Re: Oddity in EXPLAIN for foreign/custom join pushdown plans - Mailing list pgsql-hackers

From Kouhei Kaigai
Subject Re: Oddity in EXPLAIN for foreign/custom join pushdown plans
Date
Msg-id 9A28C8860F777E439AA12E8AEA7694F801211E34@BPXM15GP.gisp.nec.co.jp
Whole thread Raw
In response to Re: Oddity in EXPLAIN for foreign/custom join pushdown plans  (Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>)
Responses Re: Oddity in EXPLAIN for foreign/custom join pushdown plans  (Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>)
List pgsql-hackers
> On 2016/08/01 22:25, Kouhei Kaigai wrote:
> 
> I wrote:
> >>>     a broader
> >>>     word like "Processing" seems to work well because we allow various
> >>>     kinds of operations to the remote side, in addition to scans/joins,
> >>>     to be performed in that one Foreign Scan node indicated by "Foreign
> >>>     Processing", such as aggregation, window functions, distinct, order
> >>>     by, row locking, table modification, or combinations of them.
> 
>  >> On 2016/07/29 13:28, Ashutosh Bapat wrote:
> >>> "Scan" is a better word than "Processing". From plan's perspective it's
> >>> ultimately a Scan (on the data produced by the foreign server) and not
> >>> processing.
> 
> I wrote:
> >> Exactly, but one thing I'm concerned about is the table modification
> >> case; the EXPLAIN output would be something like this:
> >>
> >>    Foreign Scan
> >>      Remote SQL: INSERT INTO remote_table VALUES ...
> >>
> >> That would be strange, so I think a more broader word is better.  I
> >> don't think "Foreign Processing" is best.  "Foreign Upper" might be much
> >> better because the corresponding path is created by calling
> >> GetForeignUpperPaths.
> 
> > Be "Foreign %s", and gives "Insert" label by postgres_fdw; which knows
> > the ForeignScan node actually insert tuples.
> > From the standpoint of users, it looks "Foreign Insert".
> 
> My concern here is EXPLAIN for foreign joins.  I think it's another
> problem how we handle Foreign Scan plan nodes representing
> post-scan/join operations in EXPLAIN, so I'd like to leave that for
> another patch.
>
What is the post-scan/join operations? Are you saying EPQ recheck and
alternative local join plan?

Thanks,
--
NEC Business Creation Division / PG-Strom Project
KaiGai Kohei <kaigai@ak.jp.nec.com>


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