Re: Re: new patch of MERGE (merge_204) & a question about duplicated ctid

On 2011-01-04 6:27 PM, David Fetter wrote:
> On Tue, Jan 04, 2011 at 04:44:32AM -0500, Greg Smith wrote:
>> Heikki Linnakangas wrote:
>>> You can of course LOCK TABLE as a work-around, if that's what you want.
>>
>> Presuming the code quality issues and other little quirks I've
>> documented (and new ones yet to be discovered) can get resolved
>> here, and that's a sizeable open question, I could see shipping this
>> with the automatic heavy LOCK TABLE in there.  Then simple UPSERT
>> could work out of the box via a straightforward MERGE.
>
> How about implementing an UPSERT command as "take the lock, do the
> merge?"  That way, we'd have both the simplicity for the simpler cases
> and a way to relax consistency guarantees for those who would like to
> do so.

That, unfortunately, won't work so well in REPEATABLE READ :-(  But I, 
too, am starting to think that we should have a separate, optimized 
command to do UPSERT/INSERT .. IGNORE efficiently and correctly while 
making MERGE's correctness the user's responsibility.  Preferably with 
huge warning signs on the documentation page.


Regards,
Marko Tiikkaja