Re: [BUG] Logical replication failure "ERROR: could not map filenode "base/13237/442428" to relation OID" with catalog modifying txns

On Tue, Jul 12, 2022 at 7:59 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Tue, Jul 12, 2022 at 2:53 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >
> > On Tue, Jul 12, 2022 at 5:58 PM shiy(dot)fnst(at)fujitsu(dot)com
> > <shiy(dot)fnst(at)fujitsu(dot)com> wrote:
> > >
> > >
> > > It happened when executing the following code because it tried to free a NULL
> > > pointer (catchange_xip).
> > >
> > > /* be tidy */
> > > if (ondisk)
> > > pfree(ondisk);
> > > + if (catchange_xip)
> > > + pfree(catchange_xip);
> > > }
> > >
> > > It seems to be related to configure option. I could reproduce it when using
> > > `./configure --enable-debug`.
> > > But I couldn't reproduce with `./configure --enable-debug CFLAGS="-Og -ggdb"`.
> >
> > Hmm, I could not reproduce this problem even if I use ./configure
> > --enable-debug. And it's weird that we checked if catchange_xip is not
> > null but we did pfree for it:
> >
>
> Yeah, this looks weird to me as well but one difference in running
> tests could be the timing of WAL LOG for XLOG_RUNNING_XACTS. That may
> change the timing of SnapBuildSerialize. The other thing we can try is
> by checking the value of catchange_xcnt before pfree.

Yeah, we can try that.

While reading the code, I realized that we try to pfree both ondisk
and catchange_xip also when we jumped to 'out:':

out:
ReorderBufferSetRestartPoint(builder->reorder,
builder->last_serialized_snapshot);
/* be tidy */
if (ondisk)
pfree(ondisk);
if (catchange_xip)
pfree(catchange_xip);

But we use both ondisk and catchange_xip only if we didn't jump to
'out:'. If this problem is related to compiler optimization with
'goto' statement, moving them before 'out:' might be worth trying.

>
> BTW, I think ReorderBufferGetCatalogChangesXacts should have an Assert
> to ensure rb->catchange_ntxns and xcnt are equal. We can probably then
> avoid having xcnt_p as an out parameter as the caller can use
> rb->catchange_ntxns instead.
>

Agreed.

Regards,

--
Masahiko Sawada
EDB: https://www.enterprisedb.com/