Re: Incomplete freezing when truncating a relation during vacuum

On 11/27/13 01:21, Andres Freund wrote:
> On 2013-11-26 13:32:44 +0100, Andres Freund wrote:
>> This seems to be the case since
>> b4b6923e03f4d29636a94f6f4cc2f5cf6298b8c8. I suggest we go back to using
>> scan_all to determine whether we can set new_frozen_xid. That's a slight
>> pessimization when we scan a relation fully without explicitly scanning
>> it in its entirety, but given this isn't the first bug around
>> scanned_pages/rel_pages I'd rather go that way. The aforementioned
>> commit wasn't primarily concerned with that.
>> Alternatively we could just compute new_frozen_xid et al before the
>> lazy_truncate_heap.
>
> I've gone for the latter in this preliminary patch. Not increasing
> relfrozenxid after an initial data load seems like a bit of a shame.
>
> I wonder if we should just do scan_all || vacrelstats->scanned_pages <
> vacrelstats->rel_pages?

Hmm, you did (scan_all || vacrelstats->scanned_pages <
vacrelstats->rel_pages) for relminmxid, and just
(vacrelstats->scanned_pages < vacrelstats->rel_pages) for relfrozenxid.
That was probably not what you meant to do, the thing you did for
relfrozenxid looks good to me.

Does the attached look correct to you?

- Heikki