Centralize some ALTER <whatever> .. SET SCHEMA checks.

Any flavor of ALTER <whatever> .. SET SCHEMA fails if (1) the object
is already in the new schema, (2) either the old or new schema is
a temp schema, or (3) either the old or new schema is the TOAST schema.

Extraced from a patch by Dimitri Fontaine, with additional hacking by me.

src/backend/catalog/dependency.c

@@ -2684,6 +2684,21 @@ getObjectDescription(const ObjectAddress *object)
 	return buffer.data;
 }
 
+/*
+ * getObjectDescriptionOids: as above, except the object is specified by Oids
+ */
+char *
+getObjectDescriptionOids(Oid classid, Oid objid)
+{
+	ObjectAddress	address;
+
+	address.classId = classid;
+	address.objectId = objid;
+	address.objectSubId = 0;
+
+	return getObjectDescription(&address);
+}
+
 /*
  * subroutine for getObjectDescription: describe a relation
  */

src/backend/catalog/namespace.c

@@ -2339,6 +2339,40 @@ LookupCreationNamespace(const char *nspname)
 	return namespaceId;
 }
 
+/*
+ * Common checks on switching namespaces.
+ *
+ * We complain if (1) the old and new namespaces are the same, (2) either the
+ * old or new namespaces is a temporary schema (or temporary toast schema), or
+ * (3) either the old or new namespaces is the TOAST schema.
+ */
+void
+CheckSetNamespace(Oid oldNspOid, Oid nspOid, Oid classid, Oid objid)
+{
+	if (oldNspOid == nspOid)
+		ereport(ERROR,
+				(classid == RelationRelationId ?
+					errcode(ERRCODE_DUPLICATE_TABLE) :
+				 classid == ProcedureRelationId ?
+					errcode(ERRCODE_DUPLICATE_FUNCTION) :
+					errcode(ERRCODE_DUPLICATE_OBJECT),
+				 errmsg("%s is already in schema \"%s\"",
+						getObjectDescriptionOids(classid, objid),
+						get_namespace_name(nspOid))));
+
+	/* disallow renaming into or out of temp schemas */
+	if (isAnyTempNamespace(nspOid) || isAnyTempNamespace(oldNspOid))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot move objects into or out of temporary schemas")));
+
+	/* same for TOAST schema */
+	if (nspOid == PG_TOAST_NAMESPACE || oldNspOid == PG_TOAST_NAMESPACE)
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot move objects into or out of TOAST schema")));
+}
+
 /*
  * QualifiedNameGetCreationNamespace
  *		Given a possibly-qualified name for an object (in List-of-Values

src/backend/commands/functioncmds.c

@@ -1899,24 +1899,8 @@ AlterFunctionNamespace(List *name, List *argtypes, bool isagg,
 	/* get schema OID and check its permissions */
 	nspOid = LookupCreationNamespace(newschema);
 
-	if (oldNspOid == nspOid)
-		ereport(ERROR,
-				(errcode(ERRCODE_DUPLICATE_FUNCTION),
-				 errmsg("function \"%s\" is already in schema \"%s\"",
-						NameListToString(name),
-						newschema)));
-
-	/* disallow renaming into or out of temp schemas */
-	if (isAnyTempNamespace(nspOid) || isAnyTempNamespace(oldNspOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-			errmsg("cannot move objects into or out of temporary schemas")));
-
-	/* same for TOAST schema */
-	if (nspOid == PG_TOAST_NAMESPACE || oldNspOid == PG_TOAST_NAMESPACE)
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("cannot move objects into or out of TOAST schema")));
+	/* common checks on switching namespaces */
+	CheckSetNamespace(oldNspOid, nspOid, ProcedureRelationId, procOid);
 
 	/* check for duplicate name (more friendly than unique-index failure) */
 	if (SearchSysCacheExists3(PROCNAMEARGSNSP,

src/backend/commands/tablecmds.c

@@ -8114,24 +8114,8 @@ AlterTableNamespace(RangeVar *relation, const char *newschema,
 	/* get schema OID and check its permissions */
 	nspOid = LookupCreationNamespace(newschema);
 
-	if (oldNspOid == nspOid)
-		ereport(ERROR,
-				(errcode(ERRCODE_DUPLICATE_TABLE),
-				 errmsg("relation \"%s\" is already in schema \"%s\"",
-						RelationGetRelationName(rel),
-						newschema)));
-
-	/* disallow renaming into or out of temp schemas */
-	if (isAnyTempNamespace(nspOid) || isAnyTempNamespace(oldNspOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-			errmsg("cannot move objects into or out of temporary schemas")));
-
-	/* same for TOAST schema */
-	if (nspOid == PG_TOAST_NAMESPACE || oldNspOid == PG_TOAST_NAMESPACE)
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("cannot move objects into or out of TOAST schema")));
+	/* common checks on switching namespaces */
+	CheckSetNamespace(oldNspOid, nspOid, RelationRelationId, relid);
 
 	/* OK, modify the pg_class row and pg_depend entry */
 	classRel = heap_open(RelationRelationId, RowExclusiveLock);

src/backend/commands/typecmds.c

@@ -2828,24 +2828,8 @@ AlterTypeNamespaceInternal(Oid typeOid, Oid nspOid,
 	oldNspOid = typform->typnamespace;
 	arrayOid = typform->typarray;
 
-	if (oldNspOid == nspOid)
-		ereport(ERROR,
-				(errcode(ERRCODE_DUPLICATE_OBJECT),
-				 errmsg("type %s is already in schema \"%s\"",
-						format_type_be(typeOid),
-						get_namespace_name(nspOid))));
-
-	/* disallow renaming into or out of temp schemas */
-	if (isAnyTempNamespace(nspOid) || isAnyTempNamespace(oldNspOid))
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-			errmsg("cannot move objects into or out of temporary schemas")));
-
-	/* same for TOAST schema */
-	if (nspOid == PG_TOAST_NAMESPACE || oldNspOid == PG_TOAST_NAMESPACE)
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("cannot move objects into or out of TOAST schema")));
+	/* common checks on switching namespaces */
+	CheckSetNamespace(oldNspOid, nspOid, TypeRelationId, typeOid);
 
 	/* check for duplicate name (more friendly than unique-index failure) */
 	if (SearchSysCacheExists2(TYPENAMENSP,

src/include/catalog/dependency.h

@@ -165,6 +165,7 @@ extern void recordDependencyOnSingleRelExpr(const ObjectAddress *depender,
 extern ObjectClass getObjectClass(const ObjectAddress *object);
 
 extern char *getObjectDescription(const ObjectAddress *object);
+extern char *getObjectDescriptionOids(Oid classid, Oid objid);
 
 extern ObjectAddresses *new_object_addresses(void);
 

src/include/catalog/namespace.h

@@ -94,6 +94,8 @@ extern Oid	LookupExplicitNamespace(const char *nspname);
 extern Oid	get_namespace_oid(const char *nspname, bool missing_ok);
 
 extern Oid	LookupCreationNamespace(const char *nspname);
+extern void CheckSetNamespace(Oid oldNspOid, Oid nspOid, Oid classid,
+							  Oid objid);
 extern Oid	QualifiedNameGetCreationNamespace(List *names, char **objname_p);
 extern RangeVar *makeRangeVarFromNameList(List *names);
 extern char *NameListToString(List *names);