Horton

Re: logical decoding and replication of sequences, take 2

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Cc: Dilip Kumar <dilipbalaut@gmail.com>, Tomas Vondra <tomas.vondra@enterprisedb.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Masahiko Sawada <sawada.mshk@gmail.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Date: 2023-12-15T02:33:14Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Migrate logical slots to the new node during an upgrade.

  2. Make test_decoding ddl.out shorter

  3. Fix snapshot handling in logicalmsg_decode

  4. doc: Adjust a few more references to "postmaster"

  5. Revert "Logical decoding of sequences"

On Thu, Dec 14, 2023 at 9:14 PM Ashutosh Bapat
<ashutosh.bapat.oss@gmail.com> wrote:
>
> On Thu, Dec 14, 2023 at 2:51 PM Amit Kapila <amit.kapila16@gmail.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.