Ashutosh Bapat <ashutosh.ba...@enterprisedb.com> writes:
> On Mon, Mar 23, 2015 at 10:51 AM, Tom Lane <t...@sss.pgh.pa.us> wrote:
>> Hm?  We don't have scan nodes that read more than one table, so I'm
>> not following your point.

> But in the text output you gave
> Update on public.pt1  (cost=0.00..321.05 rows=3541 width=46)
>    Update on public.pt1
>    Foreign Update on public.ft1
>      Remote SQL: UPDATE public.ref1 SET c1 = $2 WHERE ctid = $1
>    Foreign Update on public.ft2
>      Remote SQL: UPDATE public.ref2 SET c1 = $2 WHERE ctid = $1
>    Update on public.child3
>    ->  Seq Scan on public.pt1  (cost=0.00..0.00 rows=1 width=46)
>          Output: (pt1.c1 + 1), pt1.c2, pt1.c3, pt1.ctid
>    ... etc ...

> For ft1 there is only Update Remote SQL. whereas for child3 you have
> specified the Seq Scan as well.

I think you're confused by my perhaps-overly-abbreviated example.
Here's the whole output for the example in HEAD:

# explain update pt1 set c1=c1+1;
                             QUERY PLAN                              
---------------------------------------------------------------------
 Update on pt1  (cost=0.00..321.05 rows=3541 width=46)
   Update on pt1
   Foreign Update on ft1
   Foreign Update on ft2
   Update on child3
   ->  Seq Scan on pt1  (cost=0.00..0.00 rows=1 width=46)
   ->  Foreign Scan on ft1  (cost=100.00..148.03 rows=1170 width=46)
   ->  Foreign Scan on ft2  (cost=100.00..148.03 rows=1170 width=46)
   ->  Seq Scan on child3  (cost=0.00..25.00 rows=1200 width=46)
(9 rows)

# explain verbose update pt1 set c1=c1+1;
                                 QUERY PLAN                                 
----------------------------------------------------------------------------
 Update on public.pt1  (cost=0.00..321.05 rows=3541 width=46)
   Update on public.pt1
   Foreign Update on public.ft1
     Remote SQL: UPDATE public.ref1 SET c1 = $2 WHERE ctid = $1
   Foreign Update on public.ft2
     Remote SQL: UPDATE public.ref2 SET c1 = $2 WHERE ctid = $1
   Update on public.child3
   ->  Seq Scan on public.pt1  (cost=0.00..0.00 rows=1 width=46)
         Output: (pt1.c1 + 1), pt1.c2, pt1.c3, pt1.ctid
   ->  Foreign Scan on public.ft1  (cost=100.00..148.03 rows=1170 width=46)
         Output: (ft1.c1 + 1), ft1.c2, ft1.c3, ft1.ctid
         Remote SQL: SELECT c1, c2, c3, ctid FROM public.ref1 FOR UPDATE
   ->  Foreign Scan on public.ft2  (cost=100.00..148.03 rows=1170 width=46)
         Output: (ft2.c1 + 1), ft2.c2, ft2.c3, ft2.ctid
         Remote SQL: SELECT c1, c2, c3, ctid FROM public.ref2 FOR UPDATE
   ->  Seq Scan on public.child3  (cost=0.00..25.00 rows=1200 width=46)
         Output: (child3.c1 + 1), child3.c2, child3.c3, child3.ctid
(17 rows)


                        regards, tom lane


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