Exit correctly from PrepareRedoRemove() when not found

simonat2ndQuadrant · kelvich · commit e1b13ccbed2f · 2017-11-09T00:43:59.000+03:00
Complex crash bug all started with this failure. Diagnosed and fixed by Nikhil Sontakke, reviewed by me. Reported-by: Jeff Janes Author: Nikhil Sontakke Discussion: https://postgr.es/m/CAMkU=1xBP8cqdS5eK8APHL=X6RHMMM2vG5g+QamduuTsyCwv9g@mail.gmail.com
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
@@ -2633,6 +2633,7 @@ PrepareRedoRemove(TransactionId xid, bool giveWarning)
 {
 	GlobalTransaction gxact = NULL;
 	int			i;
+	bool		found = false;
 
 	Assert(LWLockHeldByMeInMode(TwoPhaseStateLock, LW_EXCLUSIVE));
 	Assert(RecoveryInProgress());
@@ -2644,14 +2645,15 @@ PrepareRedoRemove(TransactionId xid, bool giveWarning)
 		if (gxact->xid == xid)
 		{
 			Assert(gxact->inredo);
+			found = true;
 			break;
 		}
 	}
 
 	/*
 	 * Just leave if there is nothing, this is expected during WAL replay.
 	 */
-	if (gxact == NULL)
+	if (!found)
 		return;
 
 	/*

Original file line number	Diff line number	Diff line change
`@@ -2633,6 +2633,7 @@ PrepareRedoRemove(TransactionId xid, bool giveWarning)`
`2633`	`2633`	`{`
`2634`	`2634`	`GlobalTransaction gxact = NULL;`
`2635`	`2635`	`int i;`
	`2636`	`+ bool found = false;`
`2636`	`2637`
`2637`	`2638`	`Assert(LWLockHeldByMeInMode(TwoPhaseStateLock, LW_EXCLUSIVE));`
`2638`	`2639`	`Assert(RecoveryInProgress());`
`@@ -2644,14 +2645,15 @@ PrepareRedoRemove(TransactionId xid, bool giveWarning)`
`2644`	`2645`	`if (gxact->xid == xid)`
`2645`	`2646`	`{`
`2646`	`2647`	`Assert(gxact->inredo);`
	`2648`	`+ found = true;`
`2647`	`2649`	`break;`
`2648`	`2650`	`}`
`2649`	`2651`	`}`
`2650`	`2652`
`2651`	`2653`	`/*`
`2652`	`2654`	`* Just leave if there is nothing, this is expected during WAL replay.`
`2653`	`2655`	`*/`
`2654`		`- if (gxact == NULL)`
	`2656`	`+ if (!found)`
`2655`	`2657`	`return;`
`2656`	`2658`
`2657`	`2659`	`/*`