Fix order of arguments to SubTransSetParent().

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
index 49b6429218786a292baa7bf0827447934f2cde75..79b3957d08bb94c48f0a35389faaa8c352de5829 100644 (file)
--- 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;