(Quick Reference)

batchSize

Purpose

Customizes how many results are fetching during lazy loading.

Examples

class Book {
    …
    static mapping = {
        batchSize 10
    }
}

Description

Usage: batchSize(integer)

Given a lazy association where an Author has many Books, GORM will perform one query for the Author and additional queries the associated Books. This is what is known as the N+1 problem and can often be worked around by using a join query. However, joins can be expensive.

Batch fetching is an optimization of lazy loading so that if, for example, you set a batchSize of 10 and you have an Author that with 30 books, instead of 31 queries you get four (one for the Author and three batches of 10):

static mapping = {
    batchSize 10
}

You can also configure batchSize on a per association basis:

class Author {

static hasMany = [books: Book]

static mapping = { books batchSize: 10 } }