Amit Kapila <amit.kap...@huawei.com> writes:
> On Friday, February 08, 2013 12:00 AM Tom Lane wrote:
> As per my understanding, currently in code wherever Result node can be
> avoided,
> it calls function is_projection_capable_plan(), so we can even enhance
> is_projection_capable_plan()
> so that it can also verify the expressions of tlists. But for this we need
> to change at all places
> from where is_projection_capable_plan() is called.
Hm. Really there's a whole dance that typically goes on, which is like
if (!is_projection_capable_plan(result_plan))
{
result_plan = (Plan *) make_result(root,
sub_tlist,
NULL,
result_plan);
}
else
{
/*
* Otherwise, just replace the subplan's flat tlist with
* the desired tlist.
*/
result_plan->targetlist = sub_tlist;
}
Perhaps we could encapsulate this whole sequence into a function called
say assign_targetlist_to_plan(), which would have the responsibility to
decide whether a Result node needs to be inserted.
regards, tom lane
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