Possible bug in interaction with buffer manager causing pages not to be freed
on rollback to savepoint
------------------------------------------------------------------------------------------------------
Key: DERBY-3099
URL: https://issues.apache.org/jira/browse/DERBY-3099
Project: Derby
Issue Type: Bug
Components: Services, Store
Affects Versions: 10.4.0.0
Reporter: Knut Anders Hatlen
I noticed this strange behaviour when I was working on DERBY-2911. It seems
like the result of test case P042 in unit/T_RawStoreFactory.unit is dependent
on the actual contents of the buffer manager (which pages have been evicted,
which free entries have been reused and so on). I'm not sure if this is a bug
in the test or somewhere in the code, or if this is expected behaviour, but it
sounds a bit suspicious.
For instance, commenting out all the test cases preceeding P042 makes P042
fail, even though P042 creates a new container so that it should not be
affected by any of the previous test cases. Also, commenting out a space
optimization in Clock.findFreeItem() so that freed entries are not reused
except when rotateClock() is called on a full cache to find a victim, causes
the test case to fail. A third way to make it fail, is to vary the scan
direction when looking for a free entry to reuse in the new buffer manager
(ConcurrentCache). If the scan is disabled or walks the clock from the
beginning to the end, the test fails, but if the clock is scanned backwards, it
passes.
The code that fails in the test, is
c = t_util.t_openContainer(t, segment, cid, true);
Page checkNextPage = t_util.t_addPage(c);
if (checkNextPage.getPageNumber() == nextPageNumber)
throw T_Fail.testFailMsg(
"expect some pages to be freed by
update rollback");
The expected page number is 2, and the actual page number is 7.
Before this, a large row has been inserted on page 1 and overflows to page 2,
3, 4, 5 and 6. Also, page 7 has been added manually before all the updates were
rolled back so that the pages from 2 up to 7 should be unallocated. Page 7 is
then added and removed, and the transaction is committed. After reopening the
container, the test expects the pages from 2 up to 7 to be free, and that
t_addPage() should allocate page number 2.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
