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Re: Column Filtering in Logical Replication

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Rahila Syed <rahilasyed90@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Tomas Vondra <tomas.vondra@enterprisedb.com>, Peter Smith <smithpb2250@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2021-12-10T20:02:08Z
Lists: pgsql-hackers 
On 2021-Sep-02, Alvaro Herrera wrote:

> On 2021-Sep-02, Rahila Syed wrote:
> 
> > After thinking about this, I think it is best to remove the entire table
> > from publication,
> > if a column specified in the column filter is dropped from the table.
> 
> Hmm, I think it would be cleanest to give responsibility to the user: if
> the column to be dropped is in the filter, then raise an error, aborting
> the drop.  Then it is up to them to figure out what to do.

I thought about this some more and realized that our earlier conclusions
were wrong or at least inconvenient.  I think that the best behavior if
you drop a column from a table is to remove the column from the
publication column list, and do nothing else.

Consider the case where you add a table to a publication without a
column filter, and later drop the column.  You don't get an error that
the relation is part of a publication; simply, the subscribers of that
publication will no longer receive that column.

Similarly for this case: if you add a table to a publication with a
column list, and later drop a column in that list, then you shouldn't
get an error either.  Simply the subscribers of that publication should
receive one column less.

Should be fairly quick to implement ... on it now.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"The problem with the facetime model is not just that it's demoralizing, but
that the people pretending to work interrupt the ones actually working."
                                                           (Paul Graham)

Commits

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

  1. Doc: Explain about Column List feature.

  2. Doc: fix column list vs. replica identity rules.

  3. Prohibit combining publications with different column lists.

  4. Fix the check to limit sync workers.

  5. Wait for subscription to sync in t/031_column_list.sql

  6. Move prattrs to the pg_publication_rel section in docs

  7. Allow specifying column lists for logical replication

  8. Fix row filters with multiple publications

  9. Fix publish_as_relid with multiple publications

  10. Add some additional tests for row filters in logical replication.

  11. Add index on pg_publication_rel.prpubid

  12. Avoid using DefElemAction in AlterPublicationStmt

  13. Small cleanups related to PUBLICATION framework code

  14. Add PublicationTable and PublicationRelInfo structs

  15. Fix various concurrency issues in logical replication worker launching