Re: ERROR: missing chunk number 0 for toast value

From: Andres Freund <andres(at)2ndquadrant(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Rushabh Lathia <rushabh(dot)lathia(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Rushabh Lathia <rushabh(dot)lathia(at)enterprisedb(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Subject: Re: ERROR: missing chunk number 0 for toast value
Date: 2014-01-06 18:29:36
Message-ID: 20140106182936.GA22252@awork2.anarazel.de
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On 2014-01-06 12:40:25 -0500, Robert Haas wrote:
> On Mon, Jan 6, 2014 at 11:47 AM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> > On 2014-01-06 11:08:41 -0500, Robert Haas wrote:
> > Yea. But at least it would fail reliably instead of just under
> > concurrency and other strange circumstances - and there'd be a safe way
> > out. Currently there seem to be all sorts of odd behaviour possible.
> >
> > I simply don't have a better idea :(
>
> Is "forcibly detoast everything" a complete no-go? I realize there
> are performance concerns with that approach, but I'm not sure how
> realistic a worry it actually is.

The scenario I am primarily worried about is turning a record assignment
which previously took up to BLOCK_SIZE + slop amount of memory into
something taking up to a gigabyte. That's a pretty damn hefty
change.
And there's no good way of preventing it short of using a variable for
each actually desired column which imnsho isn't really a solution.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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