From 6578c8c390e245ece2d1305f3d2c78168a0e7d30 Mon Sep 17 00:00:00 2001
From: Zizhuan Liu <44973863@qq.com>
Date: Sat, 27 Jun 2026 10:04:15 +0800
Subject: [PATCH v2] If the domain is already in the target NULL or NOT NULL
 state, emit a safety notice and skip the add/set operation.

---
 src/backend/commands/typecmds.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/backend/commands/typecmds.c b/src/backend/commands/typecmds.c
index c4c3cdb5..7b8f9ed9 100644
--- a/src/backend/commands/typecmds.c
+++ b/src/backend/commands/typecmds.c
@@ -2799,6 +2799,10 @@ AlterDomainNotNull(List *names, bool notNull)
 	/* Is the domain already set to the desired constraint? */
 	if (typTup->typnotnull == notNull)
 	{
+		ereport(NOTICE,
+				(errmsg("Domain \"%s\" is already %s, skipping",
+						NameStr(typTup->typname), notNull ? "NOT NULL" : "NULL")));
+
 		table_close(typrel, RowExclusiveLock);
 		return address;
 	}
@@ -3033,6 +3037,10 @@ AlterDomainAddConstraint(List *names, Node *newConstraint,
 		/* Is the domain already set NOT NULL? */
 		if (typTup->typnotnull)
 		{
+			ereport(NOTICE,
+					(errmsg("Domain \"%s\" is already NOT NULL, skipping",
+							NameStr(typTup->typname))));
+
 			table_close(typrel, RowExclusiveLock);
 			return address;
 		}
-- 
2.43.0