Andreas Mader created OPENJPA-2416:
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Summary: 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 in 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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