Re: [BUG]Update Toast data failure in logical replication

From: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Euler Taveira <euler(at)eulerto(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Petr Jelinek <petr(dot)jelinek(at)enterprisedb(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Kuntal Ghosh <kuntalghosh(dot)2007(at)gmail(dot)com>, "tanghy(dot)fnst(at)fujitsu(dot)com" <tanghy(dot)fnst(at)fujitsu(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [BUG]Update Toast data failure in logical replication
Date: 2022-02-08 09:51:19
Message-ID: CAA4eK1L56jqRj9k+O-3MWSp6_-BKEBVxTQOf+yqLFGdd0boP+g@mail.gmail.com
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On Tue, Feb 8, 2022 at 12:48 AM Andres Freund <andres(at)anarazel(dot)de> wrote:
>
> On 2022-02-07 08:44:00 +0530, Amit Kapila wrote:
> > Right, and it is getting changed. We are just printing the first 200
> > characters (by using SQL [1]) from the decoded tuple so what is shown
> > in the results is the initial 200 bytes.
>
> Ah, I knew I must have been missing something.
>
>
> > The complete decoded data after the patch is as follows:
>
> Hm. I think we should change the way the strings are shortened - otherwise we
> don't really verify much in that test. Perhaps we could just replace the long
> repetitive strings with something shorter in the output?
>
> E.g. using something like regexp_replace(data, '(1234567890|9876543210){200}', '\1{200}','g')
> inside the substr().
>

This sounds like a good idea. Shall we do this as part of this patch
itself or as a separate improvement?

> Wonder if we should deduplicate the number of different toasted strings in the
> file to something that'd allow us to have a single "redact_toast" function or
> such. There's too many different ones to have a reasonbly simple redaction
> function right now.
>

I think this is also worth trying.

> But that's perhaps better done separately.
>

+1.

--
With Regards,
Amit Kapila.

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