How do I modify a single property value inside the PostgreSQL JSONB datatype?

Question

How do I modify a single field inside the PostgreSQL JSONB datatype?

Let's say I have a table called animal like this:

id       info
------------------------------------------------------------
49493   {"habit1":"fly","habit2":"dive","location":"SONOMA NARITE"}

I'd like to simply change value(say, to upper case or lower case the text) of the location property. so the result, after UPDATE is

    id       info
------------------------------------------------------------
49493   {"habit1":"fly","habit2":"dive","location":"sonoma narite"}

I tried this below and it does not work

update animal set info=jsonb_set(info, '{location}', LOWER(info->>'location'), true) where id='49493';
----------------------------------
ERROR:  function jsonb_set(jsonb, unknown, text, boolean) does not exist
LINE 7: update animal set info=jsonb_set(info, '{con...
                                           ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
********** Error **********

ERROR: function jsonb_set(jsonb, unknown, text, boolean) does not exist

if I simply know what the updated value would be then I can use just use this:

update animal set info=jsonb_set(info, '{location}', '"sonoma narite"', true) where id='49493';

However, if the text value is unknown and we just want to do some simply operation such as append, prepend, upper/lower case, I can't simply find an answer to it.

I was surprised by the fact that jsonb set function does not offer such a trivial operation that only try to update the case of a text property inside a jsonb.

Can someone help?

Answer 1

The third argument of jsonb_set() should be of jsonb type. The problem is in casting a text string to jsonb string, you need a string in double quotes. You can use concat() or format():

update animal
set info = 
    jsonb_set(info, '{location}', concat('"', lower(info->>'location'), '"')::jsonb, true) 
--  jsonb_set(info, '{location}', format('"%s"', lower(info->>'location'))::jsonb, true) 
where id='49493'
returning *;

  id   |                               info                               
-------+------------------------------------------------------------------
 49493 | {"habit1": "fly", "habit2": "dive", "location": "sonoma narite"}
(1 row)

---

In Postgres 9.4 you should unnest the json column using jsonb_each_text(), aggregate keys and values modifying the proper value on the fly, and finally build a json object:

update animal a
set info = u.info
from (
    select id, json_object(
        array_agg(key), 
        array_agg(
            case key when 'location' then lower(value)
            else value end))::jsonb as info
    from animal,
    lateral jsonb_each_text(info) 
    group by 1
    ) u
where u.id = a.id
and a.id = 49493;

If you can create functions this solution might be more pleasant:

create or replace function update_info(info jsonb)
returns jsonb language sql as $$
    select json_object(
        array_agg(key), 
        array_agg(
            case key when 'location' then lower(value)
            else value end))::jsonb
    from jsonb_each_text(info)
$$

update animal
set info = update_info(info)
where id = 49493;