JSONB select result in one row - postgresql

Question

I need your help on this. I'm trying to achieve a query for a jsonb column information I have in a table. My jsonb is an array of objects and in every object I have two key/value pairs. In this case, I have a key/value to exclude and only get the another one key without it value. So, I figure it out how to do it like:
jsonb : '[{"track":"value","location":"value"},{"extra":"value","location":"value"},...{"another":"value","location":"value"}]'
SELECT id, jsonb_object_keys((item::jsonb - 'location')::jsonb)
FROM mytable, jsonb_array_elements(theJsonB) with ordinality arr(item,position)
WHERE offer = '0001'
This query, get me the result like
id | jsonb_object_keys
-----------------------
1 | track
1 | extra
... |
1 | another
But I need to get the result in only one row for each id like
id | column1 | column2 | ... | column+
------------------------
1 | track | extra | ... | another
2 | track | extra | ... | another
3 | track | extra | ... | another
4 | track | extra | ... | another
How I could solve this? Thanks in advance, I'm a pretty newbie in SQL but I'm working hard ;-)

Answer 1

If you know the list of the resulting columns only at the runtime then you need some piece of dynamic sql code.
Here is a full dynamic solution which relies on the creation of a user-defined composite type and on the standard functions jsonb_populate_record and jsonb_object_agg :
First you dynamically create the list of keys as a new composite type :
CREATE OR REPLACE PROCEDURE key_list (NewJsonB jsonb) LANGUAGE plpgsql AS
$$
DECLARE key_list text ;
BEGIN
IF NewJsonB IS NULL
THEN
SELECT string_agg(DISTINCT k.object->>'key' || ' text', ',')
INTO key_list
FROM mytable
CROSS JOIN LATERAL jsonb_path_query(theJsonB, '$[*].keyvalue()[*] ? (#.key != "location")') AS k(object) ;
ELSE SELECT string_agg(DISTINCT k.key :: text || ' text', ',')
FROM (SELECT jsonb_object_keys(to_jsonb(a.*)) AS key FROM (SELECT(null :: key_list).*) AS a
UNION ALL
SELECT jsonb_path_query(NewJsonB, '$[*].keyvalue()[*] ? (#.key != "location")')->>'key'
) AS k
INTO key_list ;
END IF ;
EXECUTE 'DROP TYPE IF EXISTS key_list ' ;
EXECUTE 'CREATE TYPE key_list AS (' || COALESCE(key_list, '') || ')' ;
END ;
$$ ;
CALL key_list(NULL) ;
Then you call the procedure key_list() by trigger when the list of keys is supposed to be modified :
CREATE OR REPLACE FUNCTION mytable_insert_update()
RETURNS trigger LANGUAGE plpgsql VOLATILE AS
$$
BEGIN
IF NOT EXISTS (SELECT jsonb_object_keys(to_jsonb(a.*)) FROM (SELECT(null :: key_list).*) AS a)
THEN CALL key_list(NULL) ;
ELSIF EXISTS ( SELECT jsonb_path_query(NEW.theJsonB, '$[*].keyvalue()[*] ? (#.key != "location")')->>'key'
EXCEPT ALL
SELECT jsonb_object_keys(to_jsonb(a.*)) FROM (SELECT(null :: key_list).*) AS a
)
THEN CALL key_list(NEW.theJsonB) ;
END IF ;
RETURN NEW ;
END ;
$$ ;
CREATE OR REPLACE TRIGGER mytable_insert_update AFTER INSERT OR UPDATE OF theJsonB ON mytable
FOR EACH ROW EXECUTE FUNCTION mytable_insert_update() ;
CREATE OR REPLACE FUNCTION mytable_delete()
RETURNS trigger LANGUAGE plpgsql VOLATILE AS
$$
BEGIN
CALL key_list (NULL) ;
RETURN OLD ;
END ;
$$ ;
CREATE OR REPLACE TRIGGER mytable_delete AFTER DELETE ON mytable
FOR EACH ROW EXECUTE FUNCTION mytable_delete() ;
Finally, you should get the expected result with the following query :
SELECT (jsonb_populate_record(NULL :: key_list, jsonb_object_agg(lower(c.object->>'key'), c.object->'key'))).*
FROM mytable AS t
CROSS JOIN LATERAL jsonb_path_query(t.theJsonB, '$[*].keyvalue()[*] ? (#.key != "location")') AS c(object)
GROUP BY t
full test result in dbfiddle.