If the name is not specified, even though the engine is known to be faiss, I couldn't determine which algorithm is used by default

OpenSearch
1

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Describe the issue:
I forgot setting the params “method” when I created field of knn_vector,and I couldn’t know whether engine use brute force or not from the documentation.
In my staging Opensearch enviroment, the knn_vector was so slow,and I want to know which algorithm used in knn search.
Sorry for my poor English.

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