Re: directory archive format for pg_dump - Mailing list pgsql-hackers

Heikki Linnakangas <heikki.linnakangas@enterprisedb.com> writes:
> On 16.12.2010 20:33, Joachim Wieland wrote:
>> How exactly would you "just split the table in chunks of roughly the
>> same size" ?

> Check pg_class.relpages, and divide that evenly across the processes. 
> That should be good enough.

Not even close ... relpages could be badly out of date.  If you believe
it, you could fail to dump data that's in further-out pages.  We'd need
to move pg_relpages() or some equivalent into core to make this
workable.

>> Which queries should pg_dump send to the backend?

> Hmm, I was thinking of "SELECT * FROM table WHERE ctid BETWEEN ? AND ?", 
> but we don't support TidScans for ranges. Perhaps we could add that.

Yeah, that seems probably workable, given an up-to-date idea of the
possible block range.
        regards, tom lane