Understanding how nested types are stored in ES

[arsi]

Hi,

Let's say I have a nested type "points":

"points": [{x: 1, y: 1}, {x:5, y:3},...]

Why is it in that the following query works when I use the term points:

GET /mockindex/_search?size=5
{
    "query" : {
        "nested" : {
            "path" : "points",
            "query": {
                "exists" : { "field" : "points" }
            }
        }
    }
}

but when I do an aggregation query, using the term "points" doesn't work and I have to do points.x or points.y.

For example this query works:

{
    "aggregations" : {
        "nested_layer" : {
            "nested": {
                "path": "points"
            },
            "aggregations" : {
                "result" : {
                    "value_count": {"field": "points.x"}
                }
            }
        }
    }
}

and it will return the number of points I have (another way to think of it is that it will return the number of documents I have once Elasticsearch splits each nested type into its own document). However, if I replace points.x with just points, the query doesn't work anymore.

My question is this: if elasticsearch internally represents nested type "points" as "points.x" and "points.y" then how was the first query able to understand when I said "field": "points"? My second question is why am I not able to use "field": "points" in the aggregation query if I was able to use it in the first query? And lastly, is there a way I can write a value_count query so that it will return the number of documents that contain the field "points" and not the number internally represented documents where "points" are all separated out?