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>dblink_connect</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN116081"
></A
><H2
>Name</H2
>dblink_connect -- opens a persistent connection to a remote database</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN116084"
></A
><H2
>Synopsis</H2
><PRE
CLASS="SYNOPSIS"
> dblink_connect(text connstr) returns text
dblink_connect(text connname, text connstr) returns text
</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN116086"
></A
><H2
>Description</H2
><P
> <CODE
CLASS="FUNCTION"
>dblink_connect()</CODE
> establishes a connection to a remote
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> database. The server and database to
be contacted are identified through a standard <SPAN
CLASS="APPLICATION"
>libpq</SPAN
>
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.
</P
><P
> The connection string may also be the name of an existing foreign
server. It is recommended to use
the <CODE
CLASS="FUNCTION"
>postgresql_fdw_validator</CODE
> when defining
the corresponding foreign-data wrapper. See the example below, as
well as the following:
<A
HREF="sql-createforeigndatawrapper.html"
><I
>CREATE FOREIGN DATA WRAPPER</I
></A
>, <A
HREF="sql-createserver.html"
><I
>CREATE SERVER</I
></A
>, <A
HREF="sql-createusermapping.html"
><I
>CREATE USER MAPPING</I
></A
>
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN116101"
></A
><H2
>Arguments</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="PARAMETER"
>conname</TT
></DT
><DD
><P
> The name to use for this connection; if omitted, an unnamed
connection is opened, replacing any existing unnamed connection.
</P
></DD
><DT
><TT
CLASS="PARAMETER"
>connstr</TT
></DT
><DD
><P
> <SPAN
CLASS="APPLICATION"
>libpq</SPAN
>-style connection info string, for example
<TT
CLASS="LITERAL"
>hostaddr=127.0.0.1 port=5432 dbname=mydb user=postgres
password=mypasswd</TT
>.
For details see <CODE
CLASS="FUNCTION"
>PQconnectdb</CODE
> in
<A
HREF="libpq-connect.html"
>Section 30.1</A
>.
</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN116118"
></A
><H2
>Return Value</H2
><P
> Returns status, which is always <TT
CLASS="LITERAL"
>OK</TT
> (since any error
causes the function to throw an error instead of returning).
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN116122"
></A
><H2
>Notes</H2
><P
> Only superusers may use <CODE
CLASS="FUNCTION"
>dblink_connect</CODE
> to create
non-password-authenticated connections. If non-superusers need this
capability, use <CODE
CLASS="FUNCTION"
>dblink_connect_u</CODE
> instead.
</P
><P
> It is unwise to choose connection names that contain equal signs,
as this opens a risk of confusion with connection info strings
in other <TT
CLASS="FILENAME"
>dblink</TT
> functions.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN116129"
></A
><H2
>Example</H2
><PRE
CLASS="PROGRAMLISTING"
> 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;
</PRE
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