Re: Odd system-column handling in postgres_fdw join pushdown patch

On 2016/03/23 13:44, Ashutosh Bapat wrote:
> An FDW can choose not to use those functions, so I don't see a
> connection between scan list having simple Vars and existence of those
> functions (actually a single one). But having those function would
> minimize the code that each FDW has to write, in case they want those
> functions. E.g. we have to translate Var::varno to tableoid in case
> that's requested by pulling RTE and then getting oid out from there. If
> that functionality is available in the core, 1. the code is not
> duplicated 2. every FDW will get the same tableoid. Similarly for the
> other columns.

OK.  Then, I'd like to propose a function that would create interger 
Lists of indexes of tableoids, xids and cids plus an OID List of these 
tableoids, in a given fdw_scan_tlist, on the assumption that each 
expression in the fdw_scan_tlist is a simple Var.  I'd also like to 
propose another function that would fill system columns using these 
Lists when creating a scan tuple.

Best regards,
Etsuro Fujita