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From "Tomi N/A" <hef...@gmail.com>
Subject OutOfMemoryError: reading a large number of objects one by one
Date Mon, 14 May 2007 17:57:01 GMT
I'll try to be to the point.
I need:
- to "stream" data from potentially large tables
- wan't the app to not use more than a couple of MB of RAM, as
(theoretically) there shouldn't be a reason for it to need any more

Using cayenne 1.2 something (no, switching to something a bit more
modern is not a high priority...yet).

Have tried with paginated query, failed.
Have tried with dc.performIteratedQuery(...), failed.
Have tried with a combination, failed.
Have tried various values of cayenne.DataRowStore.snapshot.size (10^3
to 10^5), failed.
Have not tried combining a low DataRowStore.snapshot.size value with
an iterated/paginated query.

This was the last (failed) attempt:

Expression condition = ExpressionFactory.matchExp(MyClassA.TO_B_PROPERTY, b);
		SelectQuery query = new SelectQuery(MyClassA.class, condition);
		query.setFetchLimit(10000);
		query.setPageSize(100);

		ResultIterator ri;
		try {
			ri = Util.getCommonContext().performIteratedQuery(query);
			MyClassA mca;
			while (ri.hasNextRow()) {
				DataRow dr = (DataRow) ri.nextDataRow();
				mca = (MyClassA)
Util.getCommonContext().objectFromDataRow(SpisUtil.class, dr, false);
				
				System.out.println(mca.getAttr1().toString());
				System.out.println(mca.getToMyClassC().getAttr3().toString());
			}
		} catch (CayenneException ex) {
			ex.printStackTrace();
		}

The fetch limit is only a temporary measure: I used it to deduce that
I run out of memory somewhere between a 1000 and 10000.
Now...I see no reason why it would be impossible to have a snippet of
code not unlike this one (working with a hand full of objects at any
given time) work with an arbitrarily large dataset and use no more
than 1MB of RAM, but I'll be generous and say it's great if it works
using under, say, 30MB. :)

Opinions, hints, suggestions, possibilities?

TIA,
t.n.a.

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