Does use of the native identifier generation cause a commit to the database even when the connection's autocommit is set to false? When doing a save on an entity inside a transaction, it gets saved to the database even when I invoke rollback instead of commit. Hibernate does an insert to get the database-generated identifier, but that insert is not undone when I call rollback after the save.

Hibernate version: 3.0

Mapping documents:
<hibernate-mapping>
<class name="uexp.model.Venue" table="venues">
<id name="venueKey" column="venue_id" unsaved-value="0">
<generator class="native"/>
</id>
<property name="venueId" column="uid" type="uexp.dao.impl.hibernate.UidUserType" not-null="true" unique="true" access="field"/>
<property name="name" column="name" not-null="true"/>
<property name="address" column="address"/>
<property name="phone" column="phone"/>
<many-to-one name="parent" column="parent" class="uexp.model.Venue" access="field"/>
</hibernate-mapping>

Code between sessionFactory.openSession() and session.close():
tx = session.beginTransaction();
session.save(venue);
tx.rollback();

Full stack trace of any exception that occurs:

Name and version of the database you are using: MySQL 4.0.20a

The generated SQL (show_sql=true): insert into venues (uid, name, address, phone, parent) values (?, ?, ?, ?, ?)

Debug level Hibernate log excerpt:
2005-07-05 23:18:07,696 -DEBUG- [in] {JDBCTransaction} begin
2005-07-05 23:18:07,696 -DEBUG- [in] {JDBCTransaction} current autocommit status: false
2005-07-05 23:18:07,696 -DEBUG- [in] {DefaultSaveOrUpdateEventListener} saving transient instance
2005-07-05 23:18:07,696 -DEBUG- [in] {AbstractSaveEventListener} generated identifier: , using strategy: org.hibernate.id.IdentityGenerator
2005-07-05 23:18:07,696 -DEBUG- [in] {AbstractSaveEventListener} saving [uexp.model.Venue#<null>]
2005-07-05 23:18:07,696 -DEBUG- [in] {AbstractSaveEventListener} executing insertions
2005-07-05 23:18:07,696 -DEBUG- [in] {BasicEntityPersister} Inserting entity: uexp.model.Venue (native id)
2005-07-05 23:18:07,696 -DEBUG- [in] {AbstractBatcher} about to open PreparedStatement (open PreparedStatements: 0, globally: 0)
2005-07-05 23:18:07,696 -DEBUG- [in] {SQL} insert into venues (uid, name, address, phone, parent) values (?, ?, ?, ?, ?)
2005-07-05 23:18:07,696 -DEBUG- [in] {AbstractBatcher} preparing statement
2005-07-05 23:18:07,696 -DEBUG- [in] {BasicEntityPersister} Dehydrating entity: [uexp.model.Venue#<null>]
2005-07-05 23:18:07,706 -DEBUG- [in] {IdentifierGeneratorFactory} Natively generated identity: 1022
2005-07-05 23:18:07,706 -DEBUG- [in] {AbstractBatcher} about to close PreparedStatement (open PreparedStatements: 1, globally: 1)
2005-07-05 23:18:07,706 -DEBUG- [in] {AbstractBatcher} closing statement
2005-07-05 23:18:07,706 -DEBUG- [in] {JDBCTransaction} rollback
2005-07-05 23:18:07,706 -DEBUG- [in] {JDBCContext} before transaction completion
2005-07-05 23:18:07,706 -DEBUG- [in] {SessionImpl} before transaction completion
2005-07-05 23:18:07,706 -DEBUG- [in] {JDBCTransaction} rolled back JDBC Connection
2005-07-05 23:18:07,706 -DEBUG- [in] {JDBCContext} after transaction completion
2005-07-05 23:18:07,706 -DEBUG- [in] {SessionImpl} after transaction completion
2005-07-05 23:18:08,146 -DEBUG- [in] {SessionImpl} closing session
2005-07-05 23:18:08,146 -DEBUG- [in] {ConnectionManager} closing JDBC connection [ (open PreparedStatements: 0, globally: 0) (open ResultSets: 0, globally: 0)]
2005-07-05 23:18:08,146 -DEBUG- [in] {JDBCContext} after transaction completion
2005-07-05 23:18:08,146 -DEBUG- [in] {SessionImpl} after transaction completion
2005-07-05 23:18:08,146 -INFO - [in] {VenueManager} Saved venue with uid = 9e7d8004eacb47d0

There's nothing committed to the database as you can see from the log. Since you're using sequence/auto-increment id, the database always increments the counter regardless of transaction to ensure all transactions will get a unique id. Check the mysql doc for auto-increment id.

fyi, hibernate obtains the nextid by invoking last_insert_id (http://www.mysqlfreaks.com/statements/90.php)

I solved the problem.

First, Hibernate does send a full insert command to the database rather than just invoking last_insert_id. That is the insert that shows up in the Hibernate log file.

The problem is not with Hibernate. Looking at the MySQL logs (not shown here), Hibernate is behaving as a good citizen. The problem lies in the way I created the tables in MySQL.

In order to get expected transactional behavior when using the InnoDB version of MySQL, you need to append an extra tag at the end of the table create command:

CREATE TABLE User (username VARCHAR(30)) TYPE=InnoDB;

The TYPE attribute makes all the difference.