PostgreSQL does not support sub-transactions, but the
SAVEPOINT feature can effectively answer your need. Quoting from the documentation for Advanced access layer to PG via promises by Vitaly Tomilov on GitHub:
PostgreSQL doesn't have proper support for nested transactions, it only supports partial rollbacks via savepoints inside transactions. The difference between the two techniques is huge, as explained further.
Proper support for nested transactions means that the result of a successful sub-transaction isn't rolled back when its parent transaction is rolled back. But with PostgreSQL save-points, if you roll-back the top-level transaction, the result of all inner save-points is also rolled back.
Savepoints can be used for partial rollbacks to an earlier point inside an active transaction. For example, to establish a savepoint and later undo the effects of all commands executed after it was established:
INSERT INTO table1 VALUES (1);
INSERT INTO table1 VALUES (2);
ROLLBACK TO SAVEPOINT my_savepoint;
INSERT INTO table1 VALUES (3);
The above transaction will insert the values 1 and 3, but not 2. See the
SAVEPOINT documentation for more information.