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jnapier
 Post subject: Lazy One to One
PostPosted: Sun Sep 11, 2005 9:11 pm 
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Posts: 178
I have a one to one relationship from one object to another(Member to JobPost). Both objects have the lazy attribute so they can be proxied.

When I query for the Member object an additional sql query is issued immediatly to load the JobPost which is specified as the one-to-one. Are my settings wrong? Is this a bug? I have abbreviated the mappings and listed them below.

Code:
<class name="Member" table="Member" lazy="true">
      <!--ID-->
      <id name="Id" column="MemberId" unsaved-value="0" access="nosetter.camelcase-underscore">
         <generator class="identity" />
      </id>
            
      
      <!--ASSOSCIATIONS-->
      <one-to-one name="JobPost" class="JobPost"  property-ref="StaffMember" access="nosetter.camelcase-underscore"  outer-join="true"  />
         
   </class>

<class name="JobPost" table="JobPost" lazy="true">      
      <!--ID-->
      <id name="Id" column="JobPostId" unsaved-value="0" access="nosetter.camelcase-underscore">
         <generator class="identity" />
               
      <!--ASSOSCIATIONS-->
      <many-to-one name="StaffMember" column="MemberId" class="Member"  access="nosetter.camelcase-underscore"  outer-join="true" unique="true" />
            
   </class>
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jnapier
 Post subject:
PostPosted: Sun Sep 11, 2005 9:27 pm 
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Joined: Sat Sep 10, 2005 3:46 pm
Posts: 178
Sorry, but actually in the mapping file above I have outer-join set to true. I was testing something at the time that I copied the mapping. The problem I am experiencing is occurring when the outer-join on the one to one mapping is false. Sorry about that. The actual mapping is listed below.

Code:
<one-to-one name="JobPost" class="JobPost"  property-ref="StaffMember" access="nosetter.camelcase-underscore"  outer-join="false"  />
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sergey
 Post subject:
PostPosted: Mon Sep 12, 2005 3:59 am 
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Joined: Wed May 11, 2005 4:59 pm
Posts: 1766
Location: Prague, Czech Republic
NHibernate won't use lazy-loading for one-to-one relationship, unless it has constrained="true", meaning the referenced object always exists. Otherwise, NHibernate needs to find out whether the object exists, to know whether to set the reference to null or to create a proxy for the object, and since it has to SELECT from a table to find that out, it can as well get the entire object data with that SELECT. NH assumes that selecting 10 fields from a table is about as expensive as selecting only one.
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jnapier
 Post subject:
PostPosted: Mon Sep 12, 2005 4:34 am 
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Joined: Sat Sep 10, 2005 3:46 pm
Posts: 178
Setting constrained="true" has no effect.

Atleast, since the one to one is a simple assosciation shouldnt it be able to be queried without having to issue a separate sql query?
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sergey
 Post subject:
PostPosted: Mon Sep 12, 2005 5:49 am 
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Posts: 1766
Location: Prague, Czech Republic
This page should give you more and better details: http://www.hibernate.org/162.html
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sergey
 Post subject:
PostPosted: Mon Sep 12, 2005 12:45 pm 
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Posts: 1766
Location: Prague, Czech Republic
Hmm, I guess this topic actually describes the problem: http://nhibernate.sourceforge.net/forum/viewtopic.php?p=2545
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jnapier
 Post subject:
PostPosted: Tue Sep 13, 2005 1:33 am 
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Joined: Sat Sep 10, 2005 3:46 pm
Posts: 178
Ok. So apparently it cant be lazy loaded. This still doesn't explain why an additional select statement is getting issued for the object. Its one to one so it should be coming down in one query right?
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