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https://issues.apache.org/jira/browse/OPENJPA-2416?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13724937#comment-13724937
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Andreas Mader commented on OPENJPA-2416:
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Wouldn't it be better, if you get correct data all the time (with and without
unique ordering)? My solution provides this...
We use Paging and Sorting in JSF-Datatables (Primefaces) - if the user takes a
column which is not unique as orderby-column, he gets a problem, he sees some
data twice and some data never. The only solution would be to add a unique
column to every request, also if there is no ordering applied by the user!
> setFirstResult/setMaxResults (Paging) with Oracle
> -------------------------------------------------
>
> Key: OPENJPA-2416
> URL: https://issues.apache.org/jira/browse/OPENJPA-2416
> Project: OpenJPA
> Issue Type: Improvement
> Components: query
> Affects Versions: 2.1.1
> Reporter: Andreas Mader
>
> We are using OpenJPA with Oracle 11g Database. For Paging we use
> setFirstResult and setMaxResults to Page through the result set.
> Lets take an example: PageSize 25.
> first Statement: firstResult: 0; maxResults: 26 (1 more to check if it is
> truncated)
> SQL generated:
> SELECT * FROM ([my statement]) WHERE ROWNUM <= 26
> second Statement: firstResult: 25; maxResults: 26
> SQL generated:
> SELECT * FROM (SELECT r.*, ROWNUM RNUM FROM ([my statement]) r WHERE ROWNUM
> <= 50) WHERE RNUM > 25
> The way limiting the resultset for paging is sometimes not correct. The last
> result of the statement should be equal to the first result of the new page -
> but it isn't always. If the sorting is done on a non-unique column in the
> database, there are different sortings in the resultset of these two
> statements. I don't know why it is done this way, I would prefer the
> following statement (this works for all values of firstResult and maxResults
> with non-unique sort column):
> SELECT outer.* FROM (
> SELECT ROWNUM rn, inner.* FROM
> ([my statement])
> inner)
> outer WHERE outer.rn > 25 AND outer.rn <= 50
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