Re: FDW: possible resjunk columns in AddForeignUpdateTargets

2013/11/6 Albe Laurenz <laurenz.albe@wien.gv.at>:
> I have a question concerning the Foreign Data Wrapper API:
>
> I find no mention of this in the documentation, but I remember that
> you can only add a resjunk column that matches an existing attribute
> of the foreign table and not one with an arbitrary name or
> definition.
>
> Ist that right?

My understanding (having recently had a crack at getting an FDW working)
is that the name can be arbitrary within reason - at least that's what
I get from this bit of the documentation:

> To do that, add TargetEntry items to parsetree->targetList, containing
> expressions for the extra values to be fetched. Each such entry must
> be marked resjunk = true, and > must have a distinct resname that will
> identify it at execution time. Avoid using names matching ctidN or
> wholerowN, as the core system can generate junk columns of these names.

http://www.postgresql.org/docs/9.3/interactive/fdw-callbacks.html#FDW-CALLBACKS-UPDATE

Someone more knowledgeable than myself will know better, I hope.

Regards

Ian Barwick