Array operation slow

SQL++
1

Hi,
I have table purchases with such structure:

SELECT VALUE a 
FROM purchases a
LIMIT 2

[
	{
		"type": "type_x",
		"customer": "c4211995-e113-4cf1-98cb-93bb06b5847e",
		"seller": "44ca450c-tim4-7856-boa3-d60ae9eb7ade",
		"price": 13
	},
	{
		"type": "type_x",
		"customer": "c4214985-e419-4cf1-98cb-93bb06b5847e",
		"seller": "44ca450c-ffb4-4626-b1a3-d60ae9eb7ade",
		"price": 12
	}
]

To speed up this query :

SELECT 
	customer, 
	seller,
	SUM(price),
	count(*)
FROM purchases
WHERE customer IS NOT MISSING
	and seller IS NOT MISSING
GROUP BY
	customer, 
	seller

I use such index :

CREATE INDEX adv_customer_seller_price ON `default`:`purchases`(`customer`,`seller`,`price`)

Without index query is completed in 16.1s, then with index it is completed in 358.2ms

Then there is a similar structure, only now data is in an array:

SELECT VALUE a 
FROM purchases_array a
LIMIT 2

[
	{
		"arr": [
			{
				"type": "type_x",
				"customer": "c4214985-e419-4cf1-98cb-93bb06b5847e",
				"seller": "44ca450c-ffb4-4626-b1a3-d60ae9eb7ade",
				"price": 12
			},
			{
				"type": "type_x",
				"customer": "c4214985-e419-4cf1-98cb-93bb06b5847e",
				"seller": "44ca450c-ffb4-4626-b1a3-d60ae9eb7ade",
				"price": 12
			}
		]
	},
	{
		"arr": [
			{
				"type": "type_x",
				"customer": "c4214985-e419-4cf1-98cb-93bb06b5847e",
				"seller": "44ca450c-ffb4-4626-b1a3-d60ae9eb7ade",
				"price": 12
			},
			{
				"type": "type_x",
				"customer": "c4214985-e419-4cf1-98cb-93bb06b5847e",
				"seller": "44ca450c-ffb4-4626-b1a3-d60ae9eb7ade",
				"price": 12
			}
		]
	}
]

I need to speed up this query:

SELECT a.customer,
       a.seller,
       SUM(a.price),
       COUNT(*)
FROM purchases_array p
UNNEST p.arr a
WHERE a.customer IS NOT MISSING
    and a.seller IS NOT MISSING
GROUP BY a.customer,
         a.seller

It runs in 8.2s without an index.

Index Advisor suggests such index:

CREATE INDEX adv_ALL_arr_seller_customer ON `default`:`purchases_array`(
	ALL ARRAY FLATTEN_KEYS(`a`.`seller`,`a`.`customer`) FOR a IN `arr` END
)

But this index did not speed up the query.

I also tried such index:

CREATE INDEX adv_ALL_arr_seller_customer ON `default`:`purchases_array`(
	ALL ARRAY FLATTEN_KEYS(`a`.`seller`,`a`.`customer`,`a`.`price`) FOR a IN `arr` END
)

with such query:


SELECT a.customer,
       a.seller,
       SUM(a.price),
       COUNT(*)
FROM purchases_array p
UNNEST p.arr a
WHERE a.customer IS NOT MISSING
    and a.seller IS NOT MISSING
    and a.price IS NOT MISSING
GROUP BY a.customer,
         a.seller

It didn’t help either.

Is there a way to speed up the query, and preferably as fast as in the case of an expanded structure (as in purchases)?