Re: ALTER command reworks - Mailing list pgsql-hackers

From Dimitri Fontaine
Subject Re: ALTER command reworks
Date
Msg-id m24nklvbyo.fsf@2ndQuadrant.fr
Whole thread Raw
In response to Re: ALTER command reworks  (Kohei KaiGai <kaigai@kaigai.gr.jp>)
Responses Re: ALTER command reworks  (Kohei KaiGai <kaigai@kaigai.gr.jp>)
List pgsql-hackers
Kohei KaiGai <kaigai@kaigai.gr.jp> writes:
> OK, Are you suggesting to add a "generic" comments such as "Generic
> function to change the name of a given object, for simple cases ...",
> not a list of OBJECT_* at the head of this function, aren't you?

Just something like
* Most simple objects are covered by a generic function, the other* still need special processing.

Mainly I was surprised to see collation not supported here, but I didn't
take enough time to understand why that is the case. I will do that
later in the review process.

> The pain point is AlterObjectNamespace_internal is not invoked by
> only ExecAlterObjectSchemaStmt(), but AlterObjectNamespace_oid()
> also.

I should remember better about that as the use case is extensions…

> It is the reason why I had to put get_object_type() to find out OBJECT_*
> from the supplied ObjectAddress, because this code path does not
> available to pass down its ObjectType from the caller.

If we really want to do that, I think I would only do that in
AlterObjectNamespace_oid and add an argument to
AlterObjectNamespace_internal, that you already have in
ExecAlterObjectSchemaStmt().

But really, what about just removing that part of your patch instead:

@@ -396,14 +614,23 @@ AlterObjectNamespace_internal(Relation rel, Oid objid, Oid nspOid)     * Check for duplicate name
(morefriendly than unique-index failure).     * Since this is just a friendliness check, we can just skip it in cases
 * where there isn't a suitable syscache available. 
+     *
+     * XXX - the caller should check object-name duplication, if the supplied
+     * object type need to take object arguments for identification, such as
+     * functions.     */
-    if (nameCacheId >= 0 &&
-        SearchSysCacheExists2(nameCacheId, name, ObjectIdGetDatum(nspOid)))
-        ereport(ERROR,
-                (errcode(ERRCODE_DUPLICATE_OBJECT),
-                 errmsg("%s already exists in schema \"%s\"",
-                        getObjectDescriptionOids(classId, objid),
-                        get_namespace_name(nspOid))));
+    if (get_object_catcache_name(classId) >= 0)
+    {
+        ObjectAddress    address;
+
+        address.classId = classId;
+        address.objectId = objid;
+        address.objectSubId = 0;
+
+        objtype = get_object_type(&address);
+        check_duplicate_objectname(objtype, nspOid,
+                                   NameStr(*DatumGetName(name)), NIL);
+    }

It would be much simpler to retain the old-style duplicate object check,
and compared to doing extra cache lookups, it'd still be much cleaner in
my view.

Regards,
--
Dimitri Fontaine
http://2ndQuadrant.fr     PostgreSQL : Expertise, Formation et Support



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