Andres Freund <andres@2ndquadrant.com> wrote:
> On 2014-09-29 14:57:45 -0700, Kevin Grittner wrote:
>> The initial implementation could restrict to these exact clauses
>> and require that the boolean-expression used equality-quals on all
>> columns of a unique index on only NOT NULL columns.
>
> That'll make it really hard to actually implement real MERGE.
>
> Because suddenly there's no way for the user to know whether he's
> written a ON condition that can implement UPSERT like properties
> (i.e. the *precise* column list of an index) or not.
Well, unless we abandon transactional semantics for other MERGE
statements, we should have a way that UPSERT logic continues to
work if you don't match a suitable index; it will just be slower --
potentially a lot slower, but that's what indexes are for. I don't
think we need a separate statement type for the one we "do well",
because I don't think we should do the other one without proper
transactional semantics.
--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
