Hi Paul,
Somendra Paul wrote:
Hi All, I am using OJB1.4 against Oracle10g with classes12.jar. We
are trying to export data from the DB, using SQL query which returns
600000 records , what we found out that is when we do iterator =
query.getIteratorByQuery(),and iterate over the results, we find
that after iterating over 300000 records, the VM grows rapidly and
the entire program crashes giving OOM errors, where as when we used
simple JDBC program to implement it, we saw that the entire 600K
records were extracted using only 160mb of memory , and the ojb
execution takes more than 1.5gb to execute before crashing.
Do we know how to solve this memory issue when executing large
resultset in Oracle.
One solution that in the OJB archives for ProgressSQL is that to use
fetchSize=<somevalue> , it will solve this issue ???
The problem could be the cache. Dependent on the used cache OJB keep all
materialized objects (or copies of these objects) in memory. Most cache
implementations use soft-references (so OOM errors shouldn't occur) but
maybe your objects have complex relationships or your layer holds
hard-references to the materialized objects.
You can try to evict the cache while iterate the result set.
If you don't rely on the materialized java objects you can use a report
query
http://db.apache.org/ojb/docu/guides/query.html#Report+Queries
to iterate over the result set (returns a collection of arrays). This
bypass the cache and should result in a memory-use comparable with a
plain jdbc-query.
The upcoming OJB 1.0.5 has enhanced query features and supports limit
and pagination of query results (Oracle is supported) - 1.0.5rc1:
http://www.mail-archive.com/ojb-user%40db.apache.org/msg16078.html
The query-guide of the included documentation show how to use this feature.
regards,
Armin
Thanks and Regards Somendra Paul.
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