From 6ff5aa129933fbde034c0d21c28cf05e052511f9 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Thu, 17 Nov 2022 18:56:11 +0100
Subject: [PATCH] Fix MERGE tuple count with DO NOTHING

Reporting tuples for which nothing is done is useless and goes against
the documented behavior, so don't do it.

Backpatch to 15.

Reported by: Luca Ferrari
Discussion: https://postgr.es/m/CAKoxK+42MmACUh6s8XzASQKizbzrtOGA6G1UjzCP75NcXHsiNw@mail.gmail.com
---
 src/backend/executor/nodeModifyTable.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 0f357f8221..b7ea953b55 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -2799,7 +2799,7 @@ lmerge_matched:
 		{
 			case TM_Ok:
 				/* all good; perform final actions */
-				if (canSetTag)
+				if (canSetTag && commandType != CMD_NOTHING)
 					(estate->es_processed)++;
 
 				break;