| From: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Nikhil Sontakke <nikhils(at)2ndquadrant(dot)com>, David Steele <david(at)pgmasters(dot)net>, Andres Freund <andres(at)anarazel(dot)de>, Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Petr Jelinek <petr(dot)jelinek(at)2ndquadrant(dot)com>, Sokolov Yura <y(dot)sokolov(at)postgrespro(dot)ru>, Stas Kelvich <s(dot)kelvich(at)postgrespro(dot)ru>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] logical decoding of two-phase transactions |
| Date: | 2018-07-16 17:38:28 |
| Message-ID: | ad722d03-4468-b5f7-8c59-8ac79ff3c2d0@2ndquadrant.com |
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| Lists: | pgsql-hackers |
On 07/16/2018 07:21 PM, Tom Lane wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> I agree. As a general statement, I think the idea of trying to
>> prevent transactions from aborting is really scary. It's almost an
>> axiom of the system that we're always allowed to abort, and I think
>> there could be a lot of unintended and difficult-to-fix consequences
>> of undermining that guarantee. I think it will be very difficult to
>> create a sound system for delaying transactions, and I doubt very much
>> that the proposed system is sound.
>
> Ugh, is this patch really dependent on such a thing?
>
Unfortunately it does :-( Without it the decoding (or output plugins)
may see catalogs broken in various ways - the catalog records may get
vacuumed, HOT chains are broken, ... There were attempts to change that
part, but that seems an order of magnitude more invasive than this.
> TBH, I think the odds of making that work are indistinguishable from zero;
> and even if you managed to commit something that did work at the instant
> you committed it, the odds that it would stay working in the face of later
> system changes are exactly zero. I would reject this idea out of hand.
>
Why? How is this significantly different from other patches touching
ProcArray and related bits?
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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