Martin Kal�n wrote:
Postgres (for example) don't use cursors on default. The PG jdbc
driver loads the entire ResultSet all at once and keeps it in memory!
So, even if you do a getIteratorByQuery the memory load on a large
resultset is huge!
You can get around this, if you set the fetchsize on the jdbc statement
for example:
stmt = con.createStatement();
stmt.setFetchSize(1);
ResultSet rs = stmt.executeQuery(sql);
This actually forces the jdbc driver to use a cursor and browse the
resultset one by one.
There was no regression when running the test suite with fetch size=1
(and it actually ran a tiny bit faster, presumably because of less
JVM allocations for objects not used in the tests).
I will re-run again and check peak JVM heap usage before/after and
bring it up on the development list.
Do you see any drawbacks of an OJB-global default of fetchSize=1
for PostgreSQL?
(This should not affect OJB proxy-prefetching-limit since that prefecthing
is done one layer above the PostgreSQL JDBC level.)
Regards,
Martin
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