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* freeze cannot be finished
@ 2013-11-16 20:05 Миша Тюрин <tmihail@bk.ru>
0 siblings, 1 reply; 2+ messages in thread
From: Миша Тюрин @ 2013-11-16 20:05 UTC (permalink / raw)
To: pgsql-hackers; +Cc: Sergey Burladyan <eshkinkot@gmail.com>
Hello!
Could anyone review patch suggested by Jeff Janes ?
Initial thread http://www.postgresql.org/message-id/flat/1384356585.995240612@f50.i.mail.ru#1384356585.995240612@f5...
Thanks in advance!
>
> On Wed, Nov 13, 2013 at 3:53 PM, Sergey Burladyan < eshkinkot@gmail.com > wrote:
> >Jeff Janes < jeff.janes@gmail.com > writes:
> >
> >If I not mistaken, looks like lazy_scan_heap() called from lazy_vacuum_rel()
> >(see [1]) skip pages, even if it run with scan_all == true, lazy_scan_heap()
> >does not increment scanned_pages if lazy_check_needs_freeze() return false, so
> >if this occurred at wraparound vacuum it cannot update pg_class, because
> >pg_class updated via this code:
> >
> > new_frozen_xid = FreezeLimit;
> > if (vacrelstats->scanned_pages < vacrelstats->rel_pages)
> > new_frozen_xid = InvalidTransactionId;
> >
> > vac_update_relstats(onerel,
> > new_rel_pages,
> > new_rel_tuples,
> > new_rel_allvisible,
> > vacrelstats->hasindex,
> > new_frozen_xid);
> >
> >so i think in our prevent wraparound vacuum vacrelstats->scanned_pages always
> >less than vacrelstats->rel_pages and pg_class relfrozenxid never updated.
>
> Yeah, I think that that is a bug. If the clean-up lock is unavailable but the page is inspected without it and found not to need freezing, then the page needs to be counted as scanned, but is not so counted.
>
> commit bbb6e559c4ea0fb4c346beda76736451dc24eb4e
> Date: Mon Nov 7 21:39:40 2011 -0500
>
> But this was introduced in 9.2.0, so unless the OP didn't upgrade to 9.2 until recently, I don't know why it just started happening.
>
> It looks like a simple fix (to HEAD attached), but I don't know how to test it.
>
> Also, it seem like it might be worth issuing a warning if scan_all is true but all was not scanned.
>
> Cheers,
>
> Jeff
>
> --
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Attachments:
fix_freeze.patch (application/x-patch, 478B) download
diff --git a/src/backend/commands/vacuumlazy.c b/src/backend/commands/vacuumlazy.c
new file mode 100644
index e1d6d1c..6778c7d
*** a/src/backend/commands/vacuumlazy.c
--- b/src/backend/commands/vacuumlazy.c
*************** lazy_scan_heap(Relation onerel, LVRelSta
*** 602,607 ****
--- 602,608 ----
if (!lazy_check_needs_freeze(buf))
{
UnlockReleaseBuffer(buf);
+ vacrelstats->scanned_pages++;
continue;
}
LockBuffer(buf, BUFFER_LOCK_UNLOCK);
* Re: freeze cannot be finished
@ 2013-11-18 08:32 Heikki Linnakangas <hlinnakangas@vmware.com>
parent: Миша Тюрин <tmihail@bk.ru>
0 siblings, 0 replies; 2+ messages in thread
From: Heikki Linnakangas @ 2013-11-18 08:32 UTC (permalink / raw)
To: Миша Тюрин <tmihail@bk.ru>; +Cc: pgsql-hackers; Sergey Burladyan <eshkinkot@gmail.com>
Committed, thanks for the report!
On 16.11.2013 22:05, Миша Тюрин wrote:
> Hello!
>
> Could anyone review patch suggested by Jeff Janes ?
>
> Initial thread http://www.postgresql.org/message-id/flat/1384356585.995240612%40f50.i.mail.ru
>
> Thanks in advance!
>
>>
>> On Wed, Nov 13, 2013 at 3:53 PM, Sergey Burladyan < eshkinkot@gmail.com > wrote:
>>> Jeff Janes < jeff.janes@gmail.com > writes:
>>>
>>> If I not mistaken, looks like lazy_scan_heap() called from lazy_vacuum_rel()
>>> (see [1]) skip pages, even if it run with scan_all == true, lazy_scan_heap()
>>> does not increment scanned_pages if lazy_check_needs_freeze() return false, so
>>> if this occurred at wraparound vacuum it cannot update pg_class, because
>>> pg_class updated via this code:
>>>
>>> new_frozen_xid = FreezeLimit;
>>> if (vacrelstats->scanned_pages < vacrelstats->rel_pages)
>>> new_frozen_xid = InvalidTransactionId;
>>>
>>> vac_update_relstats(onerel,
>>> new_rel_pages,
>>> new_rel_tuples,
>>> new_rel_allvisible,
>>> vacrelstats->hasindex,
>>> new_frozen_xid);
>>>
>>> so i think in our prevent wraparound vacuum vacrelstats->scanned_pages always
>>> less than vacrelstats->rel_pages and pg_class relfrozenxid never updated.
>>
>> Yeah, I think that that is a bug. If the clean-up lock is unavailable but the page is inspected without it and found not to need freezing, then the page needs to be counted as scanned, but is not so counted.
>>
>> commit bbb6e559c4ea0fb4c346beda76736451dc24eb4e
>> Date: Mon Nov 7 21:39:40 2011 -0500
>>
>> But this was introduced in 9.2.0, so unless the OP didn't upgrade to 9.2 until recently, I don't know why it just started happening.
>>
>> It looks like a simple fix (to HEAD attached), but I don't know how to test it.
>>
>> Also, it seem like it might be worth issuing a warning if scan_all is true but all was not scanned.
>>
>> Cheers,
>>
>> Jeff
>>
>> --
>> Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
>> To make changes to your subscription:
>> https://urldefense.proofpoint.com/v1/url?u=http://www.postgresql.org/mailpref/pgsql-general&k=oI...
>
>>
>
> --
>
>
>
>
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2013-11-16 20:05 freeze cannot be finished Миша Тюрин <tmihail@bk.ru>
2013-11-18 08:32 ` Heikki Linnakangas <hlinnakangas@vmware.com>
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