[英]How to tweak Hibernate queries
我不得不调试一些我未编写的休眠代码。 我会直截了当地承认我正在努力地了解Hibernate如何将查询整合到这一点,所以请多多包涵。
我们看到的问题是Web应用程序花费大量的时间来加载页面(使用JSP,Spring和Hibernate)。
正在执行的查询之一引用了一个映射中的公式,该公式似乎在休眠执行的查询中使用了两次。 第一个引用是列值,第二个引用用作内部联接的条件。 第二个是内部联接,它强制进行全表扫描,这是我们不需要的,更不用说它使查询真正变慢了。
有没有办法调整休眠查询,以使其不在查询中使用此公式(列值除外)? 请告知您是否需要其他信息。
编辑:根据要求,这是我从休眠记录中获取的查询:
SELECT this_.PARTY_ID AS PARTY1_23_2_,
this_.STUDENT_ID AS STUDENT3_23_2_,
this_.STUDENT_PIDM AS STUDENT4_23_2_,
this_.USERNAME AS USERNAME23_2_,
this_.FIRST_NAME AS FIRST6_23_2_,
this_.LAST_NAME AS LAST7_23_2_,
this_.ACTIVE AS ACTIVE23_2_,
subjectenr1_.PARTY_ID AS PARTY1_24_0_,
subjectenr1_.OFFERING_ID AS OFFERING2_24_0_,
subjectenr1_.RSTS_CODE AS RSTS3_24_0_,
subjectenr1_.SITE_CODE AS SITE4_24_0_,
subjectenr1_.PROGRAM_CODE AS PROGRAM5_24_0_,
(SELECT su2.offering_id
FROM sakaicfg.subject_offering su2
WHERE su2.offering_id = subjectenr1_.OFFERING_ID
) AS formula0_0_,
subjectoff2_.OFFERING_ID AS OFFERING1_25_1_,
subjectoff2_.CRN AS CRN25_1_,
subjectoff2_.IS_ACTIVE AS IS3_25_1_,
subjectoff2_.TEACHING_SCHOOL AS TEACHING4_25_1_,
subjectoff2_.CAMPUS AS CAMPUS25_1_,
subjectoff2_.START_SEMESTER AS START6_25_1_,
subjectoff2_.STUDYMODE AS STUDYMODE25_1_,
subjectoff2_.SUBJECT_ID AS SUBJECT8_25_1_,
subjectoff2_.GRADE_MARKING_CODE AS GRADE9_25_1_,
(SELECT MAX(su2.effective_semester)
FROM sakaicfg.subject su2
WHERE su2.subject_id = subjectoff2_.SUBJECT_ID
AND su2.effective_semester <= subjectoff2_.START_SEMESTER
) AS formula1_1_
FROM SAKAICFG.STUDENT this_
INNER JOIN SAKAICFG.SUBJECT_ENROLMENT subjectenr1_
ON this_.PARTY_ID=subjectenr1_.PARTY_ID
INNER JOIN SAKAICFG.SUBJECT_OFFERING subjectoff2_
ON (SELECT su2.offering_id
FROM sakaicfg.subject_offering su2
WHERE su2.offering_id = subjectenr1_.OFFERING_ID)=subjectoff2_.OFFERING_ID
WHERE this_.ACTIVE ='Y'
AND subjectenr1_.RSTS_CODE <>'DD'
AND subjectoff2_.IS_ACTIVE ='Y'
AND subjectoff2_.OFFERING_ID='35505'
ORDER BY this_.PARTY_ID DESC;
有问题的部分是以下摘录:
(SELECT su2.offering_id
FROM sakaicfg.subject_offering su2
WHERE su2.offering_id = subjectenr1_.OFFERING_ID
)
“主题注册”表的映射xml文件包含以下关系:
<many-to-one name="student" entity-name="CsuActiveStudentDto" column="PARTY_ID" insert="false" update="false" access="field" unique="false"/>
<many-to-one name="subjectOffering" entity-name="CsuSubjectOfferingDto" insert="false" update="false" access="field" unique="false">
<formula>(select su2.offering_id
from sakaicfg.subject_offering su2 where su2.offering_id = OFFERING_ID)</formula>
</many-to-one>
<one-to-one name="student" class="au.edu.csu.enterprise.domain.StudentDto" property-ref="enrolment"/>
<many-to-one name="offering" class="au.edu.csu.enterprise.domain.SubjectOfferingDto" column="OFFERING_ID"/>
我一直在与我们的一名DBA一起研究查询,并隔离那些需要研究的查询,这就是我们找到这一查询的方式。
您可以通过自定义SQL(而非hql)为每个实体(以及集合)覆盖Hibernate Create Read Update和Delete语句。
有关更多详细信息,请参见《 Hibernate参考: 第17.3章》。 在Hibernate Annotation Reference: 第2.4.10章中 ,用于创建,更新和删除以及其工作方式的自定义SQL 。 用于CRUD操作的自定义SQL
@Entity
@SQLInsert( sql="INSERT INTO Demo(name, id) VALUES(?,?)")
@Loader(namedQuery = "betterLoad")
@NamedNativeQuery(name="betterLoad",
query="select id, name from Demo where id= ?",
resultClass = Demo.class)
public class Demo {
@Id
private Long id;
private String name;
}
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