Nils,
Have you tried groupBy by more than one key(groupBy="key1, key2)?
If you see my previous post. During the test, I turned ibatis and sql
log to debug level. I saw the queried data in result set. Somehow,
groupBy cannot pick it up and always set the list to null.
thx,
Tony
Nils Winkler wrote on 2/3/2006, 2:51 AM:
> I have something like this working. Here's roughly what I'm doing:
>
> - Create a single select using joins across the tables.
> - Make sure that each of the selected columns has a unique alias, e.g.
> "category_name"
> - Test the query in a SQL tool to make sure you get what you want. You
> should have multiple rows for each user.
> - Create result maps for User, Group and Category.
> - Link the Group and Category result maps into the User result map:
> <result property="groups" column="user_id" resultMap="userGroups" />
> - Each of the result maps should have the groupBy attribute set to its
> own primary key attribute:
>
> class User { private int userId;}
> class Group { private int groupId;}
> class Category {private int catId;}
>
> <resultMap id="user" class="User" groupBy="userId">...</resultMap>
> <resultMap id="group" class="Group" groupBy="groupId">...</resultMap>
> <resultMap id="category" class="Category"
> groupBy="catId">...</resultMap>
>
> - For testing, start with only one relationship, e.g. Group, leave out
> Category. Once this works, add Category again.
>
> The example in the Wiki is too simple IMHO, we should try to add a more
> complex one...
>
> Nils
>
> On Thu, 02 Feb 2006 21:10:50 +1100, "Zoran Avtarovski"
> <[EMAIL PROTECTED]> said:
> > I've been trying to get a n+1 example to work without much luck and I
> > think
> > that I may have misunderstood the wiki article. I have intentionally
> kept
> > the example simple so I can fully understand the concepts and then
> apply
> > it
> > to the real world app which uses the same principles.
> >
> > I have three object tables
> > User, which has {user_id, name, type} columns
> > Group, which has {group_id, name, description} columns
> > Category, which has {cat_id, name, description} columns
> >
> > I also have two relationship tables
> > UserGroup, which has {user_id, group_id} columns
> > UserCat, which has {user_id, group_id} columns
> >
> > Each User can have multiple Groups and Categories. This is represented
> > through a User POJO which includes two Collection properties {groups,
> > categories} with appropriate setters and getters.
> >
> > I currently use multiple SQL calls to populate the n+1 properties, I
> use
> > a
> > <result property="groups" column="user_id" select="getUserGroups"
> /> and
> > the same for categories. You get the Idea. Ideally, I'd really like to
> > use a
> > single SQL query to improve system performance.
> >
> > Can I resolve multiple n+1 relationships in a single call and if so
> how.
> > I'd
> > appreciate any help. I'm sure that once I get my head around the
> concept
> > of
> > n+1 selects it will be easy.
> >
> > Zoran
> >
> >
> --
> ==================================
> [EMAIL PROTECTED]
>
