Re: [HACKERS] WAL logging problem in 9.4.3?

Diffing the two latest versions of one patch:
> --- v32-0002-Fix-the-defect-1.patch    2020-01-18 14:32:47.499129940 -0800
> +++ v33-0002-Fix-the-defect-1.patch    2020-01-26 16:23:52.846391035 -0800
> +@@ -2978,8 +3054,8 @@ AssertPendingSyncs_RelationCache(void)
> +             LOCKTAG_RELATION)
> +             continue;
> +         relid = ObjectIdGetDatum(locallock->tag.lock.locktag_field2);
> +-        r = RelationIdGetRelation(relid);
> +-        if (r == NULL)
> ++        r = RelationIdGetRelationCache(relid);

The purpose of this loop is to create relcache entries for rels locked in the
current transaction.  (The "r == NULL" case happens for rels no longer visible
in catalogs.  It is harmless.)  Since RelationIdGetRelationCache() never
creates a relcache entry, calling it defeats that purpose.
RelationIdGetRelation() is the right function to call.

On Tue, Jan 21, 2020 at 06:45:57PM +0900, Kyotaro Horiguchi wrote:
> Three other fixes not mentined above are made. One is the useless
> rd_firstRelfilenodeSubid in the condition to dicide whether to
> preserve or not a relcache entry

It was not useless.  Test case:

  create table t (c int);
  begin;
  alter table t alter c type bigint;  -- sets rd_firstRelfilenodeSubid
  savepoint q; drop table t; rollback to q;  -- forgets rd_firstRelfilenodeSubid
  commit;  -- assertion failure, after s/RelationIdGetRelationCache/RelationIdGetRelation/ discussed above