Fix order of arguments to SubTransSetParent().

tglsfdc · tglsfdc · commit 8565808733ec · 2017-04-23T13:10:57.000-04:00
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
@@ -1922,7 +1922,7 @@ StandbyRecoverPreparedTransactions(bool overwriteOK)
 				TransactionId subxid = subxids[i];
 
 				Assert(TransactionIdFollows(subxid, xid));
-				SubTransSetParent(xid, subxid, overwriteOK);
+				SubTransSetParent(subxid, xid, overwriteOK);
 			}
 		}
 	}

Original file line number	Diff line number	Diff line change
`@@ -1922,7 +1922,7 @@ StandbyRecoverPreparedTransactions(bool overwriteOK)`
`1922`	`1922`	`TransactionId subxid = subxids[i];`
`1923`	`1923`
`1924`	`1924`	`Assert(TransactionIdFollows(subxid, xid));`
`1925`		`- SubTransSetParent(xid, subxid, overwriteOK);`
	`1925`	`+ SubTransSetParent(subxid, xid, overwriteOK);`
`1926`	`1926`	`}`
`1927`	`1927`	`}`
`1928`	`1928`	`}`