RE: [PoC] pg_upgrade: allow to upgrade publisher node

Dear Bharath,

While checking more, I found some problems your PoC.

1. rm_is_record_decodable() returns true when WAL records are decodable.
Based on that, should is_valid be false when the function is true?
E.g., XLOG_HEAP_INSERT is accepted in the PoC.
2. XLOG_CHECKPOINT_SHUTDOWN and XLOG_RUNNING_XACTS should return false because
these records may be generated during the upgrade but they are acceptable.
3. A bit operations are done for extracting a WAL type, but the mask is
different based on the rmgr. E.g., XLOG uses XLR_INFO_MASK, but XACT uses
XLOG_XACT_OPMASK.
4. There is a possibility that "XLOG_HEAP_INSERT | XLOG_HEAP_INIT_PAGE" is inserted,
but it is not handled.

Regarding the 2., maybe we should say "if the reorderbuffer is modified while decoding,
rm_is_record_decodable must return false" or something. If so, the return value
of XLOG_END_OF_RECOVERY and XLOG_HEAP2_NEW_CID should be also changed.

I attached the fix patch for above. How do you think?

Best Regards,
Hayato Kuroda
FUJITSU LIMITED