德鲁伊 sql 查询 - 对跨记录的多值字段进行明确计数

Question

Is there a way to do a distinct count across different rows for a multi-value field in druid SQL for a particular value in which value is only counted once across an array? eg suppose I have below records:

shippingSpeed 
[standard, standard, standard, ground]
[standard,ground]
[ground,ground]

Expected Result:

standard 2
ground 3

I tried below query but it is aggregating the field count inside an array and then giving the total count across all records:

SELECT
"shippingSpeed", count(*)
FROM orders
WHERE __time >= CURRENT_TIMESTAMP - INTERVAL '30' DAY
GROUP BY 1
ORDER BY 2 ASC

Result:

standard 4
ground 4

Answer 1

This is because the Group By on multi-valued columns will UNNEST the array into multiple rows. It is counting each item as an instance correctly.

If you want to remove duplicates, define "shippingSpeed" at ingestion time with the property: "multiValueHandling": "SORTED_SET"

You can find more details here: https://druid.apache.org/docs/latest/querying/multi-value-dimensions.html#overview