How to search data with a 'knn query'?

[gengdeyin]

Please use the following questions as a guideline to help me answer your issue/question without further inquiry. Thank you.

Which version of Elastic are you using?

[✔️] elastic.v7 (for Elasticsearch 7.x) [ ] elastic.v6 (for Elasticsearch 6.x) [ ] elastic.v5 (for Elasticsearch 5.x) [ ] elastic.v3 (for Elasticsearch 2.x) [ ] elastic.v2 (for Elasticsearch 1.x)

Please describe the expected behavior

How to search data with a 'knn query'? just like the curl cmd: curl --location 'http://{ip}:{port}/{vector_index}/_search?username=uanme&password=pwd'
--header 'Content-Type: application/json'
--data '{ "query": { "knn": { "vector": { "vector": {vector}, "k": 2, "ef": 100 } } }, "size": 10 }'

Please describe the actual behavior

Any steps to reproduce the behavior?