Remove the unnecessary PrepareWrite in pgoutput.

This issue exists from the inception of this code (PG-10) but got exposed
by the recent commit ce0fdbfe97 where we are using origins in tablesync
workers. The problem was that we were sometimes sending the prepare_write
('w') message but then the actual message was not being sent and on the
subscriber side, we always expect a message after prepare_write message
which led to this bug.

I refrained from backpatching this because there is no way in the core
code to hit this prior to commit ce0fdbfe97 and we haven't received any
complaints so far.

Reported-by: Erik Rijkers
Author: Amit Kapila and Vignesh C
Tested-by: Erik Rijkers
Discussion: https://postgr.es/m/[email protected]

1 files changed, 11 insertions, 8 deletions

diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
index 79765f96969..1b993fb032d 100644
--- a/src/backend/replication/pgoutput/pgoutput.c
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -342,10 +342,6 @@ pgoutput_begin_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn)
 	{
 		char	   *origin;
 
-		/* Message boundary */
-		OutputPluginWrite(ctx, false);
-		OutputPluginPrepareWrite(ctx, true);
-
 		/*----------
 		 * XXX: which behaviour do we want here?
 		 *
@@ -357,7 +353,13 @@ pgoutput_begin_txn(LogicalDecodingContext *ctx, ReorderBufferTXN *txn)
 		 *----------
 		 */
 		if (replorigin_by_oid(txn->origin_id, true, &origin))
+		{
+			/* Message boundary */
+			OutputPluginWrite(ctx, false);
+			OutputPluginPrepareWrite(ctx, true);
 			logicalrep_write_origin(ctx->out, origin, txn->origin_lsn);
+		}
+
 	}
 
 	OutputPluginWrite(ctx, true);
@@ -780,12 +782,13 @@ pgoutput_stream_start(struct LogicalDecodingContext *ctx,
 	{
 		char	   *origin;
 
-		/* Message boundary */
-		OutputPluginWrite(ctx, false);
-		OutputPluginPrepareWrite(ctx, true);
-
 		if (replorigin_by_oid(txn->origin_id, true, &origin))
+		{
+			/* Message boundary */
+			OutputPluginWrite(ctx, false);
+			OutputPluginPrepareWrite(ctx, true);
 			logicalrep_write_origin(ctx->out, origin, InvalidXLogRecPtr);
+		}
 	}
 
 	OutputPluginWrite(ctx, true);