fetch
目的 Purpose
Configures the fetching behavior of an association.
使用例 Examples
class Author { static hasMany = [books: Book]
static mapping = {
books fetch: 'join'
}
}
詳細 Description
Usage:
使用方法: association_name(fetch:string)Usage:
association_name(fetch:string)引数:
Arguments:
fetchStrategy- The fetching strategy to use. Eitherjoinorselect.
By default GORM assumes fetching of associations is done using a SELECT when the association is accessed. If you prefer that the association be fetched eagerly at the same time then you can override the behavior:
class Author { static hasMany = [books: Book]
static mapping = {
books fetch: 'join'
}
}
Here the books association will be fetched using a join at the same time the author is retrieved, for example:
def author = Author.get(1) // the books collection is pre-initialized - no risk of lazy loading exceptions
Note that excessive use of joins can be a performance bottleneck. See the section on Eager vs Lazing Fetching in the user guide.