Grails/Hibernate Batch Insert

I am using STS + Grails 1.3.7开发者_如何学运维 and doing the batch insertion for thousands instances of a domain class.

It is very slow because Hibernate simply batch all the SQL statements into one JDBC call instead of combining the statements into one.

How can I make them into one large statement?

What you can do is to flush the hibernate session each 20 insert like this :

int cpt = 0
mycollection.each{
 cpt ++
 if(cpt > 20){
  mycollection.save(flush:true)
 }
 else{
  mycollection.save()
 }
}

The flushing of hbernate session executes the SQL statement each 20 inserts. This is the easiest method but you can find more interessant way to do it in Tomas lin blog. He is explaining exactly what you want to do : http://fbflex.wordpress.com/2010/06/11/writing-batch-import-scripts-with-grails-gsql-and-gpars/

Using the withTransaction() method on the domain classes makes the inserts much faster for batch scripts. You can build up all of the domain objects in one collection, then insert them in one block.

For example:

Player.withTransaction{
    for (p in players) {
        p.save()
    }
}

You can see this line in Hibernate doc:

Hibernate disables insert batching at the JDBC level transparently if you use an identity identifier generator.

When I changed the type of generator, it worked.