Fix order of arguments to SubTransSetParent().

tglsfdc · tglsfdc · commit 0874d4f3e183 · 2017-04-23T13:11:06.000-04:00
ProcessTwoPhaseBuffer (formerly StandbyRecoverPreparedTransactions) mixed up the parent and child XIDs when calling SubTransSetParent to record the transactions' relationship in pg_subtrans. Remarkably, analysis by Simon Riggs suggests that this doesn't lead to visible problems (at least, not in non-Assert builds). That might explain why we'd not noticed it before. Nonetheless, it's surely wrong. This code was born broken, so back-patch to all supported branches. Discussion: https://postgr.es/m/20110.1492905318@sss.pgh.pa.us
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
@@ -2142,7 +2142,7 @@ ProcessTwoPhaseBuffer(TransactionId xid,
 		}
 
 		if (setParent)
-			SubTransSetParent(xid, subxid, overwriteOK);
+			SubTransSetParent(subxid, xid, overwriteOK);
 	}
 
 	return buf;

Original file line number	Diff line number	Diff line change
`@@ -2142,7 +2142,7 @@ ProcessTwoPhaseBuffer(TransactionId xid,`
`2142`	`2142`	`}`
`2143`	`2143`
`2144`	`2144`	`if (setParent)`
`2145`		`- SubTransSetParent(xid, subxid, overwriteOK);`
	`2145`	`+ SubTransSetParent(subxid, xid, overwriteOK);`
`2146`	`2146`	`}`
`2147`	`2147`
`2148`	`2148`	`return buf;`