CMP and Bean Cache
Hi people,
i just set up a small Bean project with JBuilder and
took a look at the SQL statements JBOSS produces while
communicating with a MySQL database.
I am using a stateless session bean looking up some
CMP entits beans and executing some getter calls on
them. The beans are connected via a bi directional relationship.
The code is like this, called 10 times in a loop:
RelnHome rH = (RelnHome) i.lookup("jb7Reln");
Reln r = rH.findByPrimaryKey(new Integer(1));
Rel1 r1 = r.getRel1();
Reln r2 = rH.findByPrimaryKey(new Integer(1));
Rel1 r21 = r2.getRel1();
Reln r3 = rH.findByPrimaryKey(new Integer(1));
Rel1 r31 = r3.getRel1();
System.out.println(":D " + r1.getName());
System.out.println("D: " + r1.getName());
The SQL statements depend on the transaction setting
for the calling session bean.
SQL for transaction set to "never":
2002-09-19 15:56:59,059 DEBUG [org.jboss.ejb.plugins.cmp.jdbc.JDBCFindByPrimaryKeyQuery.Reln.findByPrimaryKey] Executing SQL: SELECT ID_RELN FROM reln WHERE ID_RELN=?
2002-09-19 15:56:59,069 DEBUG [org.jboss.ejb.plugins.cmp.jdbc.JDBCLoadEntityCommand.Reln] Executing SQL: SELECT value, ID_REL1, ID_REL1 FROM reln WHERE (ID_RELN=?)
2002-09-19 15:56:59,069 DEBUG [org.jboss.ejb.plugins.cmp.jdbc.JDBCFindByPrimaryKeyQuery.Reln.findByPrimaryKey] Executing SQL: SELECT ID_RELN FROM reln WHERE ID_RELN=?
2002-09-19 15:56:59,079 DEBUG [org.jboss.ejb.plugins.cmp.jdbc.JDBCLoadEntityCommand.Reln] Executing SQL: SELECT value, ID_REL1, ID_REL1 FROM reln WHERE (ID_RELN=?)
2002-09-19 15:56:59,089 DEBUG [org.jboss.ejb.plugins.cmp.jdbc.JDBCFindByPrimaryKeyQuery.Reln.findByPrimaryKey] Executing SQL: SELECT ID_RELN FROM reln WHERE ID_RELN=?
2002-09-19 15:56:59,089 DEBUG [org.jboss.ejb.plugins.cmp.jdbc.JDBCLoadEntityCommand.Reln] Executing SQL: SELECT value, ID_REL1, ID_REL1 FROM reln WHERE (ID_RELN=?)
2002-09-19 15:56:59,099 DEBUG [org.jboss.ejb.plugins.cmp.jdbc.JDBCLoadEntityCommand.Rel1] Executing SQL: SELECT name FROM rel1 WHERE (ID_REL1=?)
2002-09-19 15:56:59,109 INFO [STDOUT] :D VisitY
2002-09-19 15:56:59,109 DEBUG [org.jboss.ejb.plugins.cmp.jdbc.JDBCLoadEntityCommand.Rel1] Executing SQL: SELECT name FROM rel1 WHERE (ID_REL1=?)
2002-09-19 15:56:59,109 INFO [STDOUT] D: VisitY
==> even a simple .getName() is forwarded to the database.
==> SQL statements are identical in every iteration
==> absolutely no caching, (no bean materialization?)
SQL for transaction set to "required":
2002-09-19 15:44:16,623 DEBUG [org.jboss.ejb.plugins.cmp.jdbc.JDBCFindByPrimaryKeyQuery.Reln.findByPrimaryKey] Executing SQL: SELECT ID_RELN FROM reln WHERE ID_RELN=?
2002-09-19 15:44:16,633 DEBUG [org.jboss.ejb.plugins.cmp.jdbc.JDBCLoadEntityCommand.Reln] Executing SQL: SELECT value, ID_REL1, ID_REL1 FROM reln WHERE (ID_RELN=?)
2002-09-19 15:44:16,633 DEBUG [org.jboss.ejb.plugins.cmp.jdbc.JDBCFindByPrimaryKeyQuery.Reln.findByPrimaryKey] Executing SQL: SELECT ID_RELN FROM reln WHERE ID_RELN=?
2002-09-19 15:44:16,643 DEBUG [org.jboss.ejb.plugins.cmp.jdbc.JDBCFindByPrimaryKeyQuery.Reln.findByPrimaryKey] Executing SQL: SELECT ID_RELN FROM reln WHERE ID_RELN=?
2002-09-19 15:44:16,653 DEBUG [org.jboss.ejb.plugins.cmp.jdbc.JDBCLoadEntityCommand.Rel1] Executing SQL: SELECT name FROM rel1 WHERE (ID_REL1=?)
2002-09-19 15:44:16,663 INFO [STDOUT] :D VisitY
2002-09-19 15:44:16,663 INFO [STDOUT] D: VisitY
==> caching seems to work locally
==> however, for every iteration, the SQL statements are
once again identical
==> no caching across method calls (transactions?)
Why is the caching behavour that bad and every stupid
call routed to the database? This cannot be good for
performance, its outstandingly bad!
Are there any special settings i must adjust to have
my beans cached across transactions? I could agree that
finders go the db, though i find it stupid because the
appserver could track what beans he already got and what
beans he does not, aint it?
gracefully appreciating your help!!!
Hannes
