Re: Column Filtering in Logical Replication

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От Alvaro Herrera
Тема Re: Column Filtering in Logical Replication
Дата
Msg-id 202201120041.p24wvsfcsope@alvherre.pgsql
обсуждение исходный текст
Ответ на Re: Column Filtering in Logical Replication  (Alvaro Herrera <alvherre@alvh.no-ip.org>)
Ответы Re: Column Filtering in Logical Replication  (Peter Eisentraut <peter.eisentraut@enterprisedb.com>)
Re: Column Filtering in Logical Replication  (Peter Eisentraut <peter.eisentraut@enterprisedb.com>)
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On 2022-Jan-11, Alvaro Herrera wrote:

> On 2022-Jan-10, Alvaro Herrera wrote:
> 
> > Hmm.  So you're saying that we should only raise errors about the column
> > list if we are publishing UPDATE or DELETE, but otherwise let the
> > replica identity be anything.  OK, I'll see if I can come up with a
> > reasonable set of rules ...
> 
> This is an attempt to do it that way.  Now you can add a table to a
> publication without regards for how column filter compares to the
> replica identity, as long as the publication does not include updates
> and inserts.

I discovered a big hole in this, which is that ALTER PUBLICATION SET
(publish='insert,update') can add UPDATE publishing to a publication
that was only publishing INSERTs.  It's easy to implement a fix: in
AlterPublicationOptions, scan the list of tables and raise an error if
any of them has a column list that doesn't include all the columns in
the replica identity.

However, that proposal has an ugly flaw: there is no index on
pg_publication_rel.prpubid, which means that the only way to find the
relations we need to inspect is to seqscan pg_publication_rel.

Also, psql's query for \dRp+ uses a seqscan in pg_publication_rel.

Therefore, I propose to add an index on pg_publication_rel.prpubid.

-- 
Álvaro Herrera              Valdivia, Chile  —  https://www.EnterpriseDB.com/
"¿Qué importan los años?  Lo que realmente importa es comprobar que
a fin de cuentas la mejor edad de la vida es estar vivo"  (Mafalda)



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