Re: TOAST versus VACUUM, or "missing chunk number 0 for toast value" identified

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Andrew Hammond <andrew(dot)george(dot)hammond(at)gmail(dot)com>
Subject: Re: TOAST versus VACUUM, or "missing chunk number 0 for toast value" identified
Date: 2011-10-28 19:47:13
Message-ID: 1319831114-sup-3152@alvh.no-ip.org
Views: Raw Message | Whole Thread | Download mbox
Thread:
Lists: pgsql-hackers


Excerpts from Tom Lane's message of vie oct 28 15:37:43 -0300 2011:

> The main concern I had about detoast before caching is the risk of
> circularity, ie, needing detoastable cache entries in order to figure
> out how to detoast. But I think it's probably okay. The current list
> of catalogs with toast tables is
>
> pg_attrdef
> pg_constraint
> pg_database
> pg_db_role_setting
> pg_description
> pg_proc
> pg_rewrite
> pg_seclabel
> pg_shdescription
> pg_statistic
> pg_trigger
>
> Of these, only pg_proc is even conceivably consulted during a toast
> table fetch, and we can be sure that functions needed for such a fetch
> don't have toasted entries. But we will have to be very wary of any
> future proposal for adding a toast table to pg_class, pg_index, etc.

BTW we had previous discussions about dropping pg_database's toast
table. Maybe this is a good time to do it, even if there's no risk of
this bug (or the hypothetical circularity detoasting problem) showing up
there.

--
Álvaro Herrera <alvherre(at)commandprompt(dot)com>
The PostgreSQL Company - Command Prompt, Inc.
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

In response to

Responses

Browse pgsql-hackers by date

  From Date Subject
Next Message Alvaro Herrera 2011-10-28 19:48:22 Re: TOAST versus VACUUM, or "missing chunk number 0 for toast value" identified
Previous Message Robert Haas 2011-10-28 19:40:51 Re: fstat vs. lseek