Re: [HACKERS] [GENERAL] Using Cursor in PostgreSQL 7.2 - Mailing list pgsql-patches

Tom Lane wrote:

> Joe Conway <joseph.conway@home.com> writes:
>
>>I confirmed the UNION hack is no longer required. Thanks! Is it too late
>>to change the README in contrib/dblink?
>>
>
> No, I don't think that's a problem.  Send a patch.
>

Here's a (documentation only) patch for the contrib/dblink README.

Thanks,

Joe
*** README.dblink.orig    Mon Jun 18 12:09:50 2001
--- README.dblink    Wed Dec 12 19:57:34 2001
***************
*** 82,88 ****

  Example usage

!   select dblink('hostaddr=127.0.0.1 port=5432 dbname=mydb user=postgres password=mypasswd','select f1, f2 from
mytable');


  ==================================================================
--- 82,89 ----

  Example usage

!   select dblink('hostaddr=127.0.0.1 port=5432 dbname=mydb user=postgres password=mypasswd'
!                ,'select f1, f2 from mytable');


  ==================================================================
***************
*** 118,161 ****

  ==================================================================

! NOTE: If you need to provide selection criteria in a WHERE clause, it is necessary
! to 'fake' a UNION, e.g.

!   select
!      dblink_tok(t1.dblink_p,0) as f1
!     ,dblink_tok(t1.dblink_p,1) as f2
!   from
!    (
!     select dblink(
!                    'hostaddr=127.0.0.1 port=5432 dbname=mydb user=postgres password=mypasswd'
!                   ,'select f1, f2 from mytable'
!                  ) as dblink_p
!     union all
!     select null where false
!    ) as t1
!   where
!     dblink_tok(t1.dblink_p,0) = 'mycriteria';
!
! in order to work around an issue with the query optimizer. A more convenient way to approach
! this problem is to create a view:
!
!   create view myremotetable as
!   select
!      dblink_tok(t1.dblink_p,0) as f1
!     ,dblink_tok(t1.dblink_p,1) as f2
!   from
!    (
!     select dblink(
!                    'hostaddr=127.0.0.1 port=5432 dbname=mydb user=postgres password=mypasswd'
!                   ,'select f1, f2 from mytable'
!                  ) as dblink_p
!     union all
!     select null where false
!    ) as t1;

  Then you can simply write:

!    select f1,f2 from myremotetable where f1 = 'mycriteria';

  ==================================================================

--- 119,134 ----

  ==================================================================

! A more convenient way to use dblink may be to create a view:

!  create view myremotetable as
!  select dblink_tok(t1.dblink_p,0) as f1, dblink_tok(t1.dblink_p,1) as f2
!  from (select dblink('hostaddr=127.0.0.1 port=5432 dbname=template1 user=postgres password=postgres'
!                     ,'select proname, prosrc from pg_proc') as dblink_p) as t1;

  Then you can simply write:

!    select f1, f2 from myremotetable where f1 like 'bytea%';

  ==================================================================