Couchbase N1QL query aggregation - json

Question

I'm trying to write a query that will aggregate the results of a query to provide total values for the results matched.
The documents in the bucket look like this:
{
"clientId": "test-client",
"event": {
"history": [
{
"code": "FAILED",
"serviceId": "s1"
},
{
"code": "SUCCESS",
"serviceId": "s2"
}
],
"size": 200
}
},
{
"clientId": "test-client",
"event": {
"history": [
{
"code": "FAILED",
"serviceId": "s1"
},
{
"code": "SUCCESS",
"serviceId": "s2"
}
],
"size": 200
}
},
{
"clientId": "test-client",
"event": {
"history": [
{
"code": "SUCCESS",
"serviceId": "s1"
}
],
"size": 200
}
}
The output document I'm looking to produce looks like this:
{
"clientId": "test-client",
"totalSize": 600,
"totalVolume": 3,
"serviceSummary": [
{
"serviceId": "s1",
"serviceTotalSize": 200,
"serviceTotalVolume": 1
},
{
"serviceId": "s2",
"serviceTotalSize": 400,
"serviceTotalVolume": 2
}
]
}
So the query needs to
aggregate all results for the clientId calculating totalSize and totalVolume
look at the content of the history array, and find the serviceId with a code of "SUCCESS"
provide a total size and volume for the serivceId where the event was successful
So far I have a query like this:
select
d.clientId,
count(*) totalVolume,
sum(d.event.size) totalSize ,
ARRAY_AGG(DISTINCT h.serviceId) serviceSummary
from demo d
unnest d.event.history h
where h.code = 'SUCCESS'
group by d.clientId;
which produces part of the result I want, but not the full serviceSummary
thanks for any help.

Answer 1

SQL standards doesn't allow nested aggregates you need intervening subquery with multi level aggregates.
SELECT d1.clientId,
SUM(d1.serviceTotalVolume) AS totalVolume,
SUM(d1.serviceTotalSize) AS totalSize,
ARRAY_AGG({d1.serviceId, d1.serviceTotalVolume, d1.serviceTotalSize}) AS serviceSummary
FROM ( SELECT
d.clientId,
h.serviceId,
COUNT(1) AS serviceTotalVolume,
SUM(d.event.size) AS serviceTotalSize
FROM demo AS d
UNNEST d.event.history AS h
WHERE h.code = 'SUCCESS'
GROUP BY d.clientId, h.serviceId) AS d1
GROUP BY d1.clientId;