public inbox for [email protected]  

help / color / mirror / Atom feed

From: Andres Freund <[email protected]>
To: Tom Lane <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Justin Pryzby <[email protected]>
Cc: Kyotaro Horiguchi <[email protected]>
Cc: Erik Rijkers <[email protected]>
Cc: Matthias van de Meent <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: TRAP: FailedAssertion("HaveRegisteredOrActiveSnapshot()", File: "toast_internals.c", Line: 670, PID: 19403)
Date: Thu, 14 Apr 2022 18:30:10 -0700
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <CA+TgmoZ1P5XxBvk1sU9s5hpHXAZf8u5oHTP1+h_otx2kHaG9QQ@mail.gmail.com>
	<[email protected]>
	<CA+TgmoagKyvcMip+thF8JS0Jc9kAnQnZS0xBpTetixRukdh=qg@mail.gmail.com>
	<[email protected]>
	<CA+TgmoaLb0j9zEfkk6bmuKM5422JenzzcJLJSiPLgwfMd+xnBw@mail.gmail.com>
	<[email protected]>
	<CA+TgmoYKWXhYRRSHwMTo-N48i64jOvq1yYmwrz7vHKFGnOyy8Q@mail.gmail.com>
	<[email protected]>
	<CA+Tgmob93_YftfhrSF+OpNWXWtv2bq774yBH3JxPiJf=-DxoiA@mail.gmail.com>
	<[email protected]>

Hi,

On 2022-04-14 15:05:50 -0400, Tom Lane wrote:
> Andres' complaint is that that snapshot might get invalidated when you
> weren't expecting it, but I'm not really convinced that we have all
> that many bugs of that ilk.  Wouldn't CLOBBER_CACHE_ALWAYS testing
> find them?

Don't see why it would - we don't have any mechanism in place for
enforcing that we don't update / delete a tuple we've looked up with an
xmin that wasn't continually enforced.  A typical pattern is to use a
catalog cache (registered an all) for a syscache lookup, but then not
have a registered / active snapshot until an eventual update / delete
(after the syscache scan ends). Which isn't safe, because without a
MyProc->xmin set, the tuple we're updating / deleting could be updated,
removed and replaced with another tuple.

Greetings,

Andres Freund

view thread (2+ messages)

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
  Subject: Re: TRAP: FailedAssertion("HaveRegisteredOrActiveSnapshot()", File: "toast_internals.c", Line: 670, PID: 19403)
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox