Using multiple similarity metrics on an existing index

[mkaze]

I was wondering if it's possible to use multiple similarity metrics for an index in Elasticsearch. Let's assume I have already defined an index with a customized BM25 similarity metric (say, with b=1), and now I would like to add another similarity metric (say, BM25 with b=0) to this index. Is this possible? If so, does this imply a re-index? Unfortunately I couldn't find any examples in documentation or elsewhere which uses multiple similarity metrics for the same index; so I was in doubt if this is possible at all?!

Example scenario:

"index": {
    "similarity": {
        "BM25_v1": {
            "type": "BM25",
            "b": 1.0
        },
        # add a new metric on this index.
        "BM25_v2": {
            "type": "BM25",
            "b": 0.0
        }
    }
}

And its usage:

{
    'some_field': {
        'type': 'text',
        'norms': 'true',
        'similarity': 'BM25_v1'  # old metric
    },
    'another_field': {
        'type': 'text',
        'norms': 'true',
        'similarity': 'BM25_v2'  # new metric
    },
}