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

author Tom Lane <tgl@sss.pgh.pa.us>

Sun, 1 May 2011 21:57:40 +0000 (17:57 -0400)

committer Tom Lane <tgl@sss.pgh.pa.us>

Sun, 1 May 2011 21:57:40 +0000 (17:57 -0400)

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.

src/backend/commands/cluster.c patch | blob | blame | history

diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c

index 153ed9a516bd2441c76b74d85d5d04bd9ccf5af0..3bc663b0f3a76fd4bd11970120f406a3a6c105ac 100644 (file)

--- a/src/backend/commands/cluster.c

+++ b/src/backend/commands/cluster.c

@@ -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.

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