Re: ALTER TABLE lock strength reduction patch is unsafe

On 26 February 2014 15:25, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> On 2014-02-26 15:15:00 +0000, Simon Riggs wrote:
>> On 26 February 2014 13:38, Andres Freund <andres(at)2ndquadrant(dot)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.
>
> Yea, that's not what I am looking for.
>
>> 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?
>
> I think some isolationtester tests for the most important changes in
> lock levels are appropriate. Say, create a PRIMARY KEY, DROP INHERIT,
> ... while a query is in progress in a nother session.

OK, I'll work on some tests.

v18 attached, with v19 coming soon

--
Simon Riggs http://www.2ndQuadrant.com/
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