PostgreSQL how to merge jsonb keys and count values - postgresql

Question

I have a table that looks somthing like the following:
id
name
category
specs (jsonb)
1
product1
phones
{ "brand": "brand1", "color": "red", "size": 5, "memory": "8GB"}
2
product2
phones
{ "brand": "brand1", "color": "white", "size": 7, "memory": "8GB"}
3
product3
laptops
{ "brand": "brand20", "storage": "SSD", "os": "os1" , "memory": "32GB"}
My desired output given a specific category
{
"brand": {
"brand1": 1,
"brand2": 1
},
"color": {
"red": 1,
"white": 5,
},
"memory": {
"8gb": 2,
}
}

Answer 1

Blow out the specs column with jsonb_each_text(), calculate the counts, and then reassemble with jsonb_object_agg() (the first two CTEs could be combined into one, but I left them verbose for illustration):
with blowout as (
select s.category, j.key, j.value
from somthing s
cross join lateral jsonb_each_text(s.specs) as j(key, value)
), counts as (
select category, key, value, count(1) as cnt
from blowout
group by category, key, value
), agg_specs as (
select category, key, jsonb_object_agg(value, cnt) as counts
from counts
group by category, key
)
select category, jsonb_object_agg(key, counts) as output
from agg_specs
group by category
;
db<>fiddle here