Elasticsearch OR query with nested objects returns inner_hits not matching the criteria - elasticsearch

Question

I'm getting weird results when querying nested objects. Imagine the following structure:
{ owner.name = "fred",
...,
pets [
{ name = "daisy", ... },
{ name = "flopsy", ... }
]
}
If I only have the document shown above, and I search pets matching this criteria:
pets.name = "daisy" OR
(owner.name = "julie" and pet.name = "flopsy")
I would expect to only get one result ("daisy"), but I'm getting both pet names.
This is one way to reproduce this:
# Create nested mapping
PUT pet-owners
{
"mappings": {
"animals": {
"properties": {
"owner": {"type": "text"},
"pets": {
"type": "nested",
"properties": {
"name": {"type": "text", "fielddata": true}
}
}
}
}
}
}
# Insert nested object
PUT pet-owners/animals/1?op_type=create
{
"owner" : "fred",
"pets" : [
{ "name" : "daisy"},
{ "name" : "flopsy"}
]
}
# Query
GET pet-owners/_search
{ "from": 0, "size": 50,
"query": {
"constant_score": {
"filter": { "bool": {"must": [
{"bool": {"should": [
{"nested": {"query":
{"term": {"pets.name": "daisy"}},
"path":"pets",
"inner_hits": {
"name": "pets_hits_1",
"size": 99,
"_source": false,
"docvalue_fields": ["pets.name"]
}
}},
{"bool": {"must": [
{"term": {"owner": "julie"}},
{"nested": {"query":
{"term": {"pets.name": "flopsy"}},
"path":"pets",
"inner_hits": {
"name": "pets_hits_2",
"size": 99,
"_source": false,
"docvalue_fields": ["pets.name"]
}
}}
]}}
]}}
]}}}},
"_source": false
}
The query returns both pets names (as opposed to the expected one).
Is this behavior normal? Am I doing something wrong, or my reasoning about the nested structure or the query behavior is flawed?
Any help or guidance will be much appreciated.
I'm running this query under ElasticSearch 6.3.x
EDIT: I'm adding the response received, to better illustrate the case
{
"took": 16,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"skipped": 0,
"failed": 0
},
"hits": {
"total": 1,
"max_score": 1,
"hits": [
{
"_index": "pet-owners",
"_type": "animals",
"_id": "1",
"_score": 1,
"inner_hits": {
"pets_hits_1": {
"hits": {
"total": 1,
"max_score": 0.6931472,
"hits": [
{
"_index": "pet-owners",
"_type": "animals",
"_id": "1",
"_nested": {
"field": "pets",
"offset": 0
},
"_score": 0.6931472,
"fields": {
"pets.name": [
"daisy"
]
}
}
]
}
},
"pets_hits_2": {
"hits": {
"total": 1,
"max_score": 0.6931472,
"hits": [
{
"_index": "pet-owners",
"_type": "animals",
"_id": "1",
"_nested": {
"field": "pets",
"offset": 1
},
"_score": 0.6931472,
"fields": {
"pets.name": [
"flopsy"
]
}
}
]
}
}
}
}
]
}
}
So we can see that it's not that the query matches and returns the whole existing document, but that it returns each of the pets independently, one inside each of the inner_hits. It's this result that's surprising to me.

Answer 1

(edited) - in summary this issue is around the context of the 'inner_hits':
It looks like the inner_hits 'pets_hits_2' is returning a match because it is belonging to the nested query that simply searches the pets field for 'flopsy'.
As an independent query on our single document, that is a valid hit.
However, because that query is within a list of bool/must queries, where other queries will not match on our document, you may well expect that the inner_hits should pick up on this and therefore not return a hit.
I haven't been able to find any docs to clarify whether this is intentional behaviour or not - might be worth raising with elastic ...