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Commit059f30c

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Properly terminate the array returned by GetLockConflicts().
GetLockConflicts() has for a long time not properly terminated thereturned array. During normal processing the returned array is zeroinitialized which, while not pretty, is sufficient to be recognized asa invalid virtual transaction id. But the HotStandby case is more thanaesthetically broken: The allocated (and reused) array is neitherzeroed upon allocation, nor reinitialized, nor terminated.Not having a terminating element means that the end of the array willnot be recognized and that recovery conflict handling will thus readahead into adjacent memory. Only terminating when hitting memorycontent that looks like a invalid virtual transaction id. Luckilythis seems so far not have caused significant problems, besides makingrecovery conflict more expensive.Discussion: 20150127142713.GD29457@awork2.anarazel.deBackpatch into all supported branches.
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  • src/backend/storage/lmgr

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‎src/backend/storage/lmgr/lock.c

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@@ -1944,6 +1944,8 @@ GetLockConflicts(const LOCKTAG *locktag, LOCKMODE lockmode)
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* on this lockable object.
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*/
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LWLockRelease(partitionLock);
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vxids[count].backendId=InvalidBackendId;
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vxids[count].localTransactionId=InvalidLocalTransactionId;
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returnvxids;
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}
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@@ -1989,6 +1991,8 @@ GetLockConflicts(const LOCKTAG *locktag, LOCKMODE lockmode)
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if (count>MaxBackends)/* should never happen */
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elog(PANIC,"too many conflicting locks found");
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vxids[count].backendId=InvalidBackendId;
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vxids[count].localTransactionId=InvalidLocalTransactionId;
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returnvxids;
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}
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