Re: "Missing" column in Postgres logical replication update message

On 8/3/22 08:09, Kevin Martin wrote:

Please reply to list also
Ccing list

I don't have answers to below at the moment, just getting thread back to
list so others who might have answers can see it.

> Thanks for the reply, Adrian.
>
> We're looking at the messages in the replication slot using
> pg_logical_slot_peek_changes in the source db.
>
> In those messages, we see some UPDATEs that do not include one of the
> columns in the table.
>
> I'm not sure what statements are producing the updates to the table
> from the application, if that is what you are asking.  Does the update
> against the database have to include all columns in order for the
> replication log to have them all?
>
> I thought that any UPDATE message in the replication logs is designed to
> include all values for all columns.  Is that correct?
>
> The data is not showing up in the replica table.  In this case, though,
> the replication slot is being queried by Stitch to produce a copy in
> Snowflake.  That is probably somewhat irrelevant to the current
> question, though, since we appear to be seeing missing data in the
> replication slot messages on the source.
>
> I'm on the receiving side of this issue and am working with my DBA on
> trying to figure it out, so I'm not fully versed in how all of this
> works.  I can try to get more information if it helps.  I have seen the
> output from the peek function, and there are clearly some UPDATE
> messages that have the column / values in question and some that do not.
>
> On Wed, Aug 3, 2022 at 10:47 AM Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com
> <mailto:adrian(dot)klaver(at)aklaver(dot)com>> wrote:
>
> On 8/3/22 06:50, Kevin Martin wrote:
> > We have a replication slot set up on a database in Postgres 12.8.
> For
> > one of the tables, when a row is created, we see a series of records
> > come through - an INSERT followed by a handful of UPDATEs. All of
> these
> > messages in the WAL files show all columns, except for the last
> UPDATE
> > message, which is missing one of the columns. (The column in
> question is
> > a JSONB field, and the data is not overly large - less than 1000
> > chars.)  We think this is causing the data to come into our data
> lake
> > (via Stitch) with that column as NULL.
>
> See the messages where and/or how?
>
> What is the UPDATE command that is being given on primary?
>
> Is the data showing up in the replica table?
>
> >
> > My understanding is that all INSERT and UPDATE messages written
> to the
> > replication logs are supposed to include all columns. But I can't
> find a
> > definitive answer on that.
> >
> > So, my first question is: Is it normal / expected for UPDATE
> messages in
> > the replication logs to exclude any columns in the table?
> >
> > And, of course, if that is unexpected behavior, I'd love to hear any
> > thoughts on what may cause it.
> >
> > Thanks.
> >
> > -Kevin
> >
> >
> > FYI.  I have this question posted also on StackOverflow:
> >
> https://stackoverflow.com/questions/73222107/missing-column-in-postgres-logical-replication-update-message
> <https://stackoverflow.com/questions/73222107/missing-column-in-postgres-logical-replication-update-message>
>
> >
> <https://stackoverflow.com/questions/73222107/missing-column-in-postgres-logical-replication-update-message
> <https://stackoverflow.com/questions/73222107/missing-column-in-postgres-logical-replication-update-message>>
> >
>
>
> --
> Adrian Klaver
> adrian(dot)klaver(at)aklaver(dot)com <mailto:adrian(dot)klaver(at)aklaver(dot)com>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com