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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() 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 options=-csearch_path=. For details see
           Section 34.1.1. 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

       If untrusted users have access to a database that has not adopted a secure schema usage
       pattern, begin each session by removing publicly-writable schemas from search_path. One
       could, for example, add options=-csearch_path= to connstr. This consideration is not
       specific to dblink; it applies to every interface for executing arbitrary SQL commands.

       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 options=-csearch_path=');
            dblink_connect
           ----------------
            OK
           (1 row)

           SELECT dblink_connect('myconn', 'dbname=postgres options=-csearch_path=');
            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;