Elasticsearch filter on aggregation result (for search and aggregation) - elasticsearch

Question

Part of this question is related to : Elasticsearch filter on aggregation
Context
Let's say my Elasticsearch index contains some orders. Each order has one field price and one field amount. This result in an index that look like this :
[
{
"docKey": "order01",
"user": "1",
"price": 8,
"amount": 20
},
{
"docKey": "order02",
"user": "1",
"price": 14,
"amount": 3
},
{
"docKey": "order03",
"user": "2",
"price": 5,
"amount": 1
},
{
"docKey": "order04",
"user": "2",
"price": 10,
"amount": 3
}
]
What I would like to do
What I want to do is a filter on some values aggregated per user. I want to do this kind of filter for search and also in order to apply aggregation on it. For example in this example I would like to retrieve the documents of all user that have their average order with a price in the range of 9-14.
User 1 has an average price order of 11 so we keep both of his orders.
User 2 has an average price order of 7.5 so both his orders are not kept.
This was the easy part. After I filter to only get the user one. I want to do some more aggregates on the result.
So for example : I want the repartition of the average per user of the amout field among the bucket [0,10] and [10,20] for all user that have an average order with a price in the range of 9-14.
The answer I except for this question is 0 in the bucket [0,10] and one in the bucket [10,20] (Only user 1 is kept because of his average price. His average amount is 11.5 so in the bucket [10,20]).
What I have tried
I have manage do to my filter in order to retrieve the users that have their average order with a price in the range of 9-14. I did this by first doing a term aggregation on the user filed. Then I do a subaggregation that is an avg aggregation on the price. Then I do a bucket selector pipeline aggregation that check if the previous computed average price is between 9 and 14.
I have also manage to do the aggregation I wanted but without the previous filter. I did exactly the same thing that for the filter for each range. Then I count the number of results in each bucket.
I havn't find any way to apply an other aggregation on bucket selector result. So i could not first do the filter and then apply the range...
Also theses solution are not elegant.. I don't think they will scale up as a big part of the document need to be returned in the answer and processed further (even if it's off internet I prefer avoiding doing this and I might be limited in the result size of an aggregation ?).

Answer 1

I manage to find a solution but it's not elegant and might be poorly scalable.
Make a term aggregation on the user.
As a sub-aggregation of the term aggregation do an avg aggregation that compute the average of the price.
As a sub-aggregation of the term aggregation do an avg aggregation that compute the average of the amount.
Do a bucket selector pipeline aggregation that filter to only keep avg_price in range [9-14].
Do a bucket selector pipeline aggregation that filter to only keep avg_amount in a [0-10]
Do a "count" bucket script pipeline aggregation (with script returning one).
Do a bucket sum pipeline aggregation that sum the count.
Repeat all the steps for all ranges wanted ([0-10], [10-20])