Hi,
I am new to Elasticsearch and I am having troubles with the Nest/Elastic.Net library.
I would like to retrieve not entire document but just part of it. I am able to do it in Postman but I cannot do it via Elastic.Net library or Nest library.
Document structure looks like following
{
“Doc_id”: “id_for_cross_refference_with_othersystem”
“Ocr”:[
{
“word”: “example_word1”,
“box”: [],
“cord”: “some_number”,
},
{
“word”: “example_word2”,
“box”: [],
“cord”: “some_number2”,
}
]
}
The document has a huge amount of properties but I am interested only in Doc_id , ocr.word, ocr.box and ocr.cord
The following postman request fully satisfies my needs 
{
"query": {
"bool": {
"must": [
{
"match": {
"doc_id": "2a558865-7dc2-4e4d-ad02-3f683159984e"
}
},
{
"nested": {
"path": "ocr",
"query": {
"match": {
"ocr.word": "signing"
}
},
"inner_hits": {
"_source": {
"includes":[
"ocr.word",
"ocr.box",
"ocr.conf"
]
}
}
}
}
]
}
},
"_source":"false"
}
Result of that request is following
{
"took": 9,
"timed_out": false,
"_shards": {
"total": 1,
"successful": 1,
"skipped": 0,
"failed": 0
},
"hits": {
"total": {
"value": 3,
"relation": "eq"
},
"max_score": 18.99095,
"hits": [
{
"_index": "irrelevant",
"_type": "irrelevant",
"_id": "irrelevant",
"_score": 18.99095,
"_source": {},
"inner_hits": {
"ocr": {
"hits": {
"total": {
"value": 1,
"relation": "eq"
},
"max_score": 7.9260864,
"hits": [
{
"_index": "irrelevant",
"_type": "irrelevant",
"_id": "irrelevant",
"_nested": {
"field": "ocr",
"offset": 11
},
"_score": 7.9260864,
"_source": {
"box": [
],
"conf": "96.452858",
"word": "signing"
}
}
]
}
}
}
},
{
"_index": "there_rest _of_object_is_ommited",
},
{
"_index": "there_rest _of_object_is_ommited",
}
]
}
}
However when I try to convert that request to Nest Query DSL I am not able to achieve the same result.
When I try to use the NEST library I don’t see any way to provide output result model/type. It looks like the Type of Document should match the output type which is not my case.
Query that I am using :
var searchResponse = client2.Search<Model>(s => s
.Query(q1 => q1.Bool(b1 => b1.Must(s1 =>
s1.Match(m => m.Field(f => f.doc_id).Query("2a558865-7dc2-4e4d-ad02-3f683159984e")),
s2 => s2.Nested(n => n.Path("ocr").Query(q2 => q2.Bool(b => b.Must(m => m.Match(m => m.Field(f => f.ocr.First().word).Query("signing")))))
.InnerHits(ih => ih.Source(s => s.Includes(i => i.Field(f => f.ocr.First().word).Field(f => f.ocr.First().conf))))
)
)))
.Source(false)
);
Due to the fact that the Model type is created for a document and it doesn’t match the output type I am getting [null, null, null] as the output .
There is property such properties as Hits in ISearchResponse? But when I look into it I cannot see values of fields.
I tried using a low level client (Elastic.Net) and providing json request as a string. But It looks like there is not way of specifying the output type either. When I ran my code with the low level library it returns me 3 object of class Model with empty fields.
My questions are :
- Is it possible to specify output type different from document type for Nest query DSL or Elatic.Net library ?
- Is it possible to get values of the fields that I specified in the request for inner hits with help of Nest or Elastic.Net libraries?
- How would you solve such problem ? I mean we have huge documents and we don’t want to pass unnecessary information back and forth. The inner hits approach looks like a neat solution for us but it doesn’t look like it works with the recommended libraries Unless I am doing some silly mistake.
NOTE: I can achieve desired result with simple use of HTTPClient and manually doing what I need , but I hope to leverage library that is written for this purpose(Nest or Elastic.Net).