Elastic search top_hits aggregation on nested - elasticsearch

Question

I have an index which contains CustomerProfile documents. Each of this document in the CustomerInsightTargets(with the properties Source,Value) property can be an array with x items. What I am trying to achieve is an autocomplete (of top 5) on CustomerInsightTargets.Value grouped by CustomerInisghtTarget.Source.
It will be helpful if anyone gives me hint about how to select only a subset of nested objects from each document and use that nested obj in aggregations.
{
"customerinsights": {
"aliases": {},
"mappings": {
"customerprofile": {
"properties": {
"CreatedById": {
"type": "long"
},
"CreatedDateTime": {
"type": "date"
},
"CustomerInsightTargets": {
"type": "nested",
"properties": {
"CustomerInsightSource": {
"type": "text",
"fields": {
"keyword": {
"type": "keyword",
"ignore_above": 256
}
}
},
"CustomerInsightValue": {
"type": "text",
"term_vector": "yes",
"fields": {
"keyword": {
"type": "keyword",
"ignore_above": 256
}
},
"analyzer": "ngram_tokenizer_analyzer"
},
"CustomerProfileId": {
"type": "long"
},
"Guid": {
"type": "text",
"fields": {
"keyword": {
"type": "keyword",
"ignore_above": 256
}
}
},
"Id": {
"type": "long"
}
}
},
"DisplayName": {
"type": "text",
"term_vector": "yes",
"analyzer": "ngram_tokenizer_analyzer"
},
"Email": {
"type": "text",
"fields": {
"keyword": {
"type": "keyword",
"ignore_above": 256
}
}
},
"Id": {
"type": "long"
},
"ImageUrl": {
"type": "text",
"fields": {
"keyword": {
"type": "keyword",
"ignore_above": 256
}
}
}
}
}
},
"settings": {
"index": {
"number_of_shards": "1",
"provided_name": "customerinsights",
"creation_date": "1484860145041",
"analysis": {
"analyzer": {
"ngram_tokenizer_analyzer": {
"type": "custom",
"tokenizer": "ngram_tokenizer"
}
},
"tokenizer": {
"ngram_tokenizer": {
"type": "nGram",
"min_gram": "1",
"max_gram": "10"
}
}
},
"number_of_replicas": "2",
"uuid": "nOyI0O2cTO2JOFvqIoE8JQ",
"version": {
"created": "5010199"
}
}
}
}
}
Having as example a document:
{
{
"Id": 9072856,
"CreatedDateTime": "2017-01-12T11:26:58.413Z",
"CreatedById": 9108469,
"DisplayName": "valentinos",
"Email": "valentinos#mail.com",
"CustomerInsightTargets": [
{
"Id": 160,
"CustomerProfileId": 9072856,
"CustomerInsightSource": "Tags",
"CustomerInsightValue": "Tag1",
"Guid": "00000000-0000-0000-0000-000000000000"
},
{
"Id": 160,
"CustomerProfileId": 9072856,
"CustomerInsightSource": "ProfileName",
"CustomerInsightValue": "valentinos",
"Guid": "00000000-0000-0000-0000-000000000000"
},
{
"Id": 160,
"CustomerProfileId": 9072856,
"CustomerInsightSource": "Playground",
"CustomerInsightValue": "Wiki",
"Guid": "00000000-0000-0000-0000-000000000000"
}
]
}
}
If i ran an aggregation on the top_hits the result will include all targets from a document -> if one of them match my search text.
Example
GET customerinsights/_search
{
"query": {
"bool": {
"must": [
{
"nested": {
"path": "CustomerInsightTargets",
"query": {
"bool": {
"must": [
{
"match": {
"CustomerInsightTargets.CustomerInsightValue": {
"query": "2017",
"operator": "AND",
"fuzziness": 2
}
}
}
]
}
}
}
}
]
}
} ,
"aggs": {
"root": {
"nested": {
"path": "CustomerInsightTargets"
},
"aggs": {
"top_tags": {
"terms": {
"field": "CustomerInsightTargets.CustomerInsightSource.keyword"
},
"aggs": {
"top_tag_hits": {
"top_hits": {
"sort": [
{
"_score": {
"order": "desc"
}
}
],
"size": 5,
"_source": "CustomerInsightTargets"
}
}
}
}
}
}
},
"size": 0,
"_source": "CustomerInsightTargets"
}
My question is how I should use the aggregation to get the "autocomplete" Values grouped by Source and order by the _score. I tried to use a significant_terms aggregation but doesn't work so well, also terms aggs doesn't sort by score (and by _count) and having fuzzy also adds complexity.