0001-Print-prefix-and-logical-WAL-message-content-in-pg_w.patch

From 1547277944f7aceb1d5b0a3ae46ec2acf02f3b06 Mon Sep 17 00:00:00 2001
From: Ashutosh Bapat <ashutosh.bapat@2ndquadrant.com>
Date: Tue, 18 Aug 2020 11:05:29 +0530
Subject: [PATCH] Print prefix and logical WAL message content in pg_waldump

Print logical WAL message prefix which is a null terminated ASCII
string. Print the actual message as a space separated hex byte string
since it may contain binary data. This is useful for debugging purposes.

Ashutosh Bapat
---
 src/backend/access/rmgrdesc/logicalmsgdesc.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/backend/access/rmgrdesc/logicalmsgdesc.c b/src/backend/access/rmgrdesc/logicalmsgdesc.c
index bff298c928..fdd03362e7 100644
--- a/src/backend/access/rmgrdesc/logicalmsgdesc.c
+++ b/src/backend/access/rmgrdesc/logicalmsgdesc.c
@@ -24,10 +24,24 @@ logicalmsg_desc(StringInfo buf, XLogReaderState *record)
 	if (info == XLOG_LOGICAL_MESSAGE)
 	{
 		xl_logical_message *xlrec = (xl_logical_message *) rec;
+		/*
+		 * Per LogLogicalMessage() actual logical message follows a null-terminated prefix of length
+		 * prefix_size.
+		 */
+		char   *prefix = xlrec->message;
+		char   *message = xlrec->message + xlrec->prefix_size;
+		int		cnt;
+		char   *sep = "";
 
-		appendStringInfo(buf, "%s message size %zu bytes",
+		appendStringInfo(buf, "%s message size %zu bytes, prefix %s; mesage: ",
 						 xlrec->transactional ? "transactional" : "nontransactional",
-						 xlrec->message_size);
+						 xlrec->message_size, prefix);
+		/* Write actual message as a series of hex bytes. */
+		for (cnt = 0; cnt < xlrec->message_size; cnt++)
+		{
+			appendStringInfo(buf, "%s%02X", sep, (unsigned char)message[cnt]);
+			sep = " ";
+		}
 	}
 }
 
-- 
2.17.1