Tom Lane wrote:
Heikki Linnakangas <[EMAIL PROTECTED]> writes:
It seems to me that we could easily reclaim a bit more dead tuples in a vacuum by recalculating the OldestXmin every now and then.


Doesn't this break relfrozenxid maintenance?

Not AFAICS. relfrozenxid is nowadays updated with FreezeLimit.

In any case I'd like to
see some evidence of significant real-world benefit before adding such
a conceptual wart ...

I've asked our testers to do a TPC-C run with and without the
patch. I'm not expecting it to make a huge difference there, but if you're using a big cost delay, it could make quite a difference for such a simple thing.

The procarray.c change scares me as well; I'm pretty sure the original
coding was intentional.

Well, it didn't make much difference before, since OldestXmin was always calculated early in the transaction.

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


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