Re: BUG #15642: UPDATE statements that change a partition key and FDW partitions problem.

(2019/02/19 23:13), PG Bug reporting form wrote:
> The following bug has been logged on the website:

> Update statement which changes value of partition key doesn't doesn't work
> with FDW partitions.
>
> Test script:
> \c postgres
> drop database IF EXISTS test;
> drop database IF EXISTS test0;
> drop database IF EXISTS test1;
> create database test;
> create database test0;
> create database test1;
> \c test0
> create table t (id integer not null, constraint id_check check (id<0));
> \c test1
> create table t (id integer not null, constraint id_check check (id>=0));
> \c test
> create extension postgres_fdw;
> create server if not exists test0 FOREIGN DATA WRAPPER postgres_fdw OPTIONS
> (dbname 'test0');
> create server if not exists test1 FOREIGN DATA WRAPPER postgres_fdw OPTIONS
> (dbname 'test1');
> CREATE USER MAPPING FOR public SERVER test0 OPTIONS (user 'postgres');
> CREATE USER MAPPING FOR public SERVER test1 OPTIONS (user 'postgres');
> CREATE FOREIGN TABLE t0 (id integer not null, constraint id_check check
> (id<0) ) SERVER test0 OPTIONS (table_name 't');
> CREATE FOREIGN TABLE t1 (id integer not null, constraint id_check check
> (id>=0)) SERVER test1 OPTIONS (table_name 't');
> create table t (id integer not null) partition by range (id);
> alter table t ATTACH PARTITION t0 for values from (MINVALUE) to (0);
> alter table t ATTACH PARTITION t1 for values from (0) to (MAXVALUE);
> insert into t (id) values (-1);
> update t set id=2 where id=-1;
>
> Expected: row in t1 partition.
> Reality:
> test=# update t set id=2 where id=-1;
> ERROR: new row for relation "t" violates check constraint "id_check"
> DETAIL: Failing row contains (2).
> CONTEXT: remote SQL command: UPDATE public.t SET id = 2 WHERE ((id =
> (-1)))
>
> I don't know is this case supposed to work or not, and I can't find any
> related notes in documentation.

Unfortunately, this is not supported as documented in the notes section
of the UPDATE reference page [1]:

"Currently, rows cannot be moved from a partition that is a foreign
table to some other partition, but they can be moved into a foreign
table if the foreign data wrapper supports it."

Best regards,
Etsuro Fujita

[1] https://www.postgresql.org/docs/11/sql-update.html