# Filter by minimum value per parent (or term)

**URL:** <https://discuss.elastic.co/t/filter-by-minimum-value-per-parent-or-term/15751>\
**Category:** Elasticsearch\
**Created:** [February 12, 2014, 10:03am UTC](https://discuss.elastic.co/t/filter-by-minimum-value-per-parent-or-term/15751 "2014-02-12T10:03:19Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Manuel\_Brunner](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@Manuel\_Brunner](https://discuss.elastic.co/u/Manuel_Brunner)\
**Post date:** [February 12, 2014, 10:03am UTC](https://discuss.elastic.co/t/filter-by-minimum-value-per-parent-or-term/15751/1 "2014-02-12T10:03:19Z")

</div>

Use Case

- Hotels (~some thousand) with Offers (~some million)
- Hotels and offers each have a lot of data where filters are applied
- Sorting needs to be done by minimum offer price or some other ratings
- Need to retrieve the cheapest offer per hotel (while matching all  
hotel and offer filters)

I have modeled it so that hotels are parents of offers.

Approaches:

1. Use a has\_child filter to get all hotels which have at least one  
matching offer. I think I could even get the minimum price with a  
top\_children query and custom\_score, but I still don't know which offer was  
the cheapest.
2. Use a has\_parent filter to get all offers, which match offer and  
hotel filters.

With approach 2 I could filter the cheapest offer in the application, but I  
would have to retrieve all matching offers from elasticsearch and would  
lose all pagination and sorting capabilities and lose quite some  
performance, if there are a lot of matches.

Here is a simplified example. Offers 1 and 2 are returned, but I need to  
return only the cheapest one per hotel (offer 2). Is there any possibility  
to achieve this?

#!/bin/sh

curl -XPUT '[http://localhost:9200/test](http://localhost:9200/test)' -d '{  
"mappings": {  
"offer": {  
"\_parent": {  
"type": "hotel"  
}  
},  
"hotel": {  
"properties": {  
"country": {  
"type": "string",  
"index": "not\_analyzed"  
}  
}  
}  
}  
}'

echo

curl -XPUT '[http://localhost:9200/test/hotel/1](http://localhost:9200/test/hotel/1)' -d '{  
"country" : "AT"  
}'

echo

curl -XPUT '[http://localhost:9200/test/hotel/2](http://localhost:9200/test/hotel/2)' -d '{  
"country" : "DE"  
}'

echo

curl -XPUT '[http://localhost:9200/test/offer/1?parent=1](http://localhost:9200/test/offer/1?parent=1)' -d '{  
"arrival": "2015-01-01",  
"price": "100"  
}'

echo

curl -XPUT '[http://localhost:9200/test/offer/2?parent=1](http://localhost:9200/test/offer/2?parent=1)' -d '{  
"arrival" : "2015-01-01",  
"price" : "90"  
}'

echo

curl -XPUT '[http://localhost:9200/test/offer/3?parent=1](http://localhost:9200/test/offer/3?parent=1)' -d '{  
"arrival" : "2015-01-02",  
"price" : "80"  
}'

echo

curl -XPUT '[http://localhost:9200/test/offer/4?parent=2](http://localhost:9200/test/offer/4?parent=2)' -d '{  
"arrival": "2015-01-01",  
"price": "100"  
}'

echo  
sleep 1

curl -XGET '[http://localhost:9200/test/offer/\_search](http://localhost:9200/test/offer/_search)' -d '{  
"query": {  
"filtered": {  
"filter": {  
"bool": {  
"must": {  
"term": {  
"arrival": "2015-01-01"  
}  
},  
"must": {  
"has\_parent": {  
"type": "hotel",  
"filter": {  
"term" : {"country" : "AT" }

```
                    }
                  }
              }
            }
        }
    }
}

```

}'  
echo

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---

<div class="post-metadata">

**Author:** ![Manuel\_Brunner](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@Manuel\_Brunner](https://discuss.elastic.co/u/Manuel_Brunner)\
**Post date:** [April 23, 2014, 1:54pm UTC](https://discuss.elastic.co/t/filter-by-minimum-value-per-parent-or-term/15751/2 "2014-04-23T13:54:44Z")

</div>

With aggregations in the new elasticsearch version I came up with a  
solution to get the cheapest offer per hotel:

> <https://gist.github.com/manuelbrunner/11215712>

However, it returns just the bucket key and the value:  
"buckets" : [ {  
"key" : "h1",  
"doc\_count" : 2,  
"min\_price" : {  
"value" : 90.0  
}  
}

I cannot see which of the offers has this minimum price.

Does anyone have a solution for this problem? I'm not sure if Elasticsearch  
is really a good fit for our use case and I might want to have a look at  
MongoDB.

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---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [July 6, 2017, 1:34am UTC](https://discuss.elastic.co/t/filter-by-minimum-value-per-parent-or-term/15751/3 "2017-07-06T01:34:05Z")

</div>