Problem with JSONB functions retrieving arrays

Question

In a table called temporay_data with a data field called temporary_data too, filled with this JSON structure

{
 "FormPayment": {
        "student": [
            {
                "fullname": "name student1 ",
                "rate": 210,
                "meal": 7,
                "mealValue": 175,
                "finalValue": 385,
                "role": "student",
                "willPay": true
            },
            {
                "fullname": "name student2",
                "rate": 210,
                "meal": 7,
                "mealValue": 175,
                "finalValue": 385,
                "role": "student",
                "willPay": true
            },
            {
                "fullname": "name student3",
                "rate": 210,
                "meal": 7,
                "mealValue": 175,
                "finalValue": 385,
                "role": "student",
                "willPay": true
            }
        ],
        "advisor": [
            {
                "fullname": "name advisor",
                "rate": 210,
                "meal": 7,
                "mealValue": 175,
                "finalValue": 385,
                "role": "advisor",
                "isParticipant": "yes",
                "willPay": true
            }
        ],
        "coadvisors": [
            {
                "fullname": "name coadvisors 1",
                "rate": 210,
                "meal": 7,
                "mealValue": 175,
                "finalValue": 385,
                "role": "coadvisor",
                "isParticipant": "yes",
                "willPay": true
            },
            {
                "fullname": "name coadvisors 2",
                "rate": 210,
                "meal": 7,
                "mealValue": 175,
                "finalValue": 385,
                "role": "coadvisor",
                "isParticipant": "no",
                "willPay": false
            }
        ]
    }
}

I need to select all fullnames, I know thats is an array in json. I tried the code above (and various others)

SELECT elements->>'fullname' as fullname
FROM (
    SELECT jsonb_array_elements(temporary_data->'FormPayment'->'student') as elements
    FROM temporary_data
) subquery;


and return this error 

ERROR:  function jsonb_array_elements(json) does not exist
LINE 31:     SELECT jsonb_array_elements(temporary_data->'FormPayment...
                    ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
SQL state: 42883
Character: 687

Jsonb is istalled and functions jsonb_array_elements and jsonb_array_elements_text are installed.

I've tried all above

SELECT elements->>'fullname' as fullname
FROM (
    SELECT jsonb_array_elements(temporary_data->'FormPayment'->'student') as elements
    FROM temporary_data

    UNION

    SELECT jsonb_array_elements(temporary_data->'FormPayment'->'coadvisors') as elements
    FROM temporary_data
) subquery;
</code>
<code>
SELECT jsonb_array_elements(temporary_data->'FormPayment'->'student'->'{fullname}'::jsonb[]) as elements
FROM temporary_data;
</code>
<code>
SELECT jsonb_array_elements(temporary_data->'FormPayment'->'student')->>'fullname' as fullname
FROM temporary_data;

Answer 1

ERROR: function jsonb_array_elements(json) does not exist

The solution is trivial:
Either use the function json_array_elements() or pass in jsonb (instead of json).

Answer 2

With a convoluted JSON structure as this, I would use a JSONPATH query:

SELECT *
FROM jsonb_path_query(
        CAST (/* your JSON */ AS jsonb),
        '$.**.fullname'
     );

Answer 3

Tanks Erwin Brandstetter. I solved with your help and now a I post the solution.

 SELECT subquery.project_id,
    subquery.elements ->> 'fullname'::text AS fullname,
    subquery.elements ->> 'meal'::text AS meal,
    subquery.elements ->> 'role'::text AS tipo
   FROM ( SELECT json_array_elements((td.temporary_data -> 'FormPayment'::text) -> 'student'::text) AS elements,
            p.project_id
           FROM temporary_data td
             JOIN projects p ON td.id = p.temporary_data_id
          WHERE p.mostratec_id = 6 AND (p.status_id = ANY (ARRAY[4, 5]))) subquery