Re: Assigning fixed OIDs to system catalogs and indexes

"Qingqing Zhou" <zhouqq(at)cs(dot)toronto(dot)edu> writes:
> template1=# cluster pg_attribute_relid_attnam_index on pg_attribute;
> ERROR: "pg_attribute" is a system catalog

That error has nothing to do with any risk of reassigning OIDs. The
issue is whether we can change the index's relfilenode or not --- the
error is actually coming from here:

/*
* Disallow clustering system relations. This will definitely NOT
* work for shared relations (we have no way to update pg_class rows
* in other databases), nor for nailed-in-cache relations (the
* relfilenode values for those are hardwired, see relcache.c). It
* might work for other system relations, but I ain't gonna risk it.
*/
if (IsSystemRelation(OldHeap))
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("\"%s\" is a system catalog",
RelationGetRelationName(OldHeap))));

AFAIK it would work for cases not explained in the comment, but it's
not been tested.

regards, tom lane