ElasticSearch - Filtering a result and manipulating the documents - elasticsearch

Question

I have the following query - which works fine (this might not be the actual query):
{
"query": {
"bool": {
"must": [
{
"nested": {
"path": "location",
"query": {
"geo_distance": {
"distance": "16090km",
"distance_type": "arc",
"location.point": {
"lat": "51.794177",
"lon": "-0.063055"
}
}
}
}
},
{
"geo_distance": {
"distance": "16090km",
"distance_type": "arc",
"location.point": {
"lat": "51.794177",
"lon": "-0.063055"
}
}
}
]
}
}
}
Although I want to do the following (as part of the query but not affecting the existing query):
Find all documents that have field_name = 1
On all documents that have field_name = 1 run ordering by geo_distance
Remove duplicates that have field_name = 1 and the same value under field_name_2 = 2 and leave the closest item in the documents result, but remove the rest
Update (further explanation):
Aggregations can't be used as we want to manipulate the documents in the result.
Whilst also maintaining the order within the documents; meaning:
If I have 20 documents, sorted by a field; and I have 5 of which have field_name = 1, I would like to sort the 5 by distance, and eliminate 4 of them; whilst still maintaining the first sort. (possibly doing the geodistance sort and elimination before the actual query?)
Not too sure how to do this, any help is appreciated - I'm currently using ElasticSearch DSL DRF - but I can easily convert the query to ElasticSearch DSL.
Example documents (before manipulation):
[{
"field_name": 1,
"field_name_2": 2,
"location": ....
},
{
"field_name": 1,
"field_name_2": 2,
"location": ....
},
{
"field_name": 55,
"field_name_5": 22,
"location": ....
}]
Output (Desired):
[{
"field_name": 1,
"field_name_2": 2,
"location": .... <- closest
},
{
"field_name": 55,
"field_name_5": 22,
"location": ....
}]

Answer 1

One way to achieve what you want is to keep the query part as you have it now (so you still get the hits you need) and add an aggregation part in order to get the closest document with an additional condition on filed_name. The aggregation part would be made of:
a filter aggregation to only consider the documents with field_name = 1
a geo_distance aggregation with a very small distance
a top_hits aggregation to return the document with the closest distance
The aggregation part would look like this:
{
"query": {
...same as you have now...
},
"aggs": {
"field_name": {
"filter": {
"term": {
"field_name": 1 <--- only select desired documents
}
},
"aggs": {
"geo_distance": {
"field": "location.point",
"unit": "km",
"distance_type": "arc",
"origin": {
"lat": "51.794177",
"lon": "-0.063055"
},
"ranges": [
{
"to": 1 <---- single bucket for docs < 1km (change as needed)
}
]
},
"aggs": {
"closest": {
"top_hits": {
"size": 1, <---- closest document
"sort": [
{
"_geo_distance": {
"location.point": {
"lat": "51.794177",
"lon": "-0.063055"
},
"order": "asc",
"unit": "km",
"mode": "min",
"distance_type": "arc",
"ignore_unmapped": true
}
}
]
}
}
}
}
}
}
}

Answer 2

This can be done using Field Collapsing - which is the equivalent of grouping. - Below is an example of how this can be achieved:
{"collapse": {"field": "vin",
"inner_hits": {
"name": "closest_dealer",
"size": 1,
"sort": [
{
"_geo_distance": {
"location.point": {
"lat": "latitude",
"lon": "longitude"
},
"order": "desc",
"unit": "km",
"distance_type": "arc",
"nested_path": "location"
}
}
]
}
}
}
The collapsing is done on the field vin - and the inner_hits is used to sort the grouped items and get the closest one. (size = 1)