This documentation contains work-in-progress information for future Elastic Stack and Cloud releases. Use the version selector to view supported release docs. It also contains some Elastic Cloud serverless information. Check out our serverless docs for more details.
similarity
editsimilarity
editElasticsearch allows you to configure a text scoring algorithm or similarity
per field. The similarity setting provides a simple way of choosing a
text similarity algorithm other than the default BM25, such as boolean.
Only text-based field types like text and keyword
support this configuration.
Custom similarities can be configured by tuning the parameters of the built-in similarities. For more details about this expert options, see the similarity module.
The only similarities which can be used out of the box, without any further configuration are:
-
BM25 - The Okapi BM25 algorithm. The algorithm used by default in Elasticsearch and Lucene.
-
boolean - A simple boolean similarity, which is used when full-text ranking is not needed and the score should only be based on whether the query terms match or not. Boolean similarity gives terms a score equal to their query boost.
The similarity can be set on the field level when a field is first created,
as follows:
resp = client.indices.create(
index="my-index-000001",
mappings={
"properties": {
"default_field": {
"type": "text"
},
"boolean_sim_field": {
"type": "text",
"similarity": "boolean"
}
}
},
)
print(resp)
response = client.indices.create(
index: 'my-index-000001',
body: {
mappings: {
properties: {
default_field: {
type: 'text'
},
boolean_sim_field: {
type: 'text',
similarity: 'boolean'
}
}
}
}
)
puts response
const response = await client.indices.create({
index: "my-index-000001",
mappings: {
properties: {
default_field: {
type: "text",
},
boolean_sim_field: {
type: "text",
similarity: "boolean",
},
},
},
});
console.log(response);