On Tue, Sep 15, 2020 at 2:04 PM Andres Freund wrote:
> > How is it possible? Because tuple which has a committed xmax and the
> > xmax is older than the oldestXmin, should not come for freezing unless
> > it is lock_only xid (because those tuples are already gone).
>
> There've been several cases
Hi,
On 2020-09-15 12:52:25 +0530, Dilip Kumar wrote:
> On Tue, Sep 15, 2020 at 11:14 AM Andres Freund wrote:
> >
> > On 2020-09-15 10:54:29 +0530, Dilip Kumar wrote:
> > > What problem do you see if we set xmax to the InvalidTransactionId and
> > > HEAP_XMAX_INVALID flag in the infomask ?
> >
> >
On Tue, Sep 15, 2020 at 11:14 AM Andres Freund wrote:
>
> On 2020-09-15 10:54:29 +0530, Dilip Kumar wrote:
> > What problem do you see if we set xmax to the InvalidTransactionId and
> > HEAP_XMAX_INVALID flag in the infomask ?
>
> 1) It'll make a dead tuple appear live. You cannot do this for tupl
On 2020-09-15 10:54:29 +0530, Dilip Kumar wrote:
> What problem do you see if we set xmax to the InvalidTransactionId and
> HEAP_XMAX_INVALID flag in the infomask ?
1) It'll make a dead tuple appear live. You cannot do this for tuples
with an xid below the horizon.
2) it'll break HOT chain foll
On Tue, Sep 15, 2020 at 2:35 AM Andres Freund wrote:
>
> Hi,
>
> On 2020-09-14 17:00:48 -0400, Robert Haas wrote:
> > On Mon, Sep 14, 2020 at 4:13 PM Andres Freund wrote:
> > > My understanding of the case we're discussing is that it's corruption
> > > (e.g. relfrozenxid being different than tabl
Hi,
On 2020-09-14 17:00:48 -0400, Robert Haas wrote:
> On Mon, Sep 14, 2020 at 4:13 PM Andres Freund wrote:
> > My understanding of the case we're discussing is that it's corruption
> > (e.g. relfrozenxid being different than table contents) affecting a HOT
> > chain. I.e. by definition all withi
On Mon, Sep 14, 2020 at 4:13 PM Andres Freund wrote:
> My understanding of the case we're discussing is that it's corruption
> (e.g. relfrozenxid being different than table contents) affecting a HOT
> chain. I.e. by definition all within a single page. We won't have
> modified part of it independ
Hi,
On 2020-09-14 15:50:49 -0400, Robert Haas wrote:
> On Mon, Sep 14, 2020 at 3:00 PM Alvaro Herrera
> wrote:
> > FWIW I agree with Andres' stance on this. The current system is *very*
> > complicated and bugs are obscure already. If we hide them, what we'll
> > be getting is a system where d
On Mon, Sep 14, 2020 at 3:00 PM Alvaro Herrera wrote:
> FWIW I agree with Andres' stance on this. The current system is *very*
> complicated and bugs are obscure already. If we hide them, what we'll
> be getting is a system where data can become corrupted for no apparent
> reason.
I think I mig
On 2020-Sep-14, Andres Freund wrote:
> It seems pretty dangerous to me. What exactly are you going to put into
> xmin/xmax here? And how would anything you put into the first tuple not
> break index lookups? There's no such thing as a frozen xmax (so far), so
> what are you going to put in there?
Hi,
On 2020-09-14 13:26:27 -0400, Robert Haas wrote:
> On Sat, Aug 29, 2020 at 4:36 AM Dilip Kumar wrote:
> > One example is, suppose during vacuum, there are 2 tuples in the hot
> > chain, and the xmin of the first tuple is corrupted (i.e. smaller
> > than relfrozenxid). And the xmax of this
On Sat, Aug 29, 2020 at 4:36 AM Dilip Kumar wrote:
> One example is, suppose during vacuum, there are 2 tuples in the hot
> chain, and the xmin of the first tuple is corrupted (i.e. smaller
> than relfrozenxid). And the xmax of this tuple (which is same as the
> xmin of the second tuple) is sma
On Sat, Aug 29, 2020 at 1:46 AM Robert Haas wrote:
>
> On Fri, Aug 28, 2020 at 1:29 PM Andres Freund wrote:
> > It can break HOT chains, plain ctid chains etc, for example. Which, if
> > earlier / follower tuples are removed can't be detected anymore at a
> > later time.
>
> I think I need a more
On Fri, Aug 28, 2020 at 9:49 PM Robert Haas wrote:
>
> On Tue, Jul 21, 2020 at 9:21 AM Dilip Kumar wrote:
> > In the previous version, the feature was enabled for cluster/vacuum
> > full command as well. in the attached patch I have enabled it only
> > if we are running vacuum command. It will
On Fri, Aug 28, 2020 at 1:29 PM Andres Freund wrote:
> It can break HOT chains, plain ctid chains etc, for example. Which, if
> earlier / follower tuples are removed can't be detected anymore at a
> later time.
I think I need a more specific example here to understand the problem.
If the xmax of
Hi,
On 2020-08-28 12:37:17 -0400, Robert Haas wrote:
> On Mon, Jul 20, 2020 at 4:30 PM Andres Freund wrote:
> > If we really were to do something like this the option would need to be
> > called vacuum_allow_making_corruption_worse or such. Its need to be
> > *exceedingly* clear that it will like
On Mon, Jul 20, 2020 at 4:30 PM Andres Freund wrote:
> If we really were to do something like this the option would need to be
> called vacuum_allow_making_corruption_worse or such. Its need to be
> *exceedingly* clear that it will likely lead to making everything much
> worse.
