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From Ing. Jan Novotný <novotn...@gmail.com>
Subject Re: Multiple selects per lazy loaded objects?!
Date Fri, 19 Feb 2010 05:14:42 GMT
Thanks - I thought that this is (was) a bug.

Jan

2010/2/19 Clinton Begin <clinton.begin@gmail.com>

> That might have been a bug just recently fixed.  Try out the trunk.  The
> lazy loader was heavily optimized for both performance and memory usage.
>
> Clinton
>
> 2010/2/18 Ing. Jan Novotný <novotnaci@gmail.com>
>
>> Thank you for answer. I understand now why all data were loaded at the
>> first touch to the object and not at time when particular property is
>> needed. But I still don't undestand why iBatis make two same select queries
>> to the database (see the log please) - this might hit a performance in some
>> cases. I still don't see the point.
>> Thanks.
>>
>> Jan
>>
>> 2010/2/18 Clinton Begin <clinton.begin@gmail.com>
>>
>>> This was a topic of much debate.  It does that to allow internal
>>> references to private fields.  But some people don't like that behavior, so
>>> in the next release (or in trunk if you want to check it out and build it),
>>> there's a configuration switch.  The docs are already updated, so look for
>>> the aggressiveLazyLoad setting.
>>>
>>>
>>> Clinton
>>>
>>> 2010/2/18 Ing. Jan Novotný <novotnaci@gmail.com>
>>>
>>>> Hello again,
>>>>
>>>>
>>>>    I've found that for lazily loaded objects triggers multiple
>>>> unnecessary selects and are executed all at load time not at the time, when
>>>> I touch the property. I use 3-beta-9 and my settings are following:
>>>>
>>>> <settings>
>>>>         <setting name="cacheEnabled" value="true"/>
>>>>         <setting name="lazyLoadingEnabled" value="true"/>
>>>>         <setting name="multipleResultSetsEnabled" value="true"/>
>>>>         <setting name="useColumnLabel" value="true"/>
>>>>         <setting name="useGeneratedKeys" value="false"/>
>>>>     </settings>
>>>>
>>>> <resultMap id="thinProductLazyLoaded" type="product">
>>>>         <id property="id" column="id"/>
>>>>         <result property="name" column="name"/>
>>>>         <association property="group" column="idGroup" javaType="group"
>>>>
>>>> select="cz.novoj.ibatis.ProductGroupMapper.getGroupById"/>
>>>>     </resultMap>
>>>>
>>>> <select id="getLazyProductById" parameterType="int"
>>>> resultMap="thinProductLazyLoaded">
>>>>         select * from product where id = #{id}
>>>>     </select>
>>>>
>>>> <select id="getGroupById" parameterType="int" resultType="group">
>>>>         select * from productGroup where id = #{id}
>>>>     </select>
>>>>
>>>>    Test:
>>>>
>>>> @Test
>>>>     public void testGetLazyProductById() throws Exception {
>>>>         Product product = productMapper.getLazyProductById(1);
>>>>         assertNotNull(product);
>>>>         System.out.println("#1");
>>>>         assertEquals(1, (int)product.getId());
>>>>         System.out.println("#2");
>>>>         assertEquals("Lenovo ThinkCentre 250GB Serial ATA Hard Disk
>>>> Drive", product.getName());
>>>>         assertNotNull(product.getGroup());
>>>>         System.out.println("#3");
>>>>         assertEquals("HDD", product.getGroup().getName());
>>>>         assertEquals("HARDWARE", product.getGroup().getGroupType());
>>>>         assertNull(product.getTags());
>>>>     }
>>>>
>>>>    Output:
>>>>
>>>> DEBUG [main][2010-02-18 14:42:34,140][java.sql.Connection]: ooo
>>>> Connection Opened
>>>> DEBUG [main][2010-02-18 14:42:34,234][java.sql.PreparedStatement]: ==>
>>>> Executing: select * from product where id = ?
>>>> DEBUG [main][2010-02-18 14:42:34,234][java.sql.PreparedStatement]: ==>
>>>> Parameters: 1(Integer)
>>>> DEBUG [main][2010-02-18 14:42:34,250][java.sql.ResultSet]: <==
>>>> Columns: ID, NAME, IDGROUP
>>>> DEBUG [main][2010-02-18 14:42:34,250][java.sql.ResultSet]: <==
>>>> Row: 1, Lenovo ThinkCentre 250GB Serial ATA Hard Disk Drive, 1
>>>> DEBUG [main][2010-02-18 14:42:34,359][java.sql.Connection]: xxx
>>>> Connection Closed
>>>> #1
>>>> DEBUG [main][2010-02-18 14:42:34,375][java.sql.Connection]: ooo
>>>> Connection Opened
>>>> DEBUG [main][2010-02-18 14:42:34,375][java.sql.PreparedStatement]: ==>
>>>> Executing: select * from productGroup where id = ?
>>>> DEBUG [main][2010-02-18 14:42:34,375][java.sql.PreparedStatement]: ==>
>>>> Parameters: 1(Integer)
>>>> DEBUG [main][2010-02-18 14:42:34,375][java.sql.ResultSet]: <==
>>>> Columns: ID, NAME, GROUPTYPE
>>>> DEBUG [main][2010-02-18 14:42:34,375][java.sql.ResultSet]: <==
>>>> Row: 1, HDD, HARDWARE
>>>> DEBUG [main][2010-02-18 14:42:34,390][java.sql.Connection]: xxx
>>>> Connection Closed
>>>> DEBUG [main][2010-02-18 14:42:34,390][java.sql.Connection]: ooo
>>>> Connection Opened
>>>> DEBUG [main][2010-02-18 14:42:34,390][java.sql.PreparedStatement]: ==>
>>>> Executing: select * from productGroup where id = ?
>>>> DEBUG [main][2010-02-18 14:42:34,390][java.sql.PreparedStatement]: ==>
>>>> Parameters: 1(Integer)
>>>> DEBUG [main][2010-02-18 14:42:34,390][java.sql.ResultSet]: <==
>>>> Columns: ID, NAME, GROUPTYPE
>>>> DEBUG [main][2010-02-18 14:42:34,390][java.sql.ResultSet]: <==
>>>> Row: 1, HDD, HARDWARE
>>>> DEBUG [main][2010-02-18 14:42:34,390][java.sql.Connection]: xxx
>>>> Connection Closed
>>>> #2
>>>> #3
>>>>
>>>>    Could someone explain how lazy really loading works? As I see, the
>>>> lazy loading paradigm has changed a lot since iBatis 2.x
>>>>
>>>> Jan
>>>>
>>>> --
>>>> --------------------------------------------------------------
>>>> Ing. Jan Novotný
>>>> @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
>>>> http://blog.novoj.net
>>>> Myšlenky dne otce Fura
>>>> --------------------------------------------------------------
>>>>
>>>
>>>
>>
>>
>> --
>> --------------------------------------------------------------
>> Ing. Jan Novotný
>> @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
>> http://blog.novoj.net
>> Myšlenky dne otce Fura
>> --------------------------------------------------------------
>>
>
>


-- 
--------------------------------------------------------------
Ing. Jan Novotný
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
http://blog.novoj.net
Myšlenky dne otce Fura
--------------------------------------------------------------

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