[DERBY-4055] Space may not be reclaimed if row locks are not available after three retries

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 10.1.3.1, 10.2.2.0, 10.3.3.0, 10.4.2.0, 10.5.1.1
• Component/s: Store
• Labels: derby_triage10_11
• Urgency: Normal
• Issue & fix info: High Value Fix, Workaround attached
• Assignee: Unassigned
• Reporter: Katherine Marsden
• Created: 12/Feb/09 19:41
• Updated: 03/Jul/13 15:26

Description

In a multithreaded clob update where the same row is being updated, space will not be reclaimed. The offending code is in ReclaimSpaceHelper:

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 we cannot get the lock after three tries we give up. The reproduction for this issue is in the test store.ClobReclamationTest.xtestMultiThreadUpdateSingleRow().


This issue also used to reference the code below and has some references to trying to get a reproduction for that issue, but that work has moved to DERBY-4054. Please see DERBY-4054 for work on the container lock issue.

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;
}
}

Issue Links

• is related to: DERBY-4050 Multithreaded clob update causes growth in table that does not get reclaimed
• is related to: DERBY-5356 Tracking for Derby space reclamation issues
• is related to: DERBY-5876 Overhaul table compression code