I am trying to change object type to nested by
PUT lfx2_lp_prices1/_mapping
{
    "properties" : {
        "NoMDEntries" : {"type" : "nested"}
    }
}
But getting error
"type": "illegal_argument_exception",
"reason": "object mapping [NoMDEntries] can't be changed from non-nested to nested"
NoMDEntries in arrany of some currency prices.