Hibernate - HQL pagination

Question

This is a problem similar to: HQL - row identifier for pagination

I\'m trying to implement pagination using HQL. I have a PostgreSQL database.

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Answer 1

Since you do not filter the result set with respect to some attributes of command entity, you could also avoid the SQL join and configure lazy fetching for message's commands. Without join, Hibernate will employ the database paging cabilities.

However, you have to care about the N+1 seletcs issue, i.e. avoiding a single select for each lazily fetched commands attribute. You can avoid this by setting the batch-size property in your hibernate mapping or globally the hibernate.default_batch_fetch_size property in your hibernate settings.

For instance: If you have fetched 100 message objects within a Hibernate session and set a batch-size of 10, Hibernate will fetch 10 command associations of 10 different message objects when you first call getCommands() of a message object. The number of queries is reduced to 10 plus the original message-fetching one.

Have a look here: http://java.dzone.com/articles/hibernate-tuning-queries-using?page=0,1 The author compares the different fetch strategies for a simple example