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1<?xml version="1.0" encoding="UTF-8" standalone="no"?>2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>dblink_connect</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="dblink.html" title="F.12. dblink — connect to other PostgreSQL databases" /><link rel="next" href="contrib-dblink-connect-u.html" title="dblink