Re: [Proposal] Global temporary tables

> 2020年3月16日 下午2:23，Prabhat Sahu <prabhat(dot)sahu(at)enterprisedb(dot)com> 写道：
>
> Hi Wenjing,
> Please check the below scenario, where the Foreign table on GTT not showing records.
>
> postgres=# create extension postgres_fdw;
> CREATE EXTENSION
> postgres=# do $d$
> begin
> execute $$create server fdw foreign data wrapper postgres_fdw options (host 'localhost',dbname 'postgres',port '$$||current_setting('port')||$$')$$;
> end;
> $d$;
> DO
> postgres=# create user mapping for public server fdw;
> CREATE USER MAPPING
>
> postgres=# create table lt1 (c1 integer, c2 varchar(50));
> CREATE TABLE
> postgres=# insert into lt1 values (1,'c21');
> INSERT 0 1
> postgres=# create foreign table ft1 (c1 integer, c2 varchar(50)) server fdw options (table_name 'lt1');
> CREATE FOREIGN TABLE
> postgres=# select * from ft1;
> c1 | c2
> ----+-----
> 1 | c21
> (1 row)
>
> postgres=# create global temporary table gtt1 (c1 integer, c2 varchar(50));
> CREATE TABLE
> postgres=# insert into gtt1 values (1,'gtt_c21');
> INSERT 0 1
> postgres=# create foreign table f_gtt1 (c1 integer, c2 varchar(50)) server fdw options (table_name 'gtt1');
> CREATE FOREIGN TABLE
>
> postgres=# select * from gtt1;
> c1 | c2
> ----+---------
> 1 | gtt_c21
> (1 row)
>
> postgres=# select * from f_gtt1;
> c1 | c2
> ----+----
> (0 rows)
>
> --

I understand that postgre_fdw works similar to dblink.
postgre_fdw access to the table requires a new connection.
The data in the GTT table is empty in the newly established connection.
Because GTT shares structure but not data between connections.

Try local temp table:
create temporary table ltt1 (c1 integer, c2 varchar(50));

insert into ltt1 values (1,'gtt_c21');

create foreign table f_ltt1 (c1 integer, c2 varchar(50)) server fdw options (table_name 'ltt1');

select * from ltt1;
c1 | c2
----+---------
1 | gtt_c21
(1 row)

select * from l_gtt1;
ERROR: relation "l_gtt1" does not exist
LINE 1: select * from l_gtt1;

Wenjing

> With Regards,
> Prabhat Kumar Sahu
> EnterpriseDB: http://www.enterprisedb.com <http://www.enterprisedb.com/>