RELEASE SAVEPOINT — release a previously defined savepoint
RELEASE [ SAVEPOINT ] savepoint_name
   RELEASE SAVEPOINT releases the named savepoint and
   all active savepoints that were created after the named savepoint,
   and frees their resources.  All changes made since the creation of
   the savepoint that didn't already get rolled back are merged into
   the transaction or savepoint that was active when the named savepoint
   was created.  Changes made after RELEASE SAVEPOINT
   will also be part of this active transaction or savepoint.
  
savepoint_nameThe name of the savepoint to release.
Specifying a savepoint name that was not previously defined is an error.
It is not possible to release a savepoint when the transaction is in an aborted state; to do that, use ROLLBACK TO SAVEPOINT.
If multiple savepoints have the same name, only the most recently defined unreleased one is released. Repeated commands will release progressively older savepoints.
To establish and later release a savepoint:
BEGIN;
    INSERT INTO table1 VALUES (3);
    SAVEPOINT my_savepoint;
    INSERT INTO table1 VALUES (4);
    RELEASE SAVEPOINT my_savepoint;
COMMIT;
The above transaction will insert both 3 and 4.
A more complex example with multiple nested subtransactions:
BEGIN;
    INSERT INTO table1 VALUES (1);
    SAVEPOINT sp1;
    INSERT INTO table1 VALUES (2);
    SAVEPOINT sp2;
    INSERT INTO table1 VALUES (3);
    RELEASE SAVEPOINT sp2;
    INSERT INTO table1 VALUES (4))); -- generates an error
   In this example, the application requests the release of the savepoint
   sp2, which inserted 3.  This changes the insert's
   transaction context to sp1.  When the statement
   attempting to insert value 4 generates an error, the insertion of 2 and
   4 are lost because they are in the same, now-rolled back savepoint,
   and value 3 is in the same transaction context.  The application can
   now only choose one of these two commands, since all other commands
   will be ignored:
ROLLBACK; ROLLBACK TO SAVEPOINT sp1;
   Choosing ROLLBACK will abort everything, including
   value 1, whereas ROLLBACK TO SAVEPOINT sp1 will retain
   value 1 and allow the transaction to continue.
  
   This command conforms to the SQL standard.  The standard
   specifies that the key word SAVEPOINT is
   mandatory, but PostgreSQL allows it to
   be omitted.