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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;