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Is <key not-null="true" ... /> available?

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orientphoebus

Post subject: Is <key not-null="true" ... /> available?

Posted: Thu Sep 22, 2005 12:19 am

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Joined: Thu Dec 02, 2004 10:42 am
Posts: 54

I am having a <list> relationship with one-to-many, like this:

Code:

<class name="Vector" table="VECTORS">
      <jcs-cache usage="read-write"/>
      <id name="DataID" column="ID" type="Int64" unsaved-value="0">
            <generator class="sequence">
                <param name="sequence">EQ.APP_SEQ</param>
            </generator>
      </id>
      <property name="Name" column="NAME" type="AnsiString" length="30"  access="field"/>
      <property name="LineColor" column="LINE_COLOUR" type="AnsiString" length="30" access="field"/>
      <property name="LineStyle" column="LINE_STYLE" type="AnsiString" length="30"  access="field"/>
      <property name="PointStyle" column="POINT_STYLE" type="AnsiString" length="30" access="field"/>
      <list name="Algorithms" table="INVOKED_ALGORITHMS" lazy="true" access="field" cascade="all">
         <jcs-cache usage="read-write" />
         <key column="VCTR_ID"/>
         <index column="EXECUTION_ORDER" type="Int32" length="1"/>
         <one-to-many class="InvokedAlgorithm" />
      </list>   
   </class>

The class InvokedAlgorithm is the class mapped to the same table "INVOKED_ALGORITHMS", with a ID column mapped to it's <id>

When removing a child from the list of "Algorithms", NHibernate actually update the left records' column of VCTR_ID & EXECUTION_ORDER to null first, then re-set them back with EXECUTION_ORDER has new value. For the 2 columns in our table is not nullable, this 2-step modifying causes problem in my case.

Why don't NHibernate just update the records with new value without doing null first?

I found a similar FAQ in Hibernate website:
http://www.hibernate.org/116.html#A7

This not-null attrb for <key> seems in Hibernate 3 only? Will it prevent Hibernate to set the column to null first then set it back?

How about <index>? Shall it have a "not-null" also?

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orientphoebus

Post subject: I really need help for this one.

Posted: Thu Sep 22, 2005 12:02 pm

Regular

Joined: Thu Dec 02, 2004 10:42 am
Posts: 54

The Parent-Child relation ship set in our database is not allow a child with no parent, that means the <key> column cannot be nullable. And I think this is a very common contrain many systems have.

But with this case, the NHibernate always try to break the relationship by setting the parent_id column to null first before deleting. This has driven our DBA crazy, he won't allow to set the column nullable, cause he think it breaks the data integrety. Although I explain him NHibernate handle this two steps in one transaction, it won't be a problem.

But Still, I'd like to have the <key not-null.....> attribute so that NHibernate can know what to do when deleting a child of <list>

Not just deleting, for insert in a <list> relationship, NHibernate update the rows to null and then update to the new index number. Don't you guys think its in-efficient? why not just update in the first shot.

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