ResetSystemCaches(was Re: [HACKERS] relation ### modified while in use)

[Hiroshi Inoue]

Hi RelationCacheInvalidate() is called from ResetSystemCaches() and calles RelationFlushRelation() for all relation descriptors except some nailed system relations. I'm wondering why nailed relations could be exceptions. Conversely why must RelationCacheInvalidate() call RelationFlushRelation() for other system relations ? Isn't it sufficient to call smgrclose() and replace rd_rel member of system relations by the latest ones instead of calling RelationFlushRelation() ? There's -O option of postmaster(postgres) which allows system table structure modification. I'm suspicious if it has been used properly before. Comments ? Regards. Hiroshi Inoue