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Hibernate HQL optimization
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created by <a href="http://community.jboss.org/people/csab79">csab79</a> in <i>EJB3</i> - <a href="http://community.jboss.org/message/585768#585768">View the full discussion</a>
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<div class="jive-rendered-content"><p>hello Hibernate gurus! </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I would like to improve my app performance through HQL optimzation. </p><p><br/>I have a small example to show my problem: </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><?xml version="1.0"?></p><p><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"</p><p><span>"</span><a class="jive-link-external-small" href="http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd" target="_blank">http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd</a><span>"></span></p><p><hibernate-mapping></p><p>    <class name="hibernate.classes.Peoples" table="PEOPLES" catalog="Dev1"></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>            <id name="PId" type="int"></p><p>                <column name="P_ID" /></p><p>                <generator class="identity"/></p><p>            </id></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>            <property name="pfirstname" type="string"></p><p>                <column name="p_firstname" /></p><p>            </property></p><p>            <property name="plastname" type="string"></p><p>                <column name="p_lastname" /></p><p>            </property></p><p>            <property name="phobby" type="string"></p><p>                <column name="p_hobby" /></p><p>            </property></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>          <many-to-one name="address" class="hibernate.classes.Address" fetch="join" insert="false" update="false"></p><p>                      <column name="p_adress" not-null="true"/></p><p>                  </many-to-one></p><p></class></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"</p><p><span>"</span><a class="jive-link-external-small" href="http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd" target="_blank">http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd</a><span>"></span></p><p><hibernate-mapping></p><p>    <class name="hibernate.classes.Address" table="ADDRESS" catalog="Dev1"></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>            <id name="AId" type="int"></p><p>                <column name="A_ID" /></p><p>                <generator class="identity"/></p><p>            </id></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>            <property name="street" type="string"></p><p>                <column name="a_street" /></p><p>            </property></p><p>            <property name="house" type="string"></p><p>                <column name="a_house" /></p><p>            </property></p><p>            <property name="district" type="string"></p><p>                <column name="a_district" /></p><p>            </property></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p></class></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I'd like to display rows from people and also show the appropriate person's address (foreign key bind) </p><p>When i use HQL join like this way: </p><p>session.createQuery("from  Peoples inner join Address") </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I suppose in this case .tolist() does not work properly becouse there are additional join properties. </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>When i use simple ("from Peopes") HQL query together with many-to-one default lazy="proxy" the result <br/>will be terrible slow. <br/>Hibernate try to gets seperatly every row from Address with foreign key selects. (May is it the N+1 Select problem?) </p><p>This is an impact when i have many rows in my table. </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>What is the best practice when i always want to display this cross joined datas?  </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>(pfirstname, plastname, phobby, street, house)</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Should i use iterator and manually place each property from the query result? </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><br/>Thanks in advance! <br/>Sorry for the dummy question! :S   </p></div>
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