[hibernate-issues] [Hibernate-JIRA] Issue Comment Edited: (HHH-2666) subselect fetching ignores max results

[umanath kandhallu (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-2666?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=45193#comment-45193 ] 

umanath kandhallu edited comment on HHH-2666 at 1/19/12 11:29 PM:
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i used following as a work around, where i set 200 as maxResults in parent criteria query.

i defined parent child @OneToMany with in below fashion instead of using subselect:

@Fetch(FetchMode.JOIN)
@BatchSize(size=200)


hibernate used subquery to fetch child records like one below:

select * from child where parentid in (?,?,?...)
instead of
select * from child where parentid in (criteria query which used to select parent)


      was (Author: umanathkm at gmail.com):
    i used following as a work around

@Fetch(FetchMode.JOIN)
@BatchSize(size=200)

so the generated query was like

select * from child where parentid in (?,?,?...)

instead of

select * from child where parentid in (criteria query which used to select parent)

  
> subselect fetching ignores max results
> --------------------------------------
>
>                 Key: HHH-2666
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2666
>             Project: Hibernate ORM
>          Issue Type: Improvement
>          Components: query-hql, query-sql
>    Affects Versions: 3.2.1, 3.5.3
>         Environment: Hibernate 3.2.1
> HSQLDB 8.0
>            Reporter: James Roper
>            Priority: Minor
>         Attachments: TestHibernateSubselect.java
>
>
> When maxResults is set for a query, the hibernate subselect fetching strategy ignores it.  For example, I have a class entry, that has a list of comments, which are configured to use the subselect fetching strategy.  You can see that in the original query, only the top ? results are fetched:
>     select
>         top ? entry0_.id as id0_,
>         entry0_.title as title0_,
>         entry0_.entry as entry0_,
>         entry0_.time as time0_,
>         entry0_.category_id as category5_0_ 
>     from
>         Entry entry0_ 
>     order by
>         entry0_.time desc
> But then when it does the sub select query to lazily load the comments, this is the query it runs:
>     select
>         comments0_.entry_id as entry5_1_,
>         comments0_.id as id1_,
>         comments0_.id as id1_0_,
>         comments0_.time as time1_0_,
>         comments0_.comment as comment1_0_,
>         comments0_.author as author1_0_ 
>     from
>         Comment comments0_ 
>     where
>         comments0_.entry_id in (
>             select
>                 entry0_.id 
>             from
>                 Entry entry0_ 
>         ) 
>     order by
>         comments0_.time desc
> So, it loads every single comment in the database, even though only the comments for the top ? entries are needed.  Of course, if there was no order by clause on the first query, the sub select may not return the same results, so it should probably only do this when there is an order by clause in the first query, and it should make sure it includes the order by clause in the sub select.

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