Well let's see what others think. Also, we might want to separate that information on result relations heading probably.
On Fri, Feb 6, 2015 at 1:35 PM, Etsuro Fujita <fujita.ets...@lab.ntt.co.jp> wrote: > Hi Ashutosh, > > Thank you for the review! > > > On 2015/02/03 15:32, Ashutosh Bapat wrote: > >> I agree that it's a problem, and it looks more severe when there are >> multiple children >> postgres=# create table parent (a int check (a < 0) no inherit); >> CREATE TABLE >> postgres=# create table child1 (a int check (a >= 0)); >> CREATE TABLE >> postgres=# create table child2 (a int check (a >= 0)); >> CREATE TABLE >> postgres=# create table child3 (a int check (a >= 0)); >> CREATE TABLE >> postgres=# alter table child1 inherit parent; >> ALTER TABLE >> postgres=# alter table child2 inherit parent; >> ALTER TABLE >> postgres=# alter table child3 inherit parent; >> ALTER TABLE >> postgres=# explain update parent set a = a * 2 where a >= 0; >> QUERY PLAN >> ---------------------------------------------------------------- >> Update on child1 (cost=0.00..126.00 rows=2400 width=10) >> -> Seq Scan on child1 (cost=0.00..42.00 rows=800 width=10) >> Filter: (a >= 0) >> -> Seq Scan on child2 (cost=0.00..42.00 rows=800 width=10) >> Filter: (a >= 0) >> -> Seq Scan on child3 (cost=0.00..42.00 rows=800 width=10) >> Filter: (a >= 0) >> (7 rows) >> >> It's certainly confusing why would an update on child1 cause scan on >> child*. >> > > Yeah, I think so too. > > But I also think that showing parent's name with Upate would be >> misleading esp. when user expects it to get filtered because of >> constraint exclusion. >> >> Instead, can we show all the relations that are being modified e.g >> Update on child1, child2, child3. That will disambiguate everything. >> > > That's an idea, but my concern about that is the cases where there are a > large number of child tables as the EXPLAIN would be difficult to read in > such cases. > > Best regards, > Etsuro Fujita > -- Best Wishes, Ashutosh Bapat EnterpriseDB Corporation The Postgres Database Company
