Re: Making Vars outer-join aware
| От | Richard Guo |
|---|---|
| Тема | Re: Making Vars outer-join aware |
| Дата | |
| Msg-id | CAMbWs49iXxG=Br9CcvntrN5X1MVnu-SEP0SosfbcnBvrgqVipA@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Making Vars outer-join aware (Tom Lane <tgl@sss.pgh.pa.us>) |
| Ответы |
Re: Making Vars outer-join aware
|
| Список | pgsql-hackers |
On Thu, Aug 25, 2022 at 5:18 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
Richard Guo <guofenglinux@gmail.com> writes:
> Do we need to also
> generate two SpecialJoinInfos for the B/C join in the first order, with
> and without the A/B join in its min_lefthand?
No, the SpecialJoinInfos would stay as they are now. It's already the
case that the first join's min_righthand would contain only B, and
the second one's min_righthand would contain only C.
I'm not sure if I understand it correctly. If we are given the first
order from the parser, the SpecialJoinInfo for the B/C join would have
min_lefthand as containing both B and the A/B join. And this
SpecialJoinInfo would make the B/C join be invalid, which is not what we
want. Currently the patch resolves this by explicitly running
remove_unneeded_nulling_relids, and the A/B join would be removed from
B/C join's min_lefthand, if Pbc is strict for B.
Do we still need this kind of fixup if we are to keep just one form of
SpecialJoinInfo and two forms of RestrictInfos?
Thanks
Richard
order from the parser, the SpecialJoinInfo for the B/C join would have
min_lefthand as containing both B and the A/B join. And this
SpecialJoinInfo would make the B/C join be invalid, which is not what we
want. Currently the patch resolves this by explicitly running
remove_unneeded_nulling_relids, and the A/B join would be removed from
B/C join's min_lefthand, if Pbc is strict for B.
Do we still need this kind of fixup if we are to keep just one form of
SpecialJoinInfo and two forms of RestrictInfos?
Thanks
Richard
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