ElasticSearch _parent query - elasticsearch

Question

Elastic documentation states that one can use the _parent field in a query (see https://www.elastic.co/guide/en/elasticsearch/reference/current/mapping-parent-field.html).
However, I have been unable to get it to work. Here's the simple test:
PUT /company
{
"mappings": {
"branch": {},
"employee": {
"_parent": {
"type": "branch"
}
}
}
}
POST /company/branch/_bulk
{ "index": { "_id": "london" }}
{ "name": "London Westminster", "city": "London", "country": "UK" }
{ "index": { "_id": "liverpool" }}
{ "name": "Liverpool Central", "city": "Liverpool", "country": "UK" }
{ "index": { "_id": "paris" }}
{ "name": "Champs Élysées", "city": "Paris", "country": "France" }
PUT /company/employee/1?parent=london
{
"name": "Alice Smith",
"dob": "1970-10-24",
"hobby": "hiking"
}
Verifying that the employees have a _parent field:
GET /company/employee/_search
{
"query": {
"match_all": {}
}
}
returns
{
"took": 1,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 1,
"max_score": 1,
"hits": [
{
"_index": "company",
"_type": "employee",
"_id": "1",
"_score": 1,
"_routing": "london",
"_parent": "london",
"_source": {
"name": "Alice Smith",
"dob": "1970-10-24",
"hobby": "hiking"
}
}
]
}
}
But the following:
GET /company/employee/_search
{
"query": {
"term": {
"_parent":"london"
}
}
}
returns:
{
"took": 1,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 0,
"max_score": null,
"hits": []
}
}
Using "has_parent" works, but why doesn't using _parent work, as stated in the docs.
Here's the query using has_parent that works:
GET /company/employee/_search
{
"query": {
"has_parent": {
"parent_type":"branch",
"query":{
"match_all": {}
}
}
}
}
What am I missing? Using ElasticSearch 5.0.2.

Answer 1

It's a documentation bug. According to the breaking changes in 5.0, the _parent field is no longer indexed and hence it is not possible to run a term query on that field. You either need to use the has_parent query or the new parent_id query to find that child document:
POST /company/employee/_search
{
"query": {
"parent_id": {
"type": "employee",
"id": "london"
}
}
}
For those who want to follow, I've filed an issue to report this and it got fixed. The updated documentation will soon be available.