Re: row filtering for logical replication

On 2022-Jan-28, Andres Freund wrote:

> > +    foreach(lc, data->publications)
> > +    {
> > +        Publication *pub = lfirst(lc);

...

> Isn't this basically O(schemas * publications)?

Yeah, there are various places in the logical replication code that seem
pretty careless about this kind of thing -- most of it seems to assume
that there are going to be few publications, so it just looks things up
over and over with abandon, and I saw at least one place where it looped
up an inheritance hierarchy for partitioning doing indexscans at each
level(*).  I think a lot more thought is going to be required to fix
these things in a thorough manner -- a log.repl.-specific caching
mechanism, I imagine.

(*) Before 025b920a3d45, psql was forced to seqscan pg_publication_rel
for one of the describe.c queries, and nobody seems to have noticed.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
Y una voz del caos me habló y me dijo
"Sonríe y sé feliz, podría ser peor".
Y sonreí. Y fui feliz.
Y fue peor.