Fix possible recovery trouble if TRUNCATE overlaps a checkpoint.

If TRUNCATE causes some buffers to be invalidated and thus the
checkpoint does not flush them, TRUNCATE must also ensure that the
corresponding files are truncated on disk. Otherwise, a replay
from the checkpoint might find that the buffers exist but have
the wrong contents, which may cause replay to fail.

Report by Teja Mupparti. Patch by Kyotaro Horiguchi, per a design
suggestion from Heikki Linnakangas, with some changes to the
comments by me. Review of this and a prior patch that approached
the issue differently by Heikki Linnakangas, Andres Freund, Álvaro
Herrera, Masahiko Sawada, and Tom Lane.

Discussion: http://postgr.es/m/BYAPR06MB6373BF50B469CA393C614257ABF00@BYAPR06MB6373.namprd06.prod.outlook.com

1 files changed, 19 insertions, 7 deletions

diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index d739812f230..134b63f28b8 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -433,7 +433,10 @@ ProcArrayEndTransaction(PGPROC *proc, TransactionId latestXid)
 		pgxact->xmin = InvalidTransactionId;
 		/* must be cleared with xid/xmin: */
 		pgxact->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
-		pgxact->delayChkpt = false; /* be sure this is cleared in abort */
+
+		/* be sure this is cleared in abort */
+		pgxact->delayChkpt = 0;
+
 		proc->recoveryConflictPending = false;
 
 		Assert(pgxact->nxids == 0);
@@ -455,7 +458,10 @@ ProcArrayEndTransactionInternal(PGPROC *proc, PGXACT *pgxact,
 	pgxact->xmin = InvalidTransactionId;
 	/* must be cleared with xid/xmin: */
 	pgxact->vacuumFlags &= ~PROC_VACUUM_STATE_MASK;
-	pgxact->delayChkpt = false; /* be sure this is cleared in abort */
+
+	/* be sure this is cleared in abort */
+	pgxact->delayChkpt = 0;
+
 	proc->recoveryConflictPending = false;
 
 	/* Clear the subtransaction-XID cache too while holding the lock */
@@ -2259,7 +2265,8 @@ GetOldestSafeDecodingTransactionId(bool catalogOnly)
  * delaying checkpoint because they have critical actions in progress.
  *
  * Constructs an array of VXIDs of transactions that are currently in commit
- * critical sections, as shown by having delayChkpt set in their PGXACT.
+ * critical sections, as shown by having specified delayChkpt bits set in their
+ * PGXACT.
  *
  * Returns a palloc'd array that should be freed by the caller.
  * *nvxids is the number of valid entries.
@@ -2273,13 +2280,15 @@ GetOldestSafeDecodingTransactionId(bool catalogOnly)
  * for clearing of delayChkpt to propagate is unimportant for correctness.
  */
 VirtualTransactionId *
-GetVirtualXIDsDelayingChkpt(int *nvxids)
+GetVirtualXIDsDelayingChkpt(int *nvxids, int type)
 {
 	VirtualTransactionId *vxids;
 	ProcArrayStruct *arrayP = procArray;
 	int			count = 0;
 	int			index;
 
+	Assert(type != 0);
+
 	/* allocate what's certainly enough result space */
 	vxids = (VirtualTransactionId *)
 		palloc(sizeof(VirtualTransactionId) * arrayP->maxProcs);
@@ -2292,7 +2301,7 @@ GetVirtualXIDsDelayingChkpt(int *nvxids)
 		volatile PGPROC *proc = &allProcs[pgprocno];
 		volatile PGXACT *pgxact = &allPgXact[pgprocno];
 
-		if (pgxact->delayChkpt)
+		if ((pgxact->delayChkpt & type) != 0)
 		{
 			VirtualTransactionId vxid;
 
@@ -2318,12 +2327,14 @@ GetVirtualXIDsDelayingChkpt(int *nvxids)
  * those numbers should be small enough for it not to be a problem.
  */
 bool
-HaveVirtualXIDsDelayingChkpt(VirtualTransactionId *vxids, int nvxids)
+HaveVirtualXIDsDelayingChkpt(VirtualTransactionId *vxids, int nvxids, int type)
 {
 	bool		result = false;
 	ProcArrayStruct *arrayP = procArray;
 	int			index;
 
+	Assert(type != 0);
+
 	LWLockAcquire(ProcArrayLock, LW_SHARED);
 
 	for (index = 0; index < arrayP->numProcs; index++)
@@ -2335,7 +2346,8 @@ HaveVirtualXIDsDelayingChkpt(VirtualTransactionId *vxids, int nvxids)
 
 		GET_VXID_FROM_PGPROC(vxid, *proc);
 
-		if (pgxact->delayChkpt && VirtualTransactionIdIsValid(vxid))
+		if ((pgxact->delayChkpt & type) != 0 &&
+			VirtualTransactionIdIsValid(vxid))
 		{
 			int			i;