Re: Logical replication 'invalid memory alloc request size 1585837200' after upgrading to 17.5

On Thu, May 29, 2025 at 9:42 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Fri, May 30, 2025 at 9:31 AM vignesh C <vignesh21(at)gmail(dot)com> wrote:
> >
> > On Thu, 29 May 2025 at 22:57, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > >
> > > > I agree that chances are much lower than current if txn->invalidations
> > > > doesn't contain invalidations from other transactions, but it is not
> > > > clear what exactly you are trying to advocate by it. Are you trying to
> > > > advocate that we should maintain a member similar to txn->invalidation
> > > > (say txn->distributed_invals) instead of a queue?
> > >
> > > Yes, because I guess it's much simpler. I think it would not be a good
> > > idea to introduce a new concept of accounting the memory usage of the
> > > distributed inval messages too and serializing them, at least on back
> > > branches. I think that In case where the txn->distriubted_inval is
> > > about to overflow (not has to be 1GB) we can invalidate all caches
> > > instread.
> >
>
> I agree that it would be simpler, and to avoid invalid memory
> allocation requests even for rare cases, we can have the backup logic
> to invalidate all caches.
>
> > To identify overflow scenarios, I’m considering the following options:
> > a) Introduce a new txn_flags value, such as RBTXN_INVAL_ALL_CACHE, to
> > explicitly mark transactions that require full cache invalidation.
> > b) Add a dedicated parameter to indicate an overflow scenario.
> > c) setting the newly added nentries_distr to -1, to indicate an
> > overflow scenario.
> >
> > Do you have any preference or thoughts on which of these approaches
> > would be cleaner?
> >
>
> I would prefer (a) as that is an explicit way to indicate that we need
> to invalidate all caches. But let us see if Sawada-san has something
> else in mind.

(a) makes sense to me too. One concern in back branches is that unused
bits in txn_flags might be used by extensions, but it's unlikely.

Regards,

--
Masahiko Sawada
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