Re: Display of multi-target-table Modify plan nodes in EXPLAIN

Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com> writes:
> On Mon, Mar 23, 2015 at 10:51 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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