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, 14 insertions, 2 deletions

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 6772e248222..51efc106a2c 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -9022,18 +9022,30 @@ CreateCheckPoint(int flags)
 	 * and we will correctly flush the update below.  So we cannot miss any
 	 * xacts we need to wait for.
 	 */
-	vxids = GetVirtualXIDsDelayingChkpt(&nvxids);
+	vxids = GetVirtualXIDsDelayingChkpt(&nvxids, DELAY_CHKPT_START);
 	if (nvxids > 0)
 	{
 		do
 		{
 			pg_usleep(10000L);	/* wait for 10 msec */
-		} while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids));
+		} while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids,
+											  DELAY_CHKPT_START));
 	}
 	pfree(vxids);
 
 	CheckPointGuts(checkPoint.redo, flags);
 
+	vxids = GetVirtualXIDsDelayingChkpt(&nvxids, DELAY_CHKPT_COMPLETE);
+	if (nvxids > 0)
+	{
+		do
+		{
+			pg_usleep(10000L);	/* wait for 10 msec */
+		} while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids,
+											  DELAY_CHKPT_COMPLETE));
+	}
+	pfree(vxids);
+
 	/*
 	 * Take a snapshot of running transactions and write this to WAL. This
 	 * allows us to reconstruct the state of running transactions during