Re: BUG #17855: Uninitialised memory used when the name type value processed in binary mode of Memoize

On Fri, 26 Apr 2024 at 03:50, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I do not like testing "atttypid == NAMEOID" one bit. As noted,
> that will fail on domains over name. It will also result in
> unnecessary work when reading non-btree indexes that contain
> name, since I don't think anything else has the same hack
> that btree name_ops does (grep for cstring in pg_opclass.dat).
> I think the correct thing is to see whether the index opclass
> for the column is btree name_ops. We don't seem to have an
> oid_symbol macro for that, but it shouldn't be hard to add,
> at least in HEAD.

On looking at the relcache code, I don't see anywhere that we store
the opclass Oid in RelationData. IndexSupportInitialize() only records
the opcfamily and opcintype. Assuming we can't add new fields to
RelationData in the backbranches, is there a reason why we can't check
for rd_opfamily of TEXT_BTREE_FAM_OID and rd_opcintype of NAMEOID?

I've attached an updated patch that does it that way and also did a
round of commenting the code.

David