postgresql/contrib/dblink/doc/query
Tom Lane 6f7fc0bade Cause initdb to create a third standard database "postgres", which
unlike template0 and template1 does not have any special status in
terms of backend functionality.  However, all external utilities such
as createuser and createdb now connect to "postgres" instead of
template1, and the documentation is changed to encourage people to use
"postgres" instead of template1 as a play area.  This should fix some
longstanding gotchas involving unexpected propagation of database
objects by createdb (when you used template1 without understanding
the implications), as well as ameliorating the problem that CREATE
DATABASE is unhappy if anyone else is connected to template1.
Patch by Dave Page, minor editing by Tom Lane.  All per recent
pghackers discussions.
2005-06-21 04:02:34 +00:00

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==================================================================
Name
dblink -- Returns a set from a remote database
Synopsis
dblink(text connstr, text sql [, bool fail_on_error])
dblink(text connname, text sql [, bool fail_on_error])
dblink(text sql [, bool fail_on_error])
Inputs
connname
connstr
If two arguments are present, the first is first assumed to be a specific
connection name to use. If the name is not found, the argument is then
assumed to be a valid connection string, of standard libpq format,
e.g.: "hostaddr=127.0.0.1 dbname=mydb user=postgres password=mypasswd"
If only one argument is used, then the unnamed connection is used.
sql
sql statement that you wish to execute on the remote host
e.g. "select * from pg_class"
fail_on_error
If true (default when not present) then an ERROR thrown on the remote side
of the connection causes an ERROR to also be thrown locally. If false, the
remote ERROR is locally treated as a NOTICE, and no rows are returned.
Outputs
Returns setof record
Example usage
select * from dblink('dbname=postgres','select proname, prosrc from pg_proc')
as t1(proname name, prosrc text) where proname like 'bytea%';
proname | prosrc
------------+------------
byteacat | byteacat
byteaeq | byteaeq
bytealt | bytealt
byteale | byteale
byteagt | byteagt
byteage | byteage
byteane | byteane
byteacmp | byteacmp
bytealike | bytealike
byteanlike | byteanlike
byteain | byteain
byteaout | byteaout
(12 rows)
select dblink_connect('dbname=postgres');
dblink_connect
----------------
OK
(1 row)
select * from dblink('select proname, prosrc from pg_proc')
as t1(proname name, prosrc text) where proname like 'bytea%';
proname | prosrc
------------+------------
byteacat | byteacat
byteaeq | byteaeq
bytealt | bytealt
byteale | byteale
byteagt | byteagt
byteage | byteage
byteane | byteane
byteacmp | byteacmp
bytealike | bytealike
byteanlike | byteanlike
byteain | byteain
byteaout | byteaout
(12 rows)
select dblink_connect('myconn','dbname=regression');
dblink_connect
----------------
OK
(1 row)
select * from dblink('myconn','select proname, prosrc from pg_proc')
as t1(proname name, prosrc text) where proname like 'bytea%';
proname | prosrc
------------+------------
bytearecv | bytearecv
byteasend | byteasend
byteale | byteale
byteagt | byteagt
byteage | byteage
byteane | byteane
byteacmp | byteacmp
bytealike | bytealike
byteanlike | byteanlike
byteacat | byteacat
byteaeq | byteaeq
bytealt | bytealt
byteain | byteain
byteaout | byteaout
(14 rows)
==================================================================
A more convenient way to use dblink may be to create a view:
create view myremote_pg_proc as
select *
from dblink('dbname=postgres','select proname, prosrc from pg_proc')
as t1(proname name, prosrc text);
Then you can simply write:
select * from myremote_pg_proc where proname like 'bytea%';