Use XID passed down by the remote datanode, if its available, when

GetCurrentTransactionIdIfAny() is called.

The regular GetCurrentTransactionId() does the same, without actually storing
the XID in the transaction state. We don't store the XID when the connection is
from a datanode, to ensure that a duplicate XID is not stored. There are other
technique employed to ensure multiple backends can participate in the same
global transaction.

This bug was causing wrong results when a query needs datanode-datanode
connections and updates are made previously in the same transaction, via a
different connection

Per report by Arun Shaji

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index b20f9d7e75b053a242a64a7df33f5821d9dd3bd7..bfa2433dd05511a467b01a7a604e998133cc8792 100644 (file)
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -548,6 +548,14 @@ GetCurrentTransactionId(void)
 TransactionId
 GetCurrentTransactionIdIfAny(void)
 {
+#ifdef XCP
+       /*
+        * Return XID if its available from the remote node, without assigning to
+        * the transaction state
+        */
+       if (IsConnFromDatanode())
+               return GetNextTransactionId();
+#endif
        return CurrentTransactionState->transactionId;
 }