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From "Kathey Marsden (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4055) Space may not be reclaimed if locks are not available after three retries (code inspection)
Date Fri, 13 Feb 2009 17:54:59 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4055?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12673325#action_12673325
] 

Kathey Marsden commented on DERBY-4055:
---------------------------------------

I looked at one of the test cases that triggered my assertion,  P703.  In this case the test
drops the container before commit.
if (segment != ContainerHandle.TEMPORARY_SEGMENT) {
			t_util.t_dropContainer(t, segment, cid);	// cleanup
		}

		t.commit();

So I think that's why we give up.  I don't really see how I could emulate this in JDBC and
it would be the lock case that I would want to trigger anyway.  So, I don't think this unit
test gives me a clue how to reproduce the  "  gave up after 3 tries to get container lock
" case with JDBC.






> Space may not be reclaimed if locks are not available after three retries (code inspection)
> -------------------------------------------------------------------------------------------
>
>                 Key: DERBY-4055
>                 URL: https://issues.apache.org/jira/browse/DERBY-4055
>             Project: Derby
>          Issue Type: Bug
>          Components: Store
>    Affects Versions: 10.1.3.1, 10.2.2.0, 10.3.3.0, 10.4.2.0, 10.5.0.0
>            Reporter: Kathey Marsden
>         Attachments: derby.log.T_RawStoreFactoryWithAssert
>
>
> I don't have a reproduction for these cases but there are two places in ReclaimSpaceHelper
where reclamation will give up after three tries if it cannot obtain the lock to reclaim the
space.  The first code path is:
> ContainerHandle containerHdl = 
> 			openContainerNW(tran, container_rlock, work.getContainerId());
> 		if (containerHdl == null)
> 		{
> 			tran.abort();
> 			if (SanityManager.DEBUG)
>             {
>                 if (SanityManager.DEBUG_ON(DaemonService.DaemonTrace))
>                 {
>                     SanityManager.DEBUG(
>                         DaemonService.DaemonTrace, " aborted " + work + 
>                         " because container is locked or dropped");
>                 }
>             }
> 			if (work.incrAttempts() < 3) // retry this for serveral times
>             {
> 				return Serviceable.REQUEUE;
>             }
> 			else
>             {
>                 // If code gets here, the space will be lost forever, and
>                 // can only be reclaimed by a full offline compress of the
>                 // table/index.
>                 if (SanityManager.DEBUG)
>                 {
>                     if (SanityManager.DEBUG_ON(DaemonService.DaemonTrace))
>                     {
>                         SanityManager.DEBUG(
>                             DaemonService.DaemonTrace, 
>                             "  gave up after 3 tries to get container lock " + 
>                             work);
>                     }
>                 }
> 				return Serviceable.DONE;
>             }
> 		}	
> the second is:
> 	RecordHandle headRecord = work.getHeadRowHandle();
> 		if (!container_rlock.lockRecordForWrite(
>                 tran, headRecord, false /* not insert */, false /* nowait */))
> 		{
> 			// cannot get the row lock, retry
> 			tran.abort();
> 			if (work.incrAttempts() < 3)
>             {
> 				return Serviceable.REQUEUE;
>             }
> 			else
>             {
>                 // If code gets here, the space will be lost forever, and
>                 // can only be reclaimed by a full offline compress of the
>                 // table/index.
>                 if (SanityManager.DEBUG)
>                 {
>                     if (SanityManager.DEBUG_ON(DaemonService.DaemonTrace))
>                     {
>                         SanityManager.DEBUG(
>                             DaemonService.DaemonTrace, 
>                             "  gave up after 3 tries to get row lock " + 
>                             work);
>                     }
>                 }
> 				return Serviceable.DONE;
>             }
> 		}
> If working to get a reproduction for these cases, you can set derby.debug.true=DaemonTrace
and look for "gave up" in the derby.log.

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