Re: logical decoding and replication of sequences, take 2

On Thu, Dec 14, 2023 at 9:14 PM Ashutosh Bapat
<ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> wrote:
>
> On Thu, Dec 14, 2023 at 2:51 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > It can only be cleaned if we process it but xact_decode won't allow us
> > to process it and I don't think it would be a good idea to add another
> > hack for sequences here. See below code:
> >
> > xact_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
> > {
> > SnapBuild *builder = ctx->snapshot_builder;
> > ReorderBuffer *reorder = ctx->reorder;
> > XLogReaderState *r = buf->record;
> > uint8 info = XLogRecGetInfo(r) & XLOG_XACT_OPMASK;
> >
> > /*
> > * If the snapshot isn't yet fully built, we cannot decode anything, so
> > * bail out.
> > */
> > if (SnapBuildCurrentState(builder) < SNAPBUILD_FULL_SNAPSHOT)
> > return;
>
> That may be true for a transaction which is decoded, but I think all
> the transactions which are added to ReorderBuffer should be cleaned up
> once they have been processed irrespective of whether they are
> decoded/sent downstream or not. In this case I see the sequence hash
> being cleaned up for the sequence related transaction in Hayato's
> reproducer.
>

It was because the test you are using was not designed to show the
problem I mentioned. In this case, the rollback was after a full
snapshot state was reached.

--
With Regards,
Amit Kapila.