(2014/07/01 15:13), Ashutosh Bapat wrote:
On Tue, Jul 1, 2014 at 7:39 AM, Etsuro Fujita
<fujita.ets...@lab.ntt.co.jp <mailto:fujita.ets...@lab.ntt.co.jp>> wrote:

We may want to modify use_physical_tlist(), to return false, in case of
foreign tables. BTW, it does return false for inheritance trees.

Yeah, but please consider cases where foreign tables are not inheritance child rels (and any system columns are requested).

  486     /*
  487      * Can't do it with inheritance cases either (mainly because
  488      * doesn't project).
  489      */
  490     if (rel->reloptkind != RELOPT_BASEREL)
  491         return false;

    Yeah, we can call build_physical_tlist() (and do that in some
    cases), but if we call the function, it would generate a tlist that
    contains all Vars in the relation, not only those Vars actually
    needed by the query (ie, Vars in reltargetlist), and thus it would
    take more cycles to compute attr_used from the tlist than from
    reltargetlist.  That' what I wanted to say.

Maybe I'm missing something, but what's the point of using the tlist, not reltargetlist?


Best regards,
Etsuro Fujita

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