How to make a selection, update records for it and return a cursor with them?

Question

PostgreSQL

Good day to all, Postgres database I'm
new to writing functions.
I want to take N records from the database for processing in Java. This action may be attempted by several different applications. To prevent a situation where several applications have taken a new record to work and process it together, there is a status column. 0-new record, 1-in process, 2-done.
The essence of the question is - I want to get N records with a select, set their status to 1 and pass the cursor on them to the Java application. Thus, other applications will not be able to take these records. For the life of me, I can't do it in a function in Postgres, apparently Java of the brain. Can you give an approximate sequence of actions to get the desired result?

Answer 1

There is no need to reinvent the wheel with another queue. It won't work under load. Take pgq.
Well, if you still want to collect this rake:

update tablename set status = 1
where status = 0 and id in (
select id from tablename where ..... order by ... limit ... for update
)
returning ...