Re: ALTER TABLE lock strength reduction patch is unsafe

On 27 February 2014 08:48, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> 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

v19 complete apart from requested comment additions

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