btree post commit releases latch before committing/aborting purges, possibly
allowing other operation on page
-------------------------------------------------------------------------------------------------------------
Key: DERBY-5258
URL: https://issues.apache.org/jira/browse/DERBY-5258
Project: Derby
Issue Type: Bug
Components: Store
Affects Versions: 10.8.1.2, 10.7.1.1, 10.6.1.0, 10.5.3.0, 10.4.2.0,
10.3.3.0, 10.2.2.0, 10.1.3.1
Reporter: Mike Matrigali
Assignee: Mike Matrigali
>From code inspection found the following problem.
>BTreePostCommit.purgeCommittedDeletes gives up the latch in it's finally
>block, before the internal transaction is
committed. The transaction is committed no sync upon return from this routine
leaving a very small window when some other thread could get latch on the page
and
perform operations on the page.
This can be a problem if for some reason the internal transaction is never
committed. Purges actually return space to the page, unlike deletes. In order
to backout the
purges one must add the rows back, taking up space on the page. If another
tranaction comes in before the internal transaction is committed and does
inserts there may
be no space for the backout of the purges. This is why normal delete
processing only sets flags on the rows and purge processing is handled
differently.
I found this problem while debugging a database submitted as part of
DERBY-5248. I believe this issue can cause the problem there, but since we
have no repro have
decided to create a new issue to target this specific problem/solution. Later
can close the other issue if it can never be reproduce after the fix. In
DEBY-5248 there
are purges without a commit followed immediated by an insert in another
transaction that is commited and the purge transaction is never committed. On
recovery the
system tries to abort the internal transaction and eventually trashes the page
when it does not actually have enough space to abort the purge. See that issue
for more
detail.
--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira
