Re: pg_restore dependencies

Josh Berkus wrote:
> Tom,  Andrew,
>
>>> Well, we certainly want to be able to run CREATE INDEXes in parallel,
>>> so this would appear to require hard-wiring some conception of shared
>>> versus exclusive lock into pg_restore. I think it might be a bit late
>>> to consider that for 8.4.
>>
>>
>> I'm pretty sure I had the logic for this correct stuff originally, so
>> I'm going to go back and check that.
>
> FWIW, I've tested 3 moderately complex databases with this, and the 
> locking issue happens on every one.  As a result, getting more than 3 
> cores of scalability on any fairly complex DB isn't possible without 
> fixing this.


Yeah. I think the correct logic is roughly this: When considering if a 
candidate item has a locking conflict with a running item, then if 
*either* of them has a locking dependency that coincides with *any* 
dependency of the other item, then the candidate is rejected. The 
principle is that we don't give any item a chance to block on a lock.

cheers

andrew