(2014/06/30 20:17), Ashutosh Bapat wrote:
On Mon, Jun 30, 2014 at 4:17 PM, Etsuro Fujita
<fujita.ets...@lab.ntt.co.jp <mailto:fujita.ets...@lab.ntt.co.jp>> wrote:

    (2014/06/30 17:47), Ashutosh Bapat wrote:

        BTW, why aren't you using the tlist passed to this function? I guess
        create_scan_plan() passes tlist after processing it, so that
        should be
        used rather than rel->reltargetlist.

    I think that that would be maybe OK, but I think that it would not
    be efficient to use the list to compute attrs_used, because the
    tlist would have more information than rel->reltargetlist in cases
    where the tlist is build through build_physical_tlist().

In that case, we can call build_relation_tlist() for foreign tables.

Do you mean build_physical_tlist()?

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.


Best regards,
Etsuro Fujita

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