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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: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>
Cc: Rahila Syed <rahilasyed90@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Tomas Vondra <tomas.vondra@enterprisedb.com>, Peter Smith <smithpb2250@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2021-12-16T17:54:59Z
Lists: pgsql-hackers 
On 2021-Dec-16, houzj.fnst@fujitsu.com wrote:

> The patch ensures all columns of RT are in column list when CREATE/ALTER
> publication, but it seems doesn't prevent user from changing the replica
> identity or dropping the index used in replica identity. Do we also need to
> check those cases ?

Yes, we do.  As it happens, I spent a couple of hours yesterday writing
code for that, at least partially.  I haven't yet checked what happens
with cases like REPLICA NOTHING, or REPLICA INDEX <xyz> and then
dropping that index.

My initial ideas were a bit wrong BTW: I thought we should check the
combination of column lists in all publications (a bitwise-OR of column
bitmaps, so to speak).  But conceptually that's wrong: we need to check
the column list of each publication individually instead.  Otherwise, if
you wanted to hide a column from some publication but that column was
part of the replica identity, there'd be no way to identify the tuple in
the replica.  (Or, if the pgouput code disobeys the column list and
sends the replica identity even if it's not in the column list, then
you'd be potentially publishing data that you wanted to hide.)

-- 
Álvaro Herrera           39°49'30"S 73°17'W  —  https://www.EnterpriseDB.com/

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