Re: [PATCH] SQL assertions prototype

Jim Nasby <jim(at)nasby(dot)net> wrote:
> On 12/18/13, 1:42 PM, Kevin Grittner wrote:
>> Jim Nasby <jim(at)nasby(dot)net> wrote:
>>
>>> This is another case where it would be very useful to restrict
>>> what relations a transaction (or in this case, a substransaction)
>>> can access. If we had the ability to make that restriction then
>>> we could force assertions that aren't plain SQL to explicitly
>>> specify what tables the assert is going to hit, and if the assert
>>> tries to do something different then we throw an error.
>>>
>>> The ability to restrict object access within a transaction would
>>> also benefit VACUUM and possibly the Changeset stuff.
>>
>> I'm pretty sure that SSI could also optimize based on that,
>> although there are probably about 10 other optimizations that would
>> be bigger gains before getting to that.
>
> Any ideas how hard this would be?

If we had a list to check against, I think it would be possible to
do this during parse analysis and AcquireRewriteLocks().  (One or
the other happens before query rewrite.)  The hard part seems to me
to be defining a sane way to get the list.

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company