Date: Thu, 22 Nov 2018 21:02:35 -0500
From: Stephen Frost <sfrost@snowman.net>
To: Euler Taveira <euler@timbira.com.br>
Cc: Craig Ringer <craig@2ndquadrant.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: row filtering for logical replication
Message-ID: <20181123020235.GG3415@tamriel.snowman.net>
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Greetings,

* Euler Taveira (euler@timbira.com.br) wrote:
> 2018-02-28 21:54 GMT-03:00 Craig Ringer <craig@2ndquadrant.com>:
> > Good idea. I haven't read this yet, but one thing to make sure you've
> > handled is limiting the clause to referencing only the current tuple and the
> > catalogs. user-catalog tables are OK, too, anything that is
> > RelationIsAccessibleInLogicalDecoding().
> >
> > This means only immutable functions may be invoked, since a stable or
> > volatile function might attempt to access a table. And views must be
> > prohibited or recursively checked. (We have tree walkers that would help
> > with this).
> >
> > It might be worth looking at the current logic for CHECK expressions, since
> > the requirements are similar. In my opinion you could safely not bother with
> > allowing access to user catalog tables in the filter expressions and limit
> > them strictly to immutable functions and the tuple its self.
>
> IIRC implementation is similar to RLS expressions. I'll check all of
> these rules.

Given the similarity to RLS and the nearby discussion about allowing
non-superusers to create subscriptions, and probably publications later,
I wonder if we shouldn't be somehow associating this with RLS policies
instead of having the publication filtering be entirely independent..

Thanks!

Stephen

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