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http://nagoya.apache.org/jira/browse/IBATIS-27?page=comments#action_56706 ]
Clinton Begin commented on IBATIS-27:
-------------------------------------
Good news, this is already done. It will be released in 2.0.9.
Here's an example from the JPetStore DB (look for groupBy="" in resultMap and
resultMap="" in result. This is actually a double repeating group (both
category and product repeat for each item). A single repeating group mapping
will only need 2 resultMap elements. The cool thing is that it only iterates
once over the result set. It's essentially unlimited how many joins and
collections you can populate. groupBy="" can be used independently as well.
<resultMap id="categoryResult" class="testdomain.Category"
groupBy="categoryId">
<result property="categoryId" column="catid"/>
<result property="name" column="name"/>
<result property="description" column="descn"/>
<result property="productList" resultMap="productResult"/>
</resultMap>
<resultMap id="productResult" class="testdomain.Product" groupBy="productId">
<result property="productId" column="productid"/>
<result property="categoryId" column="category"/>
<result property="name" column="name"/>
<result property="description" column="descn"/>
<result property="itemList" resultMap="itemResult"/>
</resultMap>
<resultMap id="itemResult" class="testdomain.Item">
<result property="itemId" column="itemid"/>
<result property="productId" column="productid"/>
<result property="listPrice" column="listprice"/>
<result property="unitCost" column="unitcost"/>
<result property="supplierId" column="supplier"/>
<result property="status" column="status"/>
<result property="attribute1" column="attr1"/>
<result property="quantity" column="qty"/>
</resultMap>
<select id="getAllCategories" resultMap="categoryResult" >
select *
from category c, product p, item i, inventory v
where c.catid = p.category
and p.productid = i.productid
and i.itemid = v.itemid
</select>
> N+1 Select statements
> ---------------------
>
> Key: IBATIS-27
> URL: http://nagoya.apache.org/jira/browse/IBATIS-27
> Project: iBatis for Java
> Type: Improvement
> Components: SQL Maps
> Versions: 2.0.8
> Reporter: Raymod Zhang
>
> This issue has been brought up a few time before. But since it is such an
> important one, I have to post over here again to serve as a reminder.
> Original post by Clinton in Sourceforge:
> *******************BEGIN OF QUOTE***************************
> Amidst the many messages of the other two threads, this topic might have
> become fuzzy. The other two threads were largely dealing with syntax and
> schema changes to reduce the verbosity around joins that included duplicate
> column names.
>
> This had nothing to do with the N+1 selects solution.
>
> iBATIS already has an N+1 solution for 1:1 relationships (nested bean prop
> syntax w/join). It's very simple and not verbose at all. Duplicate column
> names are easily resolved using SQL aliases.
>
> As for the N+1 solution for 1:M and M:N, these are documented thoroughly in
> the Developer Guide. It clearly states in the developer guide that a solution
> for this is coming. 2.0 was designed from the start to handle this and it
> won't be a difficult change.
>
> Gilles and I have briefly discussed the XML stanzas and/or attributes that
> we'll need to add for this. It's simply a matter of making a choice. The
> community will be involved with making that choice. We'll hopefully get the
> alternatives posted here soon.
> **********************END OF QUOTE************************
> I am willing to help out if you guys need hands. Rather than waiting and
> complaiting, I'm ok to do it myself :) But first thing I need to confirm is
> the approach. Maybe clinton can enlighten me here.
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