Postgres find unique values ​in json - sql

Question

I am using Postgresql and have a table, with id, sender::jsonb and date, as follows:
id | sender | last login date
----+-----------------------------------------------------------------------------------+----------------------------------
1 | {"firstName": "Ivan", "lastName": "Ivanov", "middleName": "Ivanovich", } | 2021-04-10 14:49:36.234504 +00:00
2 | {"firstName": "Ivan", "lastName": "Ivanov", "middleName": "Ivanovich", } | 2021-04-09 14:49:36.234504 +00:00
3 | {"firstName": "Ivan", "lastName": "Ivanov", "middleName": "Ivanovich", } | 2021-04-11 14:49:36.234504 +00:00
4 | {"firstName": "Nickolai","lastName": "Nickov", "middleName": "Nikovich", } | 2021-04-30 14:49:36.234504 +00:00
5 | {"firstName": "Nickolai","lastName": "Nickov", "middleName": "Nikovich", } | 2021-04-29 14:49:36.234504 +00:00
6 | {"firstName": "Vladimir","lastName": "Vladimirovich","middleName": "Putout", } | 2021-04-15 14:49:36.234504 +00:00
7 | {"firstName": "Petr", "lastName": "Petrov", "middleName": "Petrovich", } | 2021-04-10 14:49:36.234504 +00:00
8 | {"firstName": "Ivan", "lastName": "Ivanov", "middleName": "Ivanovich", } | 2021-04-01 14:49:36.234504 +00:00
9 | {"firstName": "Ignat", "lastName": "Ignatov", "middleName": "Ignatovich", }| 2021-04-06 14:49:36.234504 +00:00
10| {"firstName": "Vladimir","lastName": "Vladimirovich","middleName": "Putout", } | 2021-04-17 14:49:36.234504 +00:00
11| {"firstName": "Ivan", "lastName": "Ivanov", "middleName": "Ivanovich", } | 2021-04-12 14:49:36.234504 +00:00
p.s.There may be other information in the "sender" column, but the search for uniqueness is only necessary by "firstName", "lastName", "midddleName"
It is necessary to return a result consisting of unique names and with the latest date. In particular, I want to get the result:
id | sender | last login date
----+-----------------------------------------------------------------------------------+----------------------------------
4 | {"firstName": "Nickolai","lastName": "Nickov", "middleName": "Nikovich", } | 2021-04-30 14:49:36.234504 +00:00
10| {"firstName": "Vladimir","lastName": "Vladimirovich","middleName": "Putout", } | 2021-04-17 14:49:36.234504 +00:00
11| {"firstName": "Ivan", "lastName": "Ivanov", "middleName": "Ivanovich", } | 2021-04-12 14:49:36.234504 +00:00
7 | {"firstName": "Petr", "lastName": "Petrov", "middleName": "Petrovich", } | 2021-04-10 14:49:36.234504 +00:00
9 | {"firstName": "Ignat", "lastName": "Ignatov", "middleName": "Ignatovich", }| 2021-04-06 14:49:36.234504 +00:00
Everything is very complicated by the fact that json is used. I had thoughts to do - "name" concatenation and perform group by and sorting, but unfortunately it does not work.

Answer 1

You can use distinct on() to do this:
select distinct on (firstname, lastname) id, sender, last_login_date
from (
select id, sender, last_login_date,
sender ->> 'firstName' as firstname,
sender ->> 'lastName' as lastname
from the_table
) t
order by firstname, lastname, last_login_date desc

Answer 2

you can do it using window function :
select * from
(
select * ,rank() over (partition by sender->> 'firstName',sender->> 'lastName' order by last_login_date desc) rn
from yourtable
) t
where rn = 1
order by last_login_date desc
db<>fiddle here