| From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
| Cc: | "houzj(dot)fnst(at)fujitsu(dot)com" <houzj(dot)fnst(at)fujitsu(dot)com>, Peter Smith <smithpb2250(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Euler Taveira <euler(at)eulerto(dot)com>, "shiy(dot)fnst(at)fujitsu(dot)com" <shiy(dot)fnst(at)fujitsu(dot)com>, Greg Nancarrow <gregn4422(at)gmail(dot)com>, vignesh C <vignesh21(at)gmail(dot)com>, Ajin Cherian <itsajin(at)gmail(dot)com>, "tanghy(dot)fnst(at)fujitsu(dot)com" <tanghy(dot)fnst(at)fujitsu(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Rahila Syed <rahilasyed90(at)gmail(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, Önder Kalacı <onderkalaci(at)gmail(dot)com>, japin <japinli(at)hotmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, David Steele <david(at)pgmasters(dot)net>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Amit Langote <amitlangote09(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: row filtering for logical replication |
| Date: | 2022-04-12 11:54:50 |
| Message-ID: | CAA4eK1KdUDNgkXJbHUVBNaD6OWsrM_wDWb6o2RP7XYDuU3fGDA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Apr 12, 2022 at 5:01 PM Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
>
> On 2022-Apr-12, Amit Kapila wrote:
>
> > On Tue, Apr 12, 2022 at 3:45 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> > > We don't have a lock on the relation, so if it gets dropped
> > > concurrently, it won't behave sanely. For example, get_rel_name() will
> > > return NULL which seems incorrect to me.
>
> Oh, oops ... a trap for the unwary? Anyway, yes, we can disregard the
> entry when get_rel_name returns null. Amended patch attached.
>
> > > I am not sure about this as well because you will instead do a RELOID
> > > cache lookup even when there is no row filter or column list.
>
> I guess my assumption is that the pg_class cache is typically more
> populated than other relcaches, but that's unsubstantiated. I'm not
> sure if we have any way to tell which one is the more common case.
> Anyway, let's do it the way you already had it.
>
> > It seems to me that we have a similar coding pattern in ExecGrant_Relation().
>
> Not sure what you mean?
>
I mean that it fetches the tuple from the RELOID cache and then
performs relkind and other checks similar to what we are doing. I
think it could also have used get_rel_relkind() but probably not done
because it doesn't have a lock on the relation.
--
With Regards,
Amit Kapila.
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