How to change the default isolation level of a transaction in a stored procedure in PostgreSQL PL/pgSQL? I am interested in controlling the isolation level of a transaction inside a PostgreSQL procedure but haven't found any information on how to do it. The documentation on Transaction Management within Chapter 42. PL/pgSQL — SQL Procedural Language only states that:

A new transaction starts out with default transaction characteristics such as transaction isolation level.

Can we change the default isolation level? Can you provide example code?
That should be simple:
ALTER PROCEDURE myproc
   SET default_transaction_isolation = 'repeatable read';

The downside to that is that because of the limitations of transaction management inside procedures, you can no longer COMMIT or ROLLBACK inside such a procedure.
If you need that, you could start the procedure body like this:
COMMIT;  -- otherwise you get a silly error
SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;

Transaction management inside procedures is pretty limited at the moment.