Fix order of arguments to SubTransSetParent().

tglsfdc · kelvich · commit 104636777c05 · 2017-11-09T00:46:08.000+03:00
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
@@ -2341,7 +2341,7 @@ 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
`@@ -2341,7 +2341,7 @@ ProcessTwoPhaseBuffer(TransactionId xid,`
`2341`	`2341`	`}`
`2342`	`2342`
`2343`	`2343`	`if (setParent)`
`2344`		`- SubTransSetParent(xid, subxid, overwriteOK);`
	`2344`	`+ SubTransSetParent(subxid, xid, overwriteOK);`
`2345`	`2345`	`}`
`2346`	`2346`
`2347`	`2347`	`return buf;`