[Bizgres-general] Another use case

[Mark Kirkwood]

Mark Kirkwood wrote:
>
> Hmm , Yeah - good scenario. We might be ok if it is only the 
> [Row]Exclusive locks on the target relation that I'm dropping - as there 
> will still be AccessShare ones on all the relations in the query - which 
> should prevent the DROP COLUMN or similar from beginning.
>
>   

Actually Gavin is correct, we have to be a bit more subtle than that - 
merely dropping the [Row]ExclusiveLock could leave the target relation 
without any lock at all. However, I think taking an AccessShareLock and 
*then* dropping the [Row]ExclusiveLock should work as intended.

A quick piece of hackery to test this idea seemed to leave locks as 
indicated. - we can no doubt discuss this sort of thing in more detail 
next week when I'm at Greenplum (assuming planes from here to US don't 
get grounded.... ).

Cheers

Mark