Andres Freund <andres@2ndquadrant.com> writes:
> On 2013-04-25 13:17:31 -0400, Tom Lane wrote:
>> Since we know that C.I.C. executes in its own transaction, and there
>> can't be more than one on the same table due to locking, it seems to me
>> that it'd be safe to drop our own snapshot before waiting for other
>> xacts to end. That is, we could just rearrange the last few steps in
>> DefineIndex(), taking care to save snapshot->xmin before we destroy the
>> snapshot so that we still have that value to pass to
>> GetCurrentVirtualXIDs().
>>
>> Anybody see a flaw in that solution?
> Except that it still will unnecessarily wait for other CICs, just not
> deadlock, I don't see a problem. We could have a PROC_IN_CIC flag or
> something so we can ignore other index creations, but I am not sure if
> its worth the complication.
I'm not sure it's a good idea to ignore other CICs altogether --- they
could be executing user-defined index functions that do strange things
like consult other tables. Since this seems to me to be a bit outside
the intended use-case for CIC anyway, I think it's good enough if they
just don't deadlock.
regards, tom lane