I am wondering if there is any possible way to stream things into and out of the database using hibernate? My situation is I have potentially large blob objects, that are large enough that I cannot afford the memory to hold onto two copies in memory, thus i would like to stream to/from the database, and only ever hold 1 instance in memory. This can be accomplished using PreparedStatement/ResultSet.. is it doable with hibernate and mysql?

Try query.scroll() with evicting objects

see the sample here...
http://www.hibernate.org/hib_docs/v3/re ... tch-update

Usual way to handle this stuff is to map the property as type java.sql.Blob (Hibernate type "blob"), and let your JDBC driver take care of the streaming.

The problem I'm running into right now is I have it set to a clob (soon to change), and a string on the pojo. When I profile the app with a ~1meg clob I'm getting 6meg in char[] allocations from PreparedStatement.setString (coming down from dehydrate), and then ~1meg in byte[] allocations from PreparedStatement.fillSendPacket... so I need to get that down as much as possible, any ideas? I'm using MySQL 4.1.x for reference.