Horton

Re: row filtering for logical replication

Tomas Vondra <tomas.vondra@enterprisedb.com>

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From: Tomas Vondra <tomas.vondra@enterprisedb.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>, Dilip Kumar <dilipbalaut@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Euler Taveira <euler@eulerto.com>, Peter Smith <smithpb2250@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: 2021-07-14T14:16:56Z
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


On 7/14/21 4:01 PM, Alvaro Herrera wrote:
> On 2021-Jul-14, Dilip Kumar wrote:
> 
>> I think for insert we are only allowing those rows to replicate which
>> are matching filter conditions, so if we updating any row then also we
>> should maintain that sanity right? That means at least on the NEW rows
>> we should apply the filter, IMHO.  Said that, now if there is any row
>> inserted which were satisfying the filter and replicated, if we update
>> it with the new value which is not satisfying the filter then it will
>> not be replicated,  I think that makes sense because if an insert is
>> not sending any row to a replica which is not satisfying the filter
>> then why update has to do that, right?
> 
> Right, that's a good aspect to think about.
> 

I agree, that seems like a reasonable approach.

The way I'm thinking about this is that for INSERT and DELETE it's clear 
which row version should be used (because there's just one). And for 
UPDATE we could see that as DELETE + INSERT, and apply the same rule to 
each action.

On the other hand, I can imagine cases where it'd be useful to send the 
UPDATE when the old row matches the condition and new row does not.

> I think the guiding principle for which tuple to use for the filter is
> what is most useful to the potential user of the feature, rather than
> what is the easiest to implement.
> 

+1

-- 
Tomas Vondra
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