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Posted to user-java@ibatis.apache.org by Danny Lin <da...@trionworld.com> on 2008/04/03 19:30:39 UTC

n+1 selects and queryForMap

Hello,

I have an object with a property that is a HashMap of name/value pairs from a separate data table. If one of my properties on the 'food' class is a hashmap, I'm assuming I can create that hashmap using the following sql mapping correct?

Is it possible to avoid the n+1 select issue and solve this problem using another method? Would this be a case to use a row handler?

Thanks!


food
food_id            int
food_name      varchar(256)


food_attributes
food_id            int
name               varchar(64)
value               varchar(64)


<resultMap id="food" class="food" >
            <result property="foodId" column="food_id"/>
            <result property="foodName" column="food_name"/>
<result property="foodAttributes" select="getFoodAttributes"/>
</resultMap>


<resultMap id="foodAttributes " class="java.util.HashMap" >
               <result property="name" column="name"/>
               <result property="value" column="value"/>
</resultMap>

<select id="getFood" resultMap="food" parameterClass="int">
            select * from food where food_id=#id#
</select>

<select id="getFoodAttributes" resultMap="foodAttributes" parameterClass="int">
            select * from food_attributes where food_id=#id#
</select>


Danny

RE: n+1 selects and queryForMap

Posted by Danny Lin <da...@trionworld.com>.
Is this even a valid way to get a hashmap or do we need to use queryForMap?


<resultMap id="foodAttributes " class="java.util.HashMap" >
               <result property="name" column="name"/>
               <result property="value" column="value"/>
</resultMap>

<select id="getFoodAttributes" resultMap="foodAttributes" parameterClass="int">
            select * from food_attributes where food_id=#id#
</select>

From: Danny Lin [mailto:danny@trionworld.com]
Sent: Thursday, April 03, 2008 10:31 AM
To: user-java@ibatis.apache.org
Subject: n+1 selects and queryForMap

Hello,

I have an object with a property that is a HashMap of name/value pairs from a separate data table. If one of my properties on the 'food' class is a hashmap, I'm assuming I can create that hashmap using the following sql mapping correct?

Is it possible to avoid the n+1 select issue and solve this problem using another method? Would this be a case to use a row handler?

Thanks!


food
food_id            int
food_name      varchar(256)


food_attributes
food_id            int
name               varchar(64)
value               varchar(64)


<resultMap id="food" class="food" >
            <result property="foodId" column="food_id"/>
            <result property="foodName" column="food_name"/>
<result property="foodAttributes" select="getFoodAttributes"/>
</resultMap>


<resultMap id="foodAttributes " class="java.util.HashMap" >
               <result property="name" column="name"/>
               <result property="value" column="value"/>
</resultMap>

<select id="getFood" resultMap="food" parameterClass="int">
            select * from food where food_id=#id#
</select>

<select id="getFoodAttributes" resultMap="foodAttributes" parameterClass="int">
            select * from food_attributes where food_id=#id#
</select>


Danny