On 1/4/23 12:57, Alvaro Herrera wrote:
I haven't read this patch other than superficially; I suppose the feature it's introducing is an OK one to have as an extension to the standard. (I hope the community members that are committee members will propose this extension to become part of the standard.)
I have been doing some research on this, reading the original papers that introduced the feature and its improvements.
I don't see anything that ever considered what this patch proposes, even though SQL Server has it. (The initial MERGE didn't even have DELETE!)
SOURCE and TARGET are not currently keywords, but the only things that can come after MATCHED are THEN and AND, so I don't foresee any issues with us implementing this before the committee accepts such a change proposal. I also don't see how the committee could possibly change the semantics of this, and two implementations having it is a good argument for getting it in.
We should be cautious in doing something differently from SQL Server here, and I would appreciate any differences being brought to my attention so I can incorporate them into a specification, even if that means resorting to the hated "implementation-defined".
-- Vik Fearing
