On Mon, 12 Sep 2005, Scott Eade wrote:
Therefore I am inclined to follow the proposed solution and throw an
exception in the constructor of LargeSelect if the chosen DB does not
support native limit and offset.
...
Are there any objections ? Is everybody ok with throwing a
RuntimeException, or would it be better to add the TorqueException to
the throws clause, possibly breaking people's code because
TorqueException is not caught ?
My only comment would be that as a heavy user of LargeSelect, if I were
to ever switch to a database that did not support limit and offset I
could not easily produce an executing (though obviously poorly
performing when it comes to LargeSelect) version of my application.
I would prefer us to add an appropriately worded statement in the docs
and javadocs highlighting the issue with a recommendation that it not be
used for the affected databases.
The comment already exists, though maybe one could highlight it more. The
problem is that the performance is much poorer
than it need be, because fetching one page at a time is exactly the thing
you should not do if you do not have native limit/offset.
Thinking over it again, the real solution would be to fetch the whole
memoryLinit at once and do the offset by hand if the database does not
support native limit/offset. The bad thing is that I do not know the
LargeSelect code and have not the time to do it at the moment (sigh).
I would also guess that the problems with databases which do not
support native limit/offset have lead to the exclusion of the
LargeSelectTest from the runtimetest. Does anybody object to include
the LargeSelectTest and print an error but not execute the test if the
database dose not support native limit/offset ? Sample code would be
public class LargeSelectTest extends BaseRuntimeTestCase
{
....
public void testLargeSelect() throws TorqueException
{
if (Torque.getDB(Torque.getDefaultDB()).getLimitStyle()
== DB.LIMIT_STYLE_NONE)
{
log.error("LargeSelect is known not to work for databases "
+ "which do not support native limit/offset");
return;
}
....
If one adds this, the LargeSelectTest also runs for hsqldb which does
not support native limit/offset.
Does the test case fail at present?
At the moment, the method LargeSelectTest.testLargeSelect() fails.
If we continue to let the code code
execute for the reason given above then the test case should at least be
enabled to make sure that the simulated limit and offset are indeed
compatible with the behaviour when the database supports them.
If we manage to do the limit/offset manually, one could take it out again.
Thomas
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