ElasticSearch - Getting paged result in a nested list (nested pagination) - elasticsearch

Question

I have the following Json that describes a country-city (1:n) relation
{
"country": [
{
"id": 1,
"name": "Country1",
"city": [
{"id": 1, "name": "City1"},
{"id": 2,"name": "City2"}
]
}, {
"id": 2,
"name": "Country2",
"city": [
{"id": 3,"name": "City3"},
{"id": 4,"name": "City4"}
]
}, {
"id": 3,
"name": "Country3",
"city": [
{"id": 5,"name": "City5"},
{"id": 6,"name": "City6"}
]
}
]
}
I have loaded it into an ES map with 3 documents of the three countries.
I have added nested property in the city index
...
"city": {
"type": "nested",
...
I want to query all cities and get a paged result.
For instance 3 hits will return city1, city2, city3
I want to filter by country name
I tried
GET /127.0.0.1:9200/country_city/_search
{
"from": 0,
"size": 2,
"fields": [
"city.id", "city.name"
]
}
and
GET /127.0.0.1:9200/country_city/country/_search?_source=false
{
"query": {
"nested": {
"path": "city",
"query": {
"match_all": {}
},
"inner_hits": {
"sort": "city.id",
"from": 0,
"size": 3
}
}
},
"fields": [
"name",
"city.id",
"city.name"
]
}
But the first returned two 4 cities instead of 2.
(2 countries have 2 cities each)
The second returned all documents(although size is 2 in the request) and in an inner element returned the first 3 cities of each country.
How Can I get a page size of the nested object?
And then progress to the next page?

Answer 1

This should work
Mappings
{
"mappings": {
"type": {
"properties": {
"country": {
"type": "nested",
"properties": {
"id": {
"type": "integer"
},
"name": {
"type": "text"
},
"city": {
"type": "nested",
"properties": {
"id": {
"type": "integer"
},
"name": {
"type": "keyword"
}
}
}
}
}
}
}
}
}
Query
{
"query": {
"nested": {
"path": "country",
"inner_hits": {},
"query": {
"nested": {
"path": "country.city",
"query": {
"match_all": {}
},
"inner_hits": {
"from": 0,
"size": 1,
"_source": {
"includes": ["country.city.name", "country.city.id"]
}
}
}
}
}
}
}
github bug
source filtering
Thanks