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Make CLUSTER lock the old table's toast table before copying data.

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We must lock out autovacuuming of the old toast table before computing the
OldestXmin horizon we will use.  Otherwise, autovacuum could start on the
toast table later, compute a later OldestXmin horizon, and remove as DEAD
toast tuples that we still need (because we think their parent tuples are
only RECENTLY_DEAD).  Per further thought about bug #5998.
This commit is contained in:
Tom Lane 2011-05-01 17:57:40 -04:00
parent 007a6e53ac
commit fb69fd176a
1 changed files with 17 additions and 0 deletions
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17
src/backend/commands/cluster.c
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@ -37,6 +37,7 @@
#include "commands/vacuum.h"
#include "miscadmin.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "storage/procarray.h"
#include "storage/smgr.h"
#include "utils/acl.h"
@ -781,6 +782,22 @@ copy_heap_data(Oid OIDNewHeap, Oid OIDOldHeap, Oid OIDOldIndex,
values = (Datum *) palloc(natts * sizeof(Datum));
isnull = (bool *) palloc(natts * sizeof(bool));
/*
* If the OldHeap has a toast table, get lock on the toast table to keep
* it from being vacuumed. This is needed because autovacuum processes
* toast tables independently of their main tables, with no lock on the
* latter. If an autovacuum were to start on the toast table after we
* compute our OldestXmin below, it would use a later OldestXmin, and then
* possibly remove as DEAD toast tuples belonging to main tuples we think
* are only RECENTLY_DEAD. Then we'd fail while trying to copy those
* tuples.
*
* We don't need to open the toast relation here, just lock it. The lock
* will be held till end of transaction.
*/
if (OldHeap->rd_rel->reltoastrelid)
LockRelationOid(OldHeap->rd_rel->reltoastrelid, AccessExclusiveLock);
/*
* We need to log the copied data in WAL iff WAL archiving/streaming is
* enabled AND it's not a temp rel.