How to update JSONB array in postgres I have a table with following definition:

create table json_test (
    my_data jsonb);


Inserted to it values like this:

{"details": [
    {
        "f1": "",
        "f2": "free text"
    },
    {
        "f1": "",
        "f2": "free text"
    }
]}


Now I want to update this jsonb column(f1 to null):

{"details": [
    {
        "f1": null,
        "f2": "free text"
    },
    {
        "f1": null,
        "f2": "free text"
    }
]}


I want to change the f1 from string to null. 

How to achieve this ?
On 9.3 you will have to rewrite your jsonb value.  From 9.5 you could use jsonb_set() to simplify the task.