Avoid sending prepare multiple times while decoding.

Amit Kapila · Amit Kapila · commit f25a4584c6f5 · 2021-04-26T11:27:44.000+05:30
We send the prepare for the concurrently aborted xacts so that later when rollback prepared is decoded and sent, the downstream should be able to rollback such a xact. For 'streaming' case (when we send changes for in-progress transactions), we were sending prepare twice when concurrent abort was detected. Author: Peter Smith Reviewed-by: Amit Kapila Discussion: https://postgr.es/m/f82133c6-6055-b400-7922-97dae9f2b50b@enterprisedb.com
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
@@ -2690,8 +2690,11 @@ ReorderBufferPrepare(ReorderBuffer *rb, TransactionId xid,
 	 * We send the prepare for the concurrently aborted xacts so that later
 	 * when rollback prepared is decoded and sent, the downstream should be
 	 * able to rollback such a xact. See comments atop DecodePrepare.
+	 *
+	 * Note, for the concurrent_abort + streaming case a stream_prepare was
+	 * already sent within the ReorderBufferReplay call above.
 	 */
-	if (txn->concurrent_abort)
+	if (txn->concurrent_abort && !rbtxn_is_streamed(txn))
 		rb->prepare(rb, txn, txn->final_lsn);
 }
 
