Postgres, update statement from jsonb array with sorting - postgresql

Question

I have a jsonb column in my table - it contains array of json objects
one of fields in these objects is a date.
Now i added new column in my table of type timestamp.
And now i need statement which hepls me to update new column with most recent date value from jsonb array column af a same record.
Following statement works great on selecting most recent date from jsonb array column of certain record:
select history.date
from document,
jsonb_to_recordset(document.history) as history(date date)
where document.id = 'd093d6b0-702f-11eb-9439-0242ac130002'
order by history.date desc
limit 1;
On update i have tried following:
update document
set status_recent_change_date = subquery.history.date
from (
select id, history.date
from document,
jsonb_to_recordset(document.history) as history(date date)
) as subquery
where document.id = subquery.id
order by history.date desc
limit 1;
Last statement does not working.

Answer 1

demo:db<>fiddle
UPDATE document d
SET status_recent_change_date = s.date
FROM (
SELECT DISTINCT ON (id)
*
FROM document,
jsonb_to_recordset(document.history) AS history(date date)
ORDER BY id, history.date DESC
) s
WHERE d.id = s.id;
Using LIMIT would not work because you limit the entire output of your SELECT statement. But you want to limit the output of each document.id. This can be done using DISTINCT ON (id).
This result can be used to update each record using their id values.

Answer 2

You most likely don't need to use LIMIT command.
It is enough to do the sorting inside SUBQUERY:
UPDATE document SET status_recent_change_date = subquery.hdate
FROM (
SELECT id, history.date AS hdate
FROM document, jsonb_to_recordset(document.history) AS history(date date)
ORDER BY history.date DESC
) AS subquery
WHERE document.id = subquery.id