Ggtcf

I have a Postgresql table with a json column named "food".

Here is an example of some rows:

food
["cheese", "salmon", "eggs"]
["salmon", "cheese", "eggs"]
["broccoli", "ham", "milk"]
["salmon", "cheese", "eggs", "pizza"]

Current result:

food count
["cheese", "salmon", "eggs"] | 1
["salmon", "cheese", "eggs"] | 1
["broccoli", "ham", "milk"] | 1
["salmon", "cheese", "eggs", "pizza"] | 1

Desired result:

food count
["cheese", "salmon", "eggs"] | 2
["broccoli", "ham", "milk"] | 1
["salmon", "cheese", "eggs", "pizza"] | 1

Is there a way to GROUP BY the contents of a json field without regard to the order of the elements? If two rows have the same exact contents, then I want them to be grouped together.

My plan was to GROUP BY json_array_elements(food), but for some reason this only returns the first element of each row.

Actually similar to the answer of @Scoots, but no sorts, windows, aso:

SELECT (
 SELECT jsonb_agg(items order by items)
 FROM jsonb_array_elements(food) AS items
 ) AS food,
 count(*)
FROM test_json_grouping
GROUP BY 1;

...explained:

 QUERY PLAN 
------------------------------------------------------------------------------------------------------
 HashAggregate (cost=1635.60..1890.60 rows=200 width=40)
 Group Key: (SubPlan 1)
 -> Seq Scan on test_json_grouping (cost=0.00..1629.25 rows=1270 width=32)
 SubPlan 1
 -> Aggregate (cost=1.25..1.26 rows=1 width=32)
 -> Function Scan on jsonb_array_elements items (cost=0.00..1.00 rows=100 width=32)
(6 rows)

Result:

 food | count 
---------------------------------------+-------
 ["cheese", "eggs", "salmon"] | 2
 ["broccoli", "ham", "milk"] | 1
 ["cheese", "eggs", "pizza", "salmon"] | 1
(3 rows)

Not directly - to Postgres they're different strings.

However what we can do is unpack these json strings through json_array_elements, then repack them with our own sorting applied with json_agg. They're then homogenized for your group by to work.

Here's a query illustrating exactly what I mean:

select
 __food.food::text,
 count(1)
from (
 select
 json_agg(_unpack.food order by _unpack.food::text asc) as food
 from (
 select
 row_number() over(),
 json_array_elements(food) as food
 from
 YOUR_SCHEMA.YOUR_FOOD_TABLE
 ) as _unpack
 group by
 _unpack.row_number
) as __food
group by
 __food.food::text