http://opensource.atlassian.com/projects/hibernate/browse/HHH-1 /max > I thought his question was a little too technical for the general list, so I > thought I¹d ask it here. Is there a technical reason why Hibernate does not > or cannot support the batching of multiple (different) object insertions > within the same session? > > I have code that is semantically equivalent to: > > Session session = sessionFactory.getCurrentSession(); > for (int i = 0; i < 1000; i++) { > Foo foo = new Foo(); > session.save(foo); > > Bar bar = new Bar(); > session.save(bar); > } > session.flush(); > > If Foo or Bar is not in the equation, batching occurs as desired. However, > if both Foo and Bar are inserted during the session in alternating fashion > the result is that in the ActionQueue the 'insertion list' is interleaved > with Foo's and Bar's. This is natural enough it seems. However, when > ActionQueue.executeActions() is called the following occurs... > > 1) executeAction() iterates through the insertion list calling execute() on > each Executable in the list > 2) the Executable.execute() method calls insert() on the associated > persister, in the case a SingleTableEntityPersister. It seems to realize > that it CAN batch these inserts and so ... > 3) insert() calls the BatchingBatcher.prepareBatchStatement(sql) which is > actually a method on AbstractBatcher. This is where things go "awry"... > > The prepareBatchStatement(sql) does this thing where it compares the SQL > statement that was provided with the _last SQL that it executed_ and if they > match it re-uses the _last PreparedStatement_ which it also hung onto, > otherwise it closes the existing PreparedStatement and creates a new one -- > effectively ending the current "batch". > > In this case, because the objects are interleaved in the insertion list the > result is that the prepareBatchStatement() is called with: > > insert into foo (a, b, c) values (?, ?, ?) > insert into bar (x, y, z) values (?, ?, ?) > insert into foo (a, b, c) values (?, ?, ?) > insert into bar (x, y, z) values (?, ?, ?) > insert into foo (a, b, c) values (?, ?, ?) > insert into bar (x, y, z) values (?, ?, ?) > ... > > The result being that each subsequent statement terminates the statement > prepared before it, preventing batching from occuring. Well, it logs a > debug message saying "Executing batch size: 1" for each statement. > > So my question is this ... is there any reason not to use a Map<sql, > PreparedStatement> construct in the BatchingBatcher such that the > appropriate PreparedStatement can be located and re-used based on the > incoming SQL rather than only retaining the _last_ SQL statement which is > guaranteed to "flap" in the case of alternating (or multiple) objects? > > If there is no technical reason why this shouldn't be done or wouldn't work, > I will be happy to make the change and submit a patch. [Can you tell how > bad I need batching in this scenario?] > > Thanks, > Brett Wooldridge > The ZipTie Project > www.ziptie.org > > > _______________________________________________ > hibernate-dev mailing list > hibernate-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/hibernate-dev