On 12.04.2011 19:42, jagan wrote:
  Where is the OID of tuple stored in a WAL record of a
  tuple? If not with xl_heap_header, where is it stored? Is it
  stored at all?

     >  It's stored in the "tuple data" portion.

Is the OID also recorded with xl_heap_delete record as well or just the 
xl_heaptid? From my reading of the code it is not recorded.

Correct, it's not.

In general, why is OID of a tuple relegated as just another tuple data, when it can 
replace xl_heaptid as a much more stable tuple identifier. I understand that by recording 
tuples in terms of xl_heaptid (i.e., page/offset) means that the db can recover quickly 
but isn't there some value to storing a much "higher level" information in the 
WAL logs? For example, tuple manipulations, if recorded in terms of manipulation on tuple 
oids, can support applications such as these:


Possibly. On the other hand, another common complaint is that PostgreSQL writes a lot of WAL, much more than other DBMSs. Adding more higher-level information to WAL records would make that issue even worse. At the moment we only include the minimum amount of information needed for recovery.

  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com

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