Group By Aggregation - database

Question

I have searched for similar questions and have not found a question that allows me to group the count of an attribute with another attribute.
I have a SQL Query in this format:
SELECT weight, COUNT(age)
FROM patient_table
GROUP BY weight
ORDER BY COUNT(age) DESC;
In an elastic search database I have this information:
{"height": 170, "weight": 200, "age": 18}, {"height": 180, "weight": 250, "age": 25},...
I want to translate this SQL query to a string query in elastic search. Therefore, I want the count of the age grouped by the weight and then to return the top value.
I do not know how to pass a select statement to the elastic search query, but I have figured out how to use terms aggregation to group by weight. I assume that I can just grab the top value after it has been ordered and this will be the answer I need.
This has been my attempt thus far:
GET /patient_table/_search
{
"aggs": {
"patient": {
"terms": {"field": "weight.keyword"},
"order": {"_count": "desc"}
}
}
}
EDIT: YD9's solution works, but is there anyway to create a max sub-aggregation to obtain the max value for the previous aggregations? I ask because when I try to create a sub-aggregation after the count, I get an incorrect value of null for the max_value. This is my attempt:
{
"size": 0,
"aggs": {
"weigth": {
"terms": {
"field": "weight.keyword",
"size": 10,
"order": {
"age_count_by_weight": "desc"
}
},
"aggs": {
"age_count_by_weight": {
"value_count": {"field": "age"}
}
}
}
},
"aggs": {
"max_age": {
"max": {"field": "age"}
}
}
}
Any help would be appreciated. Thank you in advance.

Answer 1

If you want to group by weight and order by the total number of ages for each weight, following query should work.
{
"size": 0,
"aggs": {
"weight": {
"terms": {
"field": "weight.keyword",
"size": 10,
"order": {
"age_count_by_weight": "desc"
}
},
"aggs": {
"age_count_by_weight": {
"cardinality": {
"field": "age"
}
}
}
}
}
}
Edit: cardinalty aggregations counts each age once. If you want to count total number of documents, this query should work:
"size": 0,
"aggs": {
"weigth": {
"terms": {
"field": "weight.keyword",
"size": 10,
"order": {
"age_count_by_weight": "desc"
}
},
"aggs": {
"age_count_by_weight": {
"value_count": {
"field": "age"
}
}
}
}
}
}
Edit 2: To get max of age, you can use max_buckets aggregation. This is the sample query
{
"size": 0,
"aggs": {
"weigth": {
"terms": {
"field": "weight.keyword",
"size": 10,
"order": {
"age_count_by_weight": "desc"
}
},
"aggs": {
"age_count_by_weight": {
"value_count": {
"field": "age"
}
}
}
},
"max_age": {
"max_bucket": {
"buckets_path": "weigth>age_count_by_weight"
}
}
}
}