JPA Performance, Don't Ignore the Database


1.    
             ,          ,                .

2.   
             ,          ,            ,        ;         ,        
           ,        .

3.JPA      
   1.                    
   2.            
   3.                      ,   ,        
4.      (N+1  )
   OneToMany ManyToMany
   With JPA many-to-one and many-to-many relationships lazy load by default, meaning they will be loaded when the entity in the relationship is accessed. Lazy loading is usually good, but if you need to access all of the "many" objects in a relationship, it will cause n+1 selects where n is the number of "many" objects.
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        [url]http://weblogs.java.net/blog/caroljmcdonald/archive/2009/08/28/jpa-performance-dont-ignore-database-0[/url]

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