Re: [PATCH] SQL assertions prototype

On 12/17/2013 01:42 PM, Kevin Grittner wrote:
> Josh Berkus <josh(at)agliodbs(dot)com> wrote:
>> Going back over this patch, I haven't seen any further discussion of the
>> point Heikki raises above, which seems like a bit of a showstopper.
>>
>> Heikki, did you have specific ideas on how to solve this? Right now my
>> mind boggles.
>
> It works fine as long as you set default_transaction_isolation =
> 'serializable' and never override that. :-) Of course, it sure
> would be nice to have a way to prohibit overrides, but that's
> another issue.
>
> Otherwise it is hard to see how to make it work in a general way
> without a mutually exclusive lock mode on the table for the
> duration of any transaction which modifies the table.

Serializable or not, *what* do we lock for assertions? It's not rows.
Tables? Which tables? What if the assertion is an interpreted language
function? Does the SSI reference counter really take care of all of this?

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com