baseurl}}/search-plugins/knn/approximate-knn#spaces)) to see available spaces.
|
|
`method.engine` | false | "nmslib" | false | The approximate k-NN library to use for indexing and search. Currently, "nmslib" is the only valid engine.
|
|
`method.parameters` | false | null | false | The parameters used for the nearest neighbor method.
|
|
`method.parameters.ef_construction` | false | 512 | false | The size of the dynamic list used during k-NN graph creation. Higher values lead to a more accurate graph, but slower indexing speed. Only valid for "hnsw" method.
|
|
`method.parameters.m` | false | 16 | false | The number of bidirectional links that the plugin creates for each new element. Increasing and decreasing this value can have a large impact on memory consumption. Keep this value between 2-100. Only valid for "hnsw" method
|
|
|
|
## Index settings
|
|
|
|
Additionally, the k-NN plugin introduces several index settings that can be used to configure the k-NN structure as well.
|
|
|
|
At the moment, several parameters defined in the settings are in the deprecation process. Those parameters should be set
|
|
in the mapping instead of the index settings. Parameters set in the mapping will override the parameters set in the
|
|
index settings. Setting the parameters in the mapping allows an index to have multiple `knn_vector` fields with
|
|
different parameters.
|
|
|
|
Setting | Default | Updateable | Description
|
|
:--- | :--- | :--- | :---
|
|
`index.knn` | false | false | Whether the index should build hnsw graphs for the `knn_vector` fields. If set to false, the `knn_vector` fields will be stored in doc values, but Approximate k-NN search functionality will be disabled.
|
|
`index.knn.algo_param.ef_search` | 512 | true | The size of the dynamic list used during k-NN searches. Higher values lead to more accurate but slower searches.
|
|
`index.knn.algo_param.ef_construction` | 512 | false | (Deprecated in 1.0.0. Use the mapping parameters to set this value instead.) Refer to mapping definition.
|
|
`index.knn.algo_param.m` | 16 | false | (Deprecated in 1.0.0. Use the mapping parameters to set this value instead.) Refer to mapping definition.
|
|
`index.knn.space_type` | "l2" | false | (Deprecated in 1.0.0. Use the mapping parameters to set this value instead.) Refer to mapping definition.
|