Re: ALTER TABLE lock strength reduction patch is unsafe

On 26 February 2014 13:38, Andres Freund <andres@2ndquadrant.com> wrote:
> Hi,
>
> On 2014-02-26 07:32:45 +0000, Simon Riggs wrote:
>> > * This definitely should include isolationtester tests actually
>> >   performing concurrent ALTER TABLEs. All that's currently there is
>> >   tests that the locklevel isn't too high, but not that it actually works.
>>
>> There is no concurrent behaviour here, hence no code that would be
>> exercised by concurrent tests.
>
> Huh? There's most definitely new concurrent behaviour. Previously no
> other backends could have a relation open (and locked) while it got
> altered (which then sends out relcache invalidations). That's something
> that should be tested.

It has been. High volume concurrent testing has been performed, per
Tom's original discussion upthread, but that's not part of the test
suite.
For other tests I have no guide as to how to write a set of automated
regression tests. Anything could cause a failure, so I'd need to write
an infinite set of tests to prove there is no bug *somewhere*. How
many tests are required? 0, 1, 3, 30?

>> > * Why does ChangeOwner need AEL?
>>
>> Ownership affects privileges, which includes SELECTs, hence AEL.
>
> So?

That reply could be added to any post. Please explain your concern.

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