我有以下结构:消息(消息表)可能有多个字段(字段表),每个字段可能有多个子字段(存储在相同的“字段”表中,唯一的区别是字段中没有值“ParentField”栏目。子字段可能有子字段等,但这并不重要。
当我检索10条每条有10个字段的消息,每个字段有20个子字段时,我可以从日志文件中看到NHibernate生成2000个SQL调用。 有没有办法优化它?
谢谢!
这是NHibernate生成的2000个SQL语句之一:
SELECT fieldresul0_.MessageResults_ID as MessageR6___2_,
fieldresul0_.ID as ID2_,
fieldresul0_.ID as ID5_1_,
fieldresul0_.Field_ID as Field2_5_1_,
fieldresul0_.Name as Name5_1_,
fieldresul0_.Value as Value5_1_,
fieldresul0_.MessagePosition as MessageP5_5_1_,
fieldresul0_.MessageResults_ID as MessageR6_5_1_,
fieldresul0_.ParentField_ID as ParentFi7_5_1_,
fieldresul1_.ID as ID5_0_,
fieldresul1_.Field_ID as Field2_5_0_,
fieldresul1_.Name as Name5_0_,
fieldresul1_.Value as Value5_0_,
fieldresul1_.MessagePosition as MessageP5_5_0_,
fieldresul1_.MessageResults_ID as MessageR6_5_0_,
fieldresul1_.ParentField_ID as ParentFi7_5_0_
FROM FieldResults fieldresul0_
LEFT OUTER JOIN FieldResults fieldresul1_
ON fieldresul0_.ParentField_ID=fieldresul1_.ID
WHERE fieldresul0_.MessageResults_ID=@p0
ORDER BY fieldresul0_.MessagePosition
这是ActiveRecord生成的映射文件:
<?xml version="1.0" encoding="utf-16"?>
<hibernate-mapping auto-import="true" default-lazy="false" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="urn:nhibernate-mapping-2.2">
<class name="FieldResult, Data" table="FieldResults">
<id name="ID" access="property" column="ID" type="Int32" unsaved-value="0">
<generator class="native">
<param name="sequence">FieldResults_ID</param>
</generator>
</id>
<property name="FieldID" access="property" type="String">
<column name="Field_ID"/>
</property>
<property name="Name" access="property" type="String">
<column name="Name"/>
</property>
<property name="DisplayValue" access="property" type="String">
<column name="Value"/>
</property>
<property name="MessagePosition" access="property" type="Int32">
<column name="MessagePosition"/>
</property>
<many-to-one name="ParentMessage" access="property" class="MessageResult, Data" column="MessageResults_ID" />
<many-to-one name="ParentField" access="property" class="FieldResult, Data" column="ParentField_ID" />
<bag name="Children" access="property" table="FieldResults" lazy="false" cascade="all" order-by="Field_ID">
<key column="ParentField_ID" />
<one-to-many class="FieldResult, Data" />
</bag>
</class>
</hibernate-mapping>`
答案 0 :(得分:0)
我猜这是一个选择n + 1问题。您是否尝试过急切加载或自定义HQL查询?如果你没有
,我会发布一些示例HQL来解决这个问题答案 1 :(得分:0)
有一种方法可以帮助nhibernate执行更高效的连接。明确告诉查询处理器包含带有“join fetch”的查找表,并通过HQL和Session.CreateQuery()获取结果
from FieldRestults fr
left join fetch fr.ParentMessage
left join fetch fr.ParentField
在我正在调查的另一个问题中优化一个包。