v4-0001-Make-invalid-primary_slot_name-follow-standard-GU.patch

From 91be58df0eb116300e8f29f713ade4a9a7754274 Mon Sep 17 00:00:00 2001
From: Fujii Masao <fujii@postgresql.org>
Date: Fri, 3 Oct 2025 23:00:57 +0900
Subject: [PATCH v4] Make invalid primary_slot_name follow standard GUC error
 reporting.

Previously, if primary_slot_name was set to an invalid slot name and
the configuration file was reloaded, both the postmaster and all other
backend processes reported a WARNING. With many processes running,
this could produce a flood of duplicate messages. The problem was that
the GUC check hook for primary_slot_name reported errors at WARNING
level via ereport().

This commit changes the check hook to use GUC_check_errdetail() and
GUC_check_errhint() for error reporting. As with other GUC parameters,
this causes non-postmaster processes to log the message at DEBUG3,
so by default, only the postmaster's message appears in the log file.
---
 src/backend/access/transam/xlogrecovery.c | 13 +++-
 src/backend/replication/slot.c            | 72 +++++++++++++++--------
 src/include/replication/slot.h            |  3 +
 3 files changed, 64 insertions(+), 24 deletions(-)

diff --git a/src/backend/access/transam/xlogrecovery.c b/src/backend/access/transam/xlogrecovery.c
index 52ff4d119e6..3e3c4da01a2 100644
--- a/src/backend/access/transam/xlogrecovery.c
+++ b/src/backend/access/transam/xlogrecovery.c
@@ -4761,9 +4761,20 @@ RecoveryRequiresIntParameter(const char *param_name, int currValue, int minValue
 bool
 check_primary_slot_name(char **newval, void **extra, GucSource source)
 {
+	int			err_code;
+	char	   *err_msg = NULL;
+	char	   *err_hint = NULL;
+
 	if (*newval && strcmp(*newval, "") != 0 &&
-		!ReplicationSlotValidateName(*newval, false, WARNING))
+		!ReplicationSlotValidateNameInternal(*newval, false, &err_code,
+											 &err_msg, &err_hint))
+	{
+		GUC_check_errcode(err_code);
+		GUC_check_errdetail("%s", err_msg);
+		if (err_hint != NULL)
+			GUC_check_errhint("%s", err_hint);
 		return false;
+	}
 
 	return true;
 }
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index fd0fdb96d42..9e92a79f993 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -260,35 +260,66 @@ ReplicationSlotShmemExit(int code, Datum arg)
 /*
  * Check whether the passed slot name is valid and report errors at elevel.
  *
+ * See comments for ReplicationSlotValidateNameInternal().
+ */
+bool
+ReplicationSlotValidateName(const char *name, bool allow_reserved_name,
+							int elevel)
+{
+	int			err_code;
+	char	   *err_msg = NULL;
+	char	   *err_hint = NULL;
+
+	if (!ReplicationSlotValidateNameInternal(name, allow_reserved_name,
+											 &err_code, &err_msg, &err_hint))
+	{
+		ereport(elevel,
+				errcode(err_code),
+				errmsg_internal("%s", err_msg),
+				(err_hint != NULL) ? errhint_internal("%s", err_hint) : 0);
+
+		pfree(err_msg);
+		if (err_hint != NULL)
+			pfree(err_hint);
+		return false;
+	}
+
+	return true;
+}
+
+/*
+ * Check whether the passed slot name is valid.
+ *
  * An error will be reported for a reserved replication slot name if
  * allow_reserved_name is set to false.
  *
  * Slot names may consist out of [a-z0-9_]{1,NAMEDATALEN-1} which should allow
  * the name to be used as a directory name on every supported OS.
  *
- * Returns whether the directory name is valid or not if elevel < ERROR.
+ * Returns true if the slot name is valid. Otherwise, returns false and stores
+ * the error code, error message, and optional hint in err_code, err_msg, and
+ * err_hint, respectively. The caller is responsible for freeing err_msg and
+ * err_hint, which are palloc'd.
  */
 bool
-ReplicationSlotValidateName(const char *name, bool allow_reserved_name,
-							int elevel)
+ReplicationSlotValidateNameInternal(const char *name, bool allow_reserved_name,
+									int *err_code, char **err_msg, char **err_hint)
 {
 	const char *cp;
 
 	if (strlen(name) == 0)
 	{
-		ereport(elevel,
-				(errcode(ERRCODE_INVALID_NAME),
-				 errmsg("replication slot name \"%s\" is too short",
-						name)));
+		*err_code = ERRCODE_INVALID_NAME;
+		*err_msg = psprintf(_("replication slot name \"%s\" is too short"), name);
+		*err_hint = NULL;
 		return false;
 	}
 
 	if (strlen(name) >= NAMEDATALEN)
 	{
-		ereport(elevel,
-				(errcode(ERRCODE_NAME_TOO_LONG),
-				 errmsg("replication slot name \"%s\" is too long",
-						name)));
+		*err_code = ERRCODE_NAME_TOO_LONG;
+		*err_msg = psprintf(_("replication slot name \"%s\" is too long"), name);
+		*err_hint = NULL;
 		return false;
 	}
 
@@ -298,24 +329,19 @@ ReplicationSlotValidateName(const char *name, bool allow_reserved_name,
 			  || (*cp >= '0' && *cp <= '9')
 			  || (*cp == '_')))
 		{
-			ereport(elevel,
-					(errcode(ERRCODE_INVALID_NAME),
-					 errmsg("replication slot name \"%s\" contains invalid character",
-							name),
-					 errhint("Replication slot names may only contain lower case letters, numbers, and the underscore character.")));
+			*err_code = ERRCODE_INVALID_NAME;
+			*err_msg = psprintf(_("replication slot name \"%s\" contains invalid character"), name);
+			*err_hint = psprintf(_("Replication slot names may only contain lower case letters, numbers, and the underscore character."));
 			return false;
 		}
 	}
 
 	if (!allow_reserved_name && IsSlotForConflictCheck(name))
 	{
-		ereport(elevel,
-				errcode(ERRCODE_RESERVED_NAME),
-				errmsg("replication slot name \"%s\" is reserved",
-					   name),
-				errdetail("The name \"%s\" is reserved for the conflict detection slot.",
-						  CONFLICT_DETECTION_SLOT));
-
+		*err_code = ERRCODE_RESERVED_NAME;
+		*err_msg = psprintf(_("replication slot name \"%s\" is reserved"), name);
+		*err_hint = psprintf(_("The name \"%s\" is reserved for the conflict detection slot."),
+							 CONFLICT_DETECTION_SLOT);
 		return false;
 	}
 
diff --git a/src/include/replication/slot.h b/src/include/replication/slot.h
index fe62162cde3..09c69f83d57 100644
--- a/src/include/replication/slot.h
+++ b/src/include/replication/slot.h
@@ -321,6 +321,9 @@ extern void ReplicationSlotInitialize(void);
 extern bool ReplicationSlotValidateName(const char *name,
 										bool allow_reserved_name,
 										int elevel);
+extern bool ReplicationSlotValidateNameInternal(const char *name,
+												bool allow_reserved_name,
+												int *err_code, char **err_msg, char **err_hint);
 extern void ReplicationSlotReserveWal(void);
 extern void ReplicationSlotsComputeRequiredXmin(bool already_locked);
 extern void ReplicationSlotsComputeRequiredLSN(void);
-- 
2.50.1