Re: Pre-set Hint bits/VACUUM FREEZE on data load..?

On Fri, Mar 25, 2011 at 4:00 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> On 25.03.2011 09:51, Heikki Linnakangas wrote:
>>
>> I don't think we should put the onus on the user to choose the right
>> data loading mode. If we can reliably detect the cases where it's safe
>> do these tricks, we can transparently apply them when possible. I would
>> be cool with tricks that apply only in narrow cases, as long as we don't
>> require the user to do anything.
>
> I believe the conditions for being able to set hint bits immediately at COPY
> are:
>
> 1. The table has been created or truncated in the same transaction
> 2. We are not in a subtransaction (or the table was created and truncated in
> the same subtransaction)
> 3. There are no open portals
> 4. Executing the COPY doesn't need to run any "unsafe" code that might
> access the same table. This includes triggers, check constraints and input
> functions. An expression is safe if it is immutable.

That's not enough... some other transaction could see the data before
the transaction commits.

--
Robert Haas
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