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

On 2010-12-30 9:02 AM +0200, Greg Smith wrote:
> Marko Tiikkaja wrote:
>> I have no idea why it worked in the past, but the patch was never
>> designed to work for UPSERT.  This has been discussed in the past and
>> some people thought that that's not a huge deal.
>
> It takes an excessively large lock when doing UPSERT, which means its
> performance under a heavy concurrent load can't be good.  The idea is
> that if the syntax and general implementation issues can get sorted out,
> fixing the locking can be a separate performance improvement to be
> implemented later.  Using MERGE for UPSERT is the #1 use case for this
> feature by a gigantic margin.  If that doesn't do what's expected, the
> whole implementation doesn't provide the community anything really worth
> talking about.  That's why I keep hammering on this particular area in
> all my testing.

I'm confused.  Are you saying that the patch is supposed to lock the 
table against concurrent INSERT/UPDATE/DELETE/MERGE?  Because I don't 
see it in the patch, and the symptoms you're having are a clear 
indication of the fact that it's not happening.  I also seem to recall 
that people thought locking the table would be excessive.


Regards,
Marko Tiikkaja