From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
---|---|
To: | Bruce Momjian <bruce(at)momjian(dot)us> |
Cc: | Peter Geoghegan <pg(at)heroku(dot)com>, Robert Haas <robertmhaas(at)gmail(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: | 2014-01-28 17:47:08 |
Message-ID: | CA+U5nM+Vo9V24q_tM-ssgfSt3WAXr4cD8EdTM8dYkkNQa7sYTg@mail.gmail.com |
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Lists: | pgsql-hackers |
On 28 January 2014 17:15, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> On Tue, Jan 28, 2014 at 04:36:39PM +0000, Simon Riggs wrote:
>> For me, reducing the strength of DDL locking is a major change in
>> RDBMS behaviour that could both delight and surprise our users. Maybe
>> a few actually depend upon the locking behaviour, maybe. After some
>> years of various people looking at this, I think we've got it right.
>> Experience tells me that while I think this is the outcome, we are
>> well advised to protect against the possibility that it is not correct
>> and that if we have corner case issues, it would be good to easily
>> disable this in the field. In the current case, a simple parameter
>> works very well to disable the feature; in other cases, not.
>>
>> Summary: This is an atypical case. I do not normally propose such
>> things - this is the third time in 10 years, IIRC.
>
> Uh, in my memory, you are the person who is most likely to suggest a
> GUC of all our developers.
(smiles) I have suggested parameters for many features, mostly in the
early days of my developments before I saw the light if autotuning.
But those were control parameters for tuning features. So yes, I have
probably introduced more parameters than most, amongst the many things
I've done. I'm guessing you don't recall how much trouble I went to in
order to allow sync rep to have only 1 parameter, c'est la vie.
What I'm discussing here is a compatibility parameter to allow new
features to be disabled. This would be the third time in 10 years I
suggested a parameter for that reason, i.e. one that the user would
hardly ever wish to set.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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