Andreas Bohnert 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 is no possibility to do this with ojb's getIteratorByQuery! Or is
there?
I had a look around, and you can currently not control this in OJB.
However, it is easy enough to issue this in the PostgreSQL-specific
platform driver but then it would apply to all created Statement
instances within OJB.
I will do some performance testing and run the regression test with vs.
without different setFetchSize settings in the PostgreSQL platform
and see if it qualifies as a new PostgreSQL default behaviour.
Any heads-up comments on this?
Regards,
Martin
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