On 2017/01/19 12:26, Ashutosh Bapat wrote:
On Thu, Jan 19, 2017 at 2:14 AM, Robert Haas <robertmh...@gmail.com> wrote:
On Fri, Jan 13, 2017 at 6:22 AM, Etsuro Fujita
<fujita.ets...@lab.ntt.co.jp> wrote:
My biggest concern about GetExistingLocalJoinPath is that might not be
extendable to the case of foreign-join paths with parameterization; in which
case, fdw_outerpath for a given foreign-join path would need to have the
same parameterization as the foreign-join path, but there might not be any
existing paths with the same parameterization in the path list.
I agree that this is a problem.
Effectively, it means that foreign join path creation will have a
parameterization different (per add_path()) from any local join
produced. But why would it be so?
I think it's better to give the FDW a chance to do that because the FDW
might have more knowledge about the parameterization for joinrels than core.
The parameterization bubbles up from
the base relation. The process for creating parameterized local and
foreign paths for a base relation is same. Thus we will have same
parameterizations considered for foreign as well as local joins. Those
different parameterizations will be retained add_path(), so we should
find one there
Is that right? I think there would be cases where we can't find one
because add_path removes paths dominated by others.
Best regards,
Etsuro Fujita
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