Re: MERGE Specification

On 4/25/08, Robert Treat <xzilla@users.sourceforge.net> wrote:
> On Thursday 24 April 2008 23:40, Tom Lane wrote:
>  > Robert Treat <xzilla@users.sourceforge.net> writes:
>  > > Perhaps a better option would be to implement Merge per spec, and then
>  > > implement a "replace into" command for the oltp scenario.  This way you
>  > > keep the spec behavior for the spec syntax, and have a clearly non-spec
>  > > command for non-spec behavior.
>  >
>  > In that case, it's a fair question to ask just who will use the "spec"
>  > syntax.  As far as I can tell from years of watching the mailing lists,
>  > there is plenty of demand for a concurrent-safe insert-or-update
>  > behavior, and *exactly zero* demand for the other.  I challenge you to
>  > find even one request for the "spec" behavior in the mailing list
>  > archives.  (Simon doesn't count.)
>  >
>
>
> AIUI the current implementation is designed to avoid race conditions partially
>  at the cost of being insert friendly and somewhat update unfriendly. My guess
>  is that most of the people wanting this for OLTP use want an update friendly
>  implementation (that's certainly been the majority of cases I've needed
>  myself, and that I have seen others use).

This seems to hint that there should be 2 variants of merge/upsert
- insert-friendly and update-friendly...  It seems unlikely one implementation
can be both.  And especially bad would be implementation that is neither.

-- 
marko