SAVEPOINT — define a new savepoint within the current transaction
SAVEPOINT establishes a new savepoint within
the current transaction.
A savepoint is a special mark inside a transaction that allows all commands that are executed after it was established to be rolled back, restoring the transaction state to what it was at the time of the savepoint.
The name to give to the new savepoint.
Savepoints can only be established when inside a transaction block. There can be multiple savepoints defined within a transaction.
To establish a savepoint and later undo the effects of all commands executed after it was established:
BEGIN; INSERT INTO table1 VALUES (1); SAVEPOINT my_savepoint; INSERT INTO table1 VALUES (2); ROLLBACK TO SAVEPOINT my_savepoint; INSERT INTO table1 VALUES (3); COMMIT;
The above transaction will insert the values 1 and 3, but not 2.
To establish and later destroy 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.
SQL requires a savepoint to be destroyed automatically when another
savepoint with the same name is established. In
PostgreSQL, the old savepoint is kept, though only the more
recent one will be used when rolling back or releasing. (Releasing the
newer savepoint with
RELEASE SAVEPOINT will cause the older one
to again become accessible to
ROLLBACK TO SAVEPOINT and
RELEASE SAVEPOINT.) Otherwise,
fully SQL conforming.