[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-1615) GROUP BY entity does not work

[Tim Lüecke (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-1615?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_29468 ] 

Tim Lüecke commented on HHH-1615:
---------------------------------

At least Oracle 10g does not seem to have an optimizer smart enogh to discover the speed-up pattern you proposed. A query very similar to yours turned out to be quite more costly if you added just one more column to the select and the group by clause. The difference seems to be, that when only the ID is selected, no sort is performed.

> GROUP BY entity does not work
> -----------------------------
>
>                 Key: HHH-1615
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1615
>             Project: Hibernate3
>          Issue Type: Improvement
>          Components: query-hql
>    Affects Versions: 3.2.5
>         Environment: PostgreSQL 8.1.3, Hibernate 3.1.3
>            Reporter: Xavier Bugaud
>            Assignee: Anthony Patricio
>            Priority: Critical
>         Attachments: hibernate-group-by.diff
>
>
> The query : "select cat, count(*) from Cat cat group by cat" does not work.
> ERROR: column "xxxx" must appear in the GROUP BY clause or be used in an aggregate function
> See :
>  - http://forum.hibernate.org/viewtopic.php?t=953716
>  - http://jira.nhibernate.org/browse/NH-528

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