I don't really und
On Tue, Jul 21, 2020 at 9:21 AM Dilip Kumar wrote:
> In the previous version, the feature was enabled for cluster/vacuum
> full command as well. in the attached patch I have enabled it only
> if we are running vacuum command. It will not be enabled during a
> table rewrite. If we think that it
On Mon, Jul 20, 2020 at 4:30 PM Andres Freund wrote:
> I'm extremely doubtful this is a good idea. In all likelihood this will
> just exascerbate corruption.
>
> You cannot just stop freezing tuples, that'll lead to relfrozenxid
> getting *further* out of sync with the actual table contents. And y
On Tue, Jul 21, 2020 at 4:08 PM Dilip Kumar wrote:
>
> On Tue, Jul 21, 2020 at 11:00 AM Dilip Kumar wrote:
> >
> > On Tue, Jul 21, 2020 at 2:00 AM Andres Freund wrote:
> > >
> > > Hi,
> > >
> > > On 2020-07-17 16:16:23 +0530, Dilip Kumar wrote:
> > > > The attached patch allows the vacuum to con
On Tue, Jul 21, 2020 at 11:00 AM Dilip Kumar wrote:
>
> On Tue, Jul 21, 2020 at 2:00 AM Andres Freund wrote:
> >
> > Hi,
> >
> > On 2020-07-17 16:16:23 +0530, Dilip Kumar wrote:
> > > The attached patch allows the vacuum to continue by emitting WARNING
> > > for the corrupted tuple instead of imm
On Tue, Jul 21, 2020 at 2:00 AM Andres Freund wrote:
>
> Hi,
>
> On 2020-07-17 16:16:23 +0530, Dilip Kumar wrote:
> > The attached patch allows the vacuum to continue by emitting WARNING
> > for the corrupted tuple instead of immediately error out as discussed
> > at [1].
> >
> > Basically, it pro
On Mon, Jul 20, 2020 at 10:14 PM Alvaro Herrera
wrote:
>
> On 2020-Jul-20, Dilip Kumar wrote:
>
> > On Fri, Jul 17, 2020 at 4:16 PM Dilip Kumar wrote:
>
> > > So if the vacuum_tolerate_damage is set then in
> > > all the cases in heap_prepare_freeze_tuple where the corrupted xid is
> > > detected
> 21 июля 2020 г., в 00:36, Alvaro Herrera
> написал(а):
>
>
>> FWIW we coped with this by actively monitoring this kind of corruption
>> with this amcheck patch [0]. One can observe this lost page updates
>> cheaply in indexes and act on first sight of corruption: identify
>> source of the
Hi,
On 2020-07-17 16:16:23 +0530, Dilip Kumar wrote:
> The attached patch allows the vacuum to continue by emitting WARNING
> for the corrupted tuple instead of immediately error out as discussed
> at [1].
>
> Basically, it provides a new GUC called vacuum_tolerate_damage, to
> control whether to
On 2020-Jul-20, Andrey M. Borodin wrote:
> I think the point here is to actually move relfrozenxid back. But the
> mince can't be turned back. If CLOG is rotated - the table is
> corrupted beyond easy repair.
Oh, I see. Hmm. Well, if you discover relfrozenxid that's newer and
the pg_clog files
> 20 июля 2020 г., в 21:44, Alvaro Herrera
> написал(а):
>
>> I think we shall do that in some cases
>> but IMHO it's not a very good idea in all the cases. Basically, if
>> the xmin precedes the relfrozenxid then probably we should allow to
>> update the relfrozenxid whereas if the xmin pre
On 2020-Jul-20, Dilip Kumar wrote:
> On Fri, Jul 17, 2020 at 4:16 PM Dilip Kumar wrote:
> > So if the vacuum_tolerate_damage is set then in
> > all the cases in heap_prepare_freeze_tuple where the corrupted xid is
> > detected, it will emit a warning and return that nothing is changed in
> > the
On Sun, Jul 19, 2020 at 4:56 PM Andrey M. Borodin wrote:
>
> Hi Dilip!
>
>
> > 17 июля 2020 г., в 15:46, Dilip Kumar написал(а):
> >
> > The attached patch allows the vacuum to continue by emitting WARNING
> > for the corrupted tuple instead of immediately error out as discussed
> > at [1].
> >
>
On Fri, Jul 17, 2020 at 4:16 PM Dilip Kumar wrote:
>
> The attached patch allows the vacuum to continue by emitting WARNING
> for the corrupted tuple instead of immediately error out as discussed
> at [1].
>
> Basically, it provides a new GUC called vacuum_tolerate_damage, to
> control whether to
Hi Dilip!
> 17 июля 2020 г., в 15:46, Dilip Kumar написал(а):
>
> The attached patch allows the vacuum to continue by emitting WARNING
> for the corrupted tuple instead of immediately error out as discussed
> at [1].
>
> Basically, it provides a new GUC called vacuum_tolerate_damage, to
> cont
The attached patch allows the vacuum to continue by emitting WARNING
for the corrupted tuple instead of immediately error out as discussed
at [1].
Basically, it provides a new GUC called vacuum_tolerate_damage, to
control whether to continue the vacuum or to stop on the occurrence of
a corrupted t
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