search by parent entity

rygel · **Joined:** Tue May 12, 2009 5:53 am **Posts:** 1

Hi! i try to use hibernate search and have some troubles. Help me please.
I 've got two entities: File and Category. The File can belong to several categories. Categories have some hierarchy.

Code:

@Entity
@Indexed
@Table(name = "file")
public class File implements BusinessEntity {

........
@ManyToMany (cascade = {CascadeType.PERSIST})
    @JoinTable(
            name = "file_category",
            joinColumns = {@JoinColumn(name = "file_id", nullable = false)},
            inverseJoinColumns = {@JoinColumn(name = "category_id", nullable = false)}
    )
    @LazyCollection(LazyCollectionOption.FALSE)
    @Cascade(
            org.hibernate.annotations.CascadeType.PERSIST
    )
    @IndexedEmbedded
    public List<Category> getCategories() {
        return categories;
    }

Code:

@Entity
@Table(name = "cpa_category")
@Indexed
public class Category implements BusinessEntity {
...............
@OneToMany (mappedBy = "parent", cascade = CascadeType.ALL)
    @LazyCollection(LazyCollectionOption.FALSE)
    public List<Category> getChildrens() {
        return childrens;
    }

Now i can search by concrete categories id, but i want search by parent category id.
For example;
- Programming
- Java
- Swing
- AWT
And file in AWT category. So by AWT id i can find the file, but what if i need to search by Programming id and find all files of all children categories?
Thank you!

sanne.grinovero · **Posted:** Thu May 14, 2009 1:45 am

Hi,
basically you have created a link from each file to a set of categories, containing the parents of all directly related categories. This link has to be fully traversed to identify all entities; you have the option to do this traversal at indexing time or at query time. IMHO is indexing time better for your application, but will make indexing slower.

The solution is to use @IndexedEmbedded on the getParent() in the Category, so that you will store the category ids and the parent ids in the index of File; set the prefix attribute to "" to make sure that the fields will have the same name (categories.id), indipendently of the depth in the tree.

Then you can filter on the selected category and it should be very efficient at query time. Using a filter with a category parameter will also enable caching.