Re: ALTER TABLE lock strength reduction patch is unsafe

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)2ndQuadrant(dot)com>, Peter Geoghegan <pg(at)heroku(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: ALTER TABLE lock strength reduction patch is unsafe
Date: 2014-03-03 15:53:20
Message-ID: 8223.1393862000@sss.pgh.pa.us
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Simon Riggs <simon(at)2ndQuadrant(dot)com> writes:
> On 3 March 2014 15:19, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> What I'm
>> really concerned about is whether there are other things like the
>> SnapshotNow issues that can cause stuff to halt and catch fire. I
>> don't know whether there are or are not, but that's my concern.

> Of course its a concern, I feel it also. But that's why we have beta
> period to handle the unknowns.

I have exactly zero faith that beta testing would catch low-probability
problems in this area. What's needed, and hasn't happened AFAIK, is
detailed study of the patch by assorted senior hackers.

> The question is are there any specific areas of concern here? If not,
> then we commit because we've done a lot of work on it and at the
> moment the balance is high benefit to users against a non-specific
> feeling of risk.

This is backwards. The default decision around here has never been
to commit when in doubt.

regards, tom lane

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