SAVEPOINTidentifierROLLBACK TO SAVEPOINTidentifier
Starting from MySQL 4.0.14 and 4.1.1, InnoDB
supports the SQL statements SAVEPOINT and
ROLLBACK TO SAVEPOINT.
The SAVEPOINT statement sets a named
transaction save point with a name of
identifier. If the current transaction
has a save point with the same name, the old save point is deleted
and a new one is set.
The ROLLBACK TO SAVEPOINT statement rolls back
a transaction to the named save point. Modifications that the
current transaction made to rows after the save point was set are
undone in the rollback, but InnoDB does
not release the row locks that were stored in
memory after the save point. (Note that for a new inserted row,
the lock information is carried by the transaction ID stored in
the row; the lock is not separately stored in memory. In this
case, the row lock is released in the undo.) Savepoints that were
set at a later time than the named save point are deleted.
If the ROLLBACK TO SAVEPOINT statement returns
the following error, it means that no savepoint with the specified
name exists:
ERROR 1181: Got error 153 during ROLLBACK
All save points of the current transaction are deleted if you
execute a COMMIT, or a
ROLLBACK that does not name a save point.

User Comments
Savepoints apply only to an already started transaction. They do not start a transaction themselves. So if you're getting 'SAVEPOINT foobar does not exist' errors, make sure you've actually started a transaction _and_ made the savepoint.
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