On 8/21/06, Tom Lane <[EMAIL PROTECTED]> wrote:
"Marko Kreen" <[EMAIL PROTECTED]> writes:
> Dropping the pg_sync_txid() would be loss, because that means that
> user cannot just dump and restore the data and just continue where
> it left off.  Maybe its not a problem for replication but for generic
> queueing it would need delicate juggling when restoring backup.

I'm not following the point here.  Dump and restore has never intended
to preserve the transaction counter, so why should it preserve
high-order bits of the transaction counter?

Thus it guarantees that any new issued large txid's will be larger
than existing ones in tables.  Thus code can depend on monotonous

There is another problem with pg_sync_txid, too: because it is willing
to advance the extended XID counter in multiples of 4G XIDs, it turns
wraparound of the extended counter from a never-will-happen scenario
into something that could happen in a poorly-managed installation.
If you've got to be prepared to cope with wraparound of the extended
counter, then what the heck is the point at all?  You might as well just
work with XIDs as they stand.

Indeed.  I also don't like that scenario.

So I think pg_sync_txid is a bad idea.  In the patch as committed,
anyone who's really intent on munging the epoch can do it with
pg_resetxlog, but there's not a provision for doing it short of that.

I like it.  It is indeed better than having pg_dump issuing a function
call.  This fully satisfactory.


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