Aggregate jsonb map with string array as value in postgresql - sql

Question

I have postgresql table with a jsonb column containing maps with strings as keys and string arrays as values. I want to aggregate all the maps into a single jsonb map. There should be no duplicate values in string array. How can I do this in postgres.
Eg:
Input: {"a": ["1", "2"]}, {"a": ["2", "3"], "b": ["5"]}
Output: {"a": ["1", "2", "3"], "b": ["5"]}
I tried '||' operator but it overwrites values if there as same keys in maps.
Eg:
Input: SELECT '{"a": ["1", "2"]}'::jsonb || '{"a": ["3"], "b": ["5"]}'::jsonb;
Output: {"a": ["3"], "b": ["5"]}

Answer 1

Using jsonb_object_agg with a series of cross joins:
select jsonb_object_agg(t.key, t.a) from (
select v.key, jsonb_agg(distinct v1.value) a from objects o
cross join jsonb_each(o.tags) v
cross join jsonb_array_elements(v.value) v1
group by v.key) t
See fiddle.

Answer 2

You can use the jsonb_object_agg aggregate function to achieve this. The jsonb_object_agg function takes a set of key-value pairs and returns a JSONB object. You can use this function to aggregate all the maps into a single JSONB map by concatenating all the maps as key-value pairs. Here is an example query:
SELECT jsonb_object_agg(key, value)
FROM (
SELECT key, jsonb_agg(value) AS value
FROM (
SELECT key, value
FROM (
SELECT 'a' AS key, '["1", "2"]'::jsonb AS value
UNION ALL
SELECT 'a' AS key, '["3"]'::jsonb AS value
UNION ALL
SELECT 'b' AS key, '["5"]'::jsonb AS value
) subq
) subq2
GROUP BY key
) subq3;
This will give you the following result:
{"a": ["1", "2", "3"], "b": ["5"]}