dblink_connect(3) PostgreSQL 9.6.6 Documentation dblink_connect(3)
NAME
dblink_connect - opens a persistent connection to a remote database
SYNOPSIS
dblink_connect(text connstr) returns text
dblink_connect(text connname, text connstr) returns text
DESCRIPTION
dblink_connect(3) establishes a connection to a remote PostgreSQL
database. The server and database to be contacted are identified
through a standard libpq connection string. Optionally, a name can be
assigned to the connection. Multiple named connections can be open at
once, but only one unnamed connection is permitted at a time. The
connection will persist until closed or until the database session is
ended.
The connection string may also be the name of an existing foreign
server. It is recommended to use the foreign-data wrapper dblink_fdw
when defining the foreign server. See the example below, as well as
CREATE SERVER (CREATE_SERVER(7)) and CREATE USER MAPPING
(CREATE_USER_MAPPING(7)).
ARGUMENTS
connname
The name to use for this connection; if omitted, an unnamed
connection is opened, replacing any existing unnamed connection.
connstr
libpq-style connection info string, for example hostaddr=127.0.0.1
port=5432 dbname=mydb user=postgres password=mypasswd. For details
see Section 32.1.1, "Connection Strings", in the documentation.
Alternatively, the name of a foreign server.
RETURN VALUE
Returns status, which is always OK (since any error causes the function
to throw an error instead of returning).
NOTES
Only superusers may use dblink_connect to create
non-password-authenticated connections. If non-superusers need this
capability, use dblink_connect_u instead.
It is unwise to choose connection names that contain equal signs, as
this opens a risk of confusion with connection info strings in other
dblink functions.
EXAMPLES
SELECT dblink_connect('dbname=postgres');
dblink_connect
----------------
OK
(1 row)
SELECT dblink_connect('myconn', 'dbname=postgres');
dblink_connect
----------------
OK
(1 row)
-- FOREIGN DATA WRAPPER functionality
-- Note: local connection must require password authentication for this to work properly
-- Otherwise, you will receive the following error from dblink_connect():
-- ----------------------------------------------------------------------
-- ERROR: password is required
-- DETAIL: Non-superuser cannot connect if the server does not request a password.
-- HINT: Target server's authentication method must be changed.
CREATE SERVER fdtest FOREIGN DATA WRAPPER dblink_fdw OPTIONS (hostaddr '127.0.0.1', dbname 'contrib_regression');
CREATE USER regress_dblink_user WITH PASSWORD 'secret';
CREATE USER MAPPING FOR regress_dblink_user SERVER fdtest OPTIONS (user 'regress_dblink_user', password 'secret');
GRANT USAGE ON FOREIGN SERVER fdtest TO regress_dblink_user;
GRANT SELECT ON TABLE foo TO regress_dblink_user;
\set ORIGINAL_USER :USER
\c - regress_dblink_user
SELECT dblink_connect('myconn', 'fdtest');
dblink_connect
----------------
OK
(1 row)
SELECT * FROM dblink('myconn','SELECT * FROM foo') AS t(a int, b text, c text[]);
a | b | c
----+---+---------------
0 | a | {a0,b0,c0}
1 | b | {a1,b1,c1}
2 | c | {a2,b2,c2}
3 | d | {a3,b3,c3}
4 | e | {a4,b4,c4}
5 | f | {a5,b5,c5}
6 | g | {a6,b6,c6}
7 | h | {a7,b7,c7}
8 | i | {a8,b8,c8}
9 | j | {a9,b9,c9}
10 | k | {a10,b10,c10}
(11 rows)
\c - :ORIGINAL_USER
REVOKE USAGE ON FOREIGN SERVER fdtest FROM regress_dblink_user;
REVOKE SELECT ON TABLE foo FROM regress_dblink_user;
DROP USER MAPPING FOR regress_dblink_user SERVER fdtest;
DROP USER regress_dblink_user;
DROP SERVER fdtest;
PostgreSQL 9.6.6 2017 dblink_connect(3)
PostgreSQL 9.6.6 - Generated Fri Dec 1 19:43:33 CST 2017