[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-1952) HQL query that uses implicit polymorphism returns (# concrete classes x n) rows, not n rows, when setMaxResults(n) is used

[Steve Ebersole (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-1952?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=32065#action_32065 ] 

Steve Ebersole commented on HHH-1952:
-------------------------------------

And what would you like to see?  Since Hibernate fires off the "concrete queries" one-by-one, we cannot rely on simply passing setMaxResults through to the JDBC driver here.

The only solutions I see are:
1) Disallow setMaxResults in combo with implicit polymorphism queries;
2) Apply the setMaxResults in memory

> HQL query that uses implicit polymorphism returns (# concrete classes x n) rows, not n rows, when setMaxResults(n) is used
> --------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HHH-1952
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1952
>             Project: Hibernate Core
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 3.1.3
>         Environment: Hibernate: 3.1.3 
>            Reporter: David Donn
>
> If I have m mapped entities that implement the same interface and execute a polymorphic query with setMaxResults(n) I get n x m rows instead of n rows in my result.
> Query:
> session.createQuery("from Animal").setMaxResults(1)
> Hibernate mapping:
> 	<class
> 		name="Lion"
> 		table="lion" lazy="false">
> 		
> 		<id name="id">
> 			<generator class="sequence">
> 				<param name="sequence">animal_seq</param>
> 			</generator>
> 		</id>
> 				
> 	</class>
> 	
> 	<class
> 		name="Tiger"
> 		table="tiger" lazy="false">
> 		
> 		<id name="id">
> 			<generator class="sequence">
> 				<param name="sequence">animal_seq</param>
> 			</generator>
> 		</id>
> 				
> 	</class>
> Class definitions:
> public interface Animal {
> }
> public class Lion implements Animal {
>     private Long id;
>     public Long getId() {
>         return id;
>     }
>     public void setId(Long id) {
>         this.id = id;
>     }
>     
> }
> public class Tiger implements Animal {
>     private Long id;
>     public Long getId() {
>         return id;
>     }
>     public void setId(Long id) {
>         this.id = id;
>     }
>     
> }
> SQL:
> create sequence animal_seq start with 1
> /
> create table lion (id number(12) primary key)
> /
> create table tiger (id number(12) primary key)
> /
> insert into lion values (animal_seq.nextval)
> /
> insert into tiger values (animal_seq.nextval)
> /

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