Re: TRAP: FailedAssertion("prev_first_lsn < cur_txn->first_lsn", File: "reorderbuffer.c", Line: 927, PID: 568639)

On Tue, Oct 18, 2022 at 7:56 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Mon, Oct 17, 2022 at 7:05 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >
> > On Thu, Oct 13, 2022 at 4:08 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > >
> > > --- a/src/backend/replication/logical/decode.c
> > > +++ b/src/backend/replication/logical/decode.c
> > > @@ -113,6 +113,15 @@
> > > LogicalDecodingProcessRecord(LogicalDecodingContext *ctx,
> > > XLogReaderState *recor
> > > buf.origptr);
> > > }
> > >
> > > +#ifdef USE_ASSERT_CHECKING
> > > + /*
> > > + * Check the order of transaction LSNs when we reached the start decoding
> > > + * LSN. See the comments in AssertTXNLsnOrder() for details.
> > > + */
> > > + if (SnapBuildGetStartDecodingAt(ctx->snapshot_builder) == buf.origptr)
> > > + AssertTXNLsnOrder(ctx->reorder);
> > > +#endif
> > > +
> > > rmgr = GetRmgr(XLogRecGetRmid(record));
> > > >
> > >
> > > I am not able to think how/when this check will be useful. Because we
> > > skipped assert checking only for records that are prior to
> > > start_decoding_at point, I think for those records ordering should
> > > have been checked before the restart. start_decoding_at point will be
> > > either (a) confirmed_flush location, or (b) lsn sent by client, and
> > > any record prior to that must have been processed before restart.
> >
> > Good point. I was considering the case where the client sets far ahead
> > LSN but it's not worth considering this case in this context. I've
> > updated the patch accoringly.
> >
>
> One minor comment:
> Can we slightly change the comment: ". The ordering of the records
> prior to the LSN, we should have been checked before the restart." to
> ". The ordering of the records prior to the start_decoding_at LSN
> should have been checked before the restart."?

Agreed. I'll update the patch accordingly.

Regards,

--
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com