DBLINK_CONNECT(3) PostgreSQL 9.2.7 Documentation DBLINK_CONNECT(3)NAMEdblink_connect - opens a persistent connection to a remote database
SYNOPSIS
dblink_connect(text connstr) returns text
dblink_connect(text connname, text connstr) returns text
DESCRIPTIONdblink_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_FOREIGN_DATA_WRAPPER(7)), CREATE SERVER (CREATE_SERVER(7)),
CREATE USER MAPPING (CREATE_USER_MAPPING(7))
ARGUMENTS
conname
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 PQconnectdb in Section 31.1, “Database Connection Control
Functions”, in the documentation.
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 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;
PostgreSQL 9.2.7 2014-02-17 DBLINK_CONNECT(3)
