dblink_connect(text connstr) returns text dblink_connect(text connname, text connstr) returns text
dblink_connect() 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 postgresql_fdw_validator when defining the
corresponding foreign-data wrapper. See the example below, as
well as the following: CREATE FOREIGN DATA
WRAPPER, CREATE SERVER,
CREATE USER MAPPING
The name to use for this connection; if omitted, an unnamed connection is opened, replacing any existing unnamed connection.
libpq-style connection
info string, for example hostaddr=127.0.0.1 port=5432 dbname=mydb
user=postgres password=mypasswd. For details see
PQconnectdb in Section 31.1.
Returns status, which is always OK (since any error causes the function to throw an error instead of returning).
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.
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 USER dblink_regression_test WITH PASSWORD 'secret';
CREATE FOREIGN DATA WRAPPER postgresql VALIDATOR postgresql_fdw_validator;
CREATE SERVER fdtest FOREIGN DATA WRAPPER postgresql OPTIONS (hostaddr '127.0.0.1', dbname 'contrib_regression');
CREATE USER MAPPING FOR dblink_regression_test SERVER fdtest OPTIONS (user 'dblink_regression_test', password 'secret');
GRANT USAGE ON FOREIGN SERVER fdtest TO dblink_regression_test;
GRANT SELECT ON TABLE foo TO dblink_regression_test;
\set ORIGINAL_USER :USER
\c - dblink_regression_test
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 dblink_regression_test;
REVOKE SELECT ON TABLE foo FROM dblink_regression_test;
DROP USER MAPPING FOR dblink_regression_test SERVER fdtest;
DROP USER dblink_regression_test;
DROP SERVER fdtest;
DROP FOREIGN DATA WRAPPER postgresql;