Re: row filtering for logical replication

Tomas Vondra <tomas.vondra@enterprisedb.com>

From: Tomas Vondra <tomas.vondra@enterprisedb.com>
To: Ajin Cherian <itsajin@gmail.com>, Euler Taveira <euler@eulerto.com>
Cc: Peter Smith <smithpb2250@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Rahila Syed <rahilasyed90@gmail.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, Önder Kalacı <onderkalaci@gmail.com>, japin <japinli@hotmail.com>, Michael Paquier <michael@paquier.xyz>, David Steele <david@pgmasters.net>, Craig Ringer <craig@2ndquadrant.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Amit Langote <amitlangote09@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2021-09-27T13:34:08Z
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. Release cache tuple when no longer needed

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

  3. Fix one of the tests introduced in commit 52e4f0cd47.

  4. Allow specifying row filters for logical replication of tables.

  5. Move scanint8() to numutils.c

  6. Replace Test::More plans with done_testing

  7. Reduce relcache access in WAL sender streaming logical changes

  8. Small cleanups related to PUBLICATION framework code

  9. Add a view to show the stats of subscription workers.

  10. Allow publishing the tables of schema.

  11. Doc: improve documentation of CREATE/ALTER SUBSCRIPTION.

  12. Add PublicationTable and PublicationRelInfo structs

  13. Remove unused argument "txn" in maybe_send_schema().

  14. Add prepare API support for streaming transactions in logical replication.

  15. Unify PostgresNode's new() and get_new_node() methods

  16. Use l*_node() family of functions where appropriate

  17. Add support for prepared transactions to built-in logical replication.

  18. Restore the portal-level snapshot after procedure COMMIT/ROLLBACK.

  19. Rename a parse node to be more general

  20. Remove unused column atttypmod from initial tablesync query

  21. SEARCH and CYCLE clauses

Hi,

I see no one responded to this important part of my review so far:

On 9/23/21 2:33 PM, Tomas Vondra wrote:
> 3) create_subscription.sgml
> 
>      <literal>WHERE</literal> clauses, rows must satisfy all expressions
>      to be copied. If the subscriber is a
> 
> I'm rather skeptical about the principle that all expressions have to 
> match - I'd have expected exactly the opposite behavior, actually.
> 
> I see a subscription as "a union of all publications". Imagine for 
> example you have a data set for all customers, and you create a 
> publication for different parts of the world, like
> 
>    CREATE PUBLICATION customers_france
>       FOR TABLE customers WHERE (country = 'France');
> 
>    CREATE PUBLICATION customers_germany
>       FOR TABLE customers WHERE (country = 'Germany');
> 
>    CREATE PUBLICATION customers_usa
>       FOR TABLE customers WHERE (country = 'USA');
> 
> and now you want to subscribe to multiple publications, because you want 
> to replicate data for multiple countries (e.g. you want EU countries). 
> But if you do
> 
>    CREATE SUBSCRIPTION customers_eu
>           PUBLICATION customers_france, customers_germany;
> 
> then you won't get anything, because each customer belongs to just a 
> single country. Yes, I could create multiple individual subscriptions, 
> one for each country, but that's inefficient and may have a different 
> set of issues (e.g. keeping them in sync when a customer moves between 
> countries).
> 
> I might have missed something, but I haven't found any explanation why 
> the requirement to satisfy all expressions is the right choice.
> 
> IMHO this should be 'satisfies at least one expression' i.e. we should 
> connect the expressions by OR, not AND.

Am I the only one finding the current behavior strange? What's the 
reasoning supporting the current approach?


regards

-- 
Tomas Vondra
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