Elasticsearch sort by dynamic price

Question

This is the scenario:

Imagine that a register user creates a new entity with the price: 1 | currency: EUR and other registered user creates a new entity with price: 1 | currency: USD and so on...

What I'm trying to do is sort by price the records depending on the currency selected by the frontend user (EUR or USD).

I can not index, for example price_eur or price_usd, because the rates change every hour, but if is possible, what is the best way to update the price for 10000 records?.

1 - Below are my suggestions, it works, but I think could be a better approach, any suggestion?

2 - If there is not, what will be the better performance approach?

3 - ES has some magic filed to play and used, for expample price_in_eur?

Function score

{
    "query": {
        "function_score": {
            "functions": [
                {
                    "script_score": {
                        // 1 EUR = 0.74452 USD
                        "script": "('EUR' == _source.currency ? doc['boat.price'].value : doc['boat.price'].value * 0.744520)"
                     }
                }
            ],
            "query": {
                "filtered": {
                    "query": { "match_all":{} }
                }
            }
        } 
    },
    "sort": { "_score": { "order": "desc" }}
}

Sort script

{
    "fields": ["_source"],
    "query": { "match_all": {} },  
    "sort": {
        "_script": {
            // 1 EUR = 0.74452 USD
            "script": "('EUR' == _source.currency ? doc['boat.price'].value : doc['boat.price'].value * 0.744520)",
            "type" : "number",
            "order": "asc"

        }
    }
}

Thanks for your time.

Answer 1

There is no direct way by which ES will do the price conversion for you automatically. The way you are doing is the correct way of accomplishing the task. You should go for a function score query since it'll be better compared to a single script based sorting. As the docs states:

Note, it is recommended, for single custom based script based sorting, to use function_score query instead as sorting based on score is faster.

Using a function score query will be better since sorting on a score value is faster.

Thanks