Hi Eric and Roger,
checked in the initial version of native limit/offset support in CVS
(OJB_1_0_RELEASE branch). In class PaginationTest you can find example/tests
http://svn.apache.org/viewvc/db/ojb/branches/OJB_1_0_RELEASE/src/test/org/apache/ojb/broker/PaginationTest.java?view=markup
I run these tests again hsql, mysql, maxDB(get some failures, because of
driver bug) and oracleXE.
Native limit/offset support is implemented only for the most popular
databases - see ...broker.platforms.Platform classes source code. If you
need support for other database feel free to send patches ;-)
Please, if you can spend time give it a try.
regards,
Armin
Janssen, Roger wrote:
Hi,
The limit support can't substitute the real "native based" pagination.
My thought was to combine current OJB-pagination with new limit support
and
fetch-size - e.g set limit to 300, Query.setStartAtIndex(150),
Query.setEndAtIndex(300) to get results 150...300 and fetch-size=30 set
to
web-page result number size. This isn't perfect, but I think this will
be much more effective on large result sets as current behavior
(without limit).
Suggested solution only results in improved performance iterating over
the first pages. Nearing the end of the (large) resultset, performance
issues will rear their ugly head again. But.... in real the world, this
might work, since i do not believe people will iterate over manymanymany
pages to get to the end of a large resultset. When searching, they would
narrow their search criteria, for picklists, they would enter filter
criteria like startswith to narrow down the resultset, so if fetching
the first pages of a large resultset will have good performance, it
think your solution might actually solve this problem in the real world
You are right, native pagination support will be much more complex to
implement than limit support (your examples point out the problem).
But isn't it in most cases a simple sql-string split to integrate
the paging query string?
Yeah... It boils down to sql string manipulation, but before using OR
mappers, I had to do this in my applications myself and I remember it
being a pain to get it to work with all the supported databases.
Roger Janssen
iBanx
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