[hibernate-issues] [Hibernate-JIRA] Updated: (HHH-3325) Pagination with Oracle ROWNUM is sub-optimal

[Seth Wilcox (JIRA)]

     [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-3325?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Seth Wilcox updated HHH-3325:
-----------------------------

    Attachment: OracleLimit.patch

Thanks Christian, I was able to overload getLimitString(String sql, int offset, int limit) to get the limit to replace n with.
Richard, that solution would cause the query to have to be run twice, not sure how good oracle would be at optimizing that away

Here is the patch for Oracle9iDialect.java correcting the FIRST_ROWS(n) problem

> Pagination with Oracle ROWNUM is sub-optimal
> --------------------------------------------
>
>                 Key: HHH-3325
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3325
>             Project: Hibernate Core
>          Issue Type: Bug
>    Affects Versions: 3.2.5
>            Reporter: e. wernli
>         Attachments: OracleLimit.patch, OracleLimit.patch
>
>
> Pagination with Oracle ROWNUM is sub-optimal
> The feature works but result in sub-optimal SQL. The generated SQL is the following:
> select * from ( select row_.*, rownum rownum_ from ( select this_.id as id3_0_, this_.version as version3_0_, this_.name as name3_0_, this_.type as type3_0_, this_.marketstatus as marketst5_3_0_ from Customer this_ order by this_.id asc ) row_ ) where rownum_ <= ? and rownum_ > ?
> But this SQL is faster:
> SELECT *
>   FROM (SELECT row_.*, ROWNUM rownum_
>           FROM (SELECT   this_.ID AS id3_0_, this_.VERSION AS version3_0_,
>                          this_.NAME AS name3_0_, this_.TYPE AS type3_0_,
>                          this_.marketstatus AS marketst5_3_0_
>                     FROM customer this_
>                 ORDER BY this_.ID ASC) row_
>          WHERE ROWNUM <= ?)
>  WHERE rownum_ > ?
> The second solution allows Oracle to use an optimization that can dramatically reduce the time of the query, especially one of the first page is retrieved.
> See this link for an explanation of this optimization: http://decipherinfosys.wordpress.com/2007/08/09/paging-and-countstopkey-optimization/

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