[Hibernate-issues] [Hibernate-JIRA] Created: (HHH-1713) AbstractEntityPersister causes an exception when a row in a joined table is missing with fetch="select"

[Mike D. (JIRA) <no...@at...>]

AbstractEntityPersister causes an exception when a row in a joined table is missing with fetch="select"
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         Key: HHH-1713
         URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1713
     Project: Hibernate3
        Type: Bug

  Components: core  
    Versions: 3.1.3, 3.2.0 cr1    
 Environment: Hibernate 3.1.3, 3.2.0cr1
Oracle 9i (using odjbc14.jar from Oracle 10.1.0.4)
    Reporter: Mike Dillon
    Priority: Minor
 Attachments: AbstractEntityPersister.java.patch

When using the <join> mapping, the behavior of AbstractEntityPersister when the joined row is missing is not consistent between fetch="join" and fetch="select".

When fetch="join" and the row is missing, the AbstractEntityPersister simply sets all the outer joined fields to null since that's what comes back from the database. However, when fetch="select" and the row is missing, an SQLException is thrown. The reason is that the call to ResultSet.next() is not checked to see if a row is available before calling ResultSet.getXXXX(). In our Oracle enviroment, this resulted in a cryptic JDBC error about an "Exhausted Resultset".

The fix is to check the return value of ResultSet.next(). I have attached a patch with a proposed fix for this issue. To be consistent with the current behavior of fetch="join", it explicitly sets all fields that come from the "sequential select" to null when the select does not produce any rows. This contradicts the hibernate-mapping DTD which says that the "optional" attribute on <join> defaults to false, but since that attribute is undocumented and the current implementation doesn't seem to respect this attribute even when fetch="join", I decided to be consistent with the actual semantics of fetch="join".

The behavior of the optional attibute probably needs to be fixed in both cases, but I didn't address that with my patch. It seems that optional only works as advertised when Hibernate is able to produce a query with a single polymorphic join and can use an inner join instead of a left outer join.

My patch was created against Hibernate 3.1.3, but I looked at the same code in 3.2.0cr1 and it has not changed.

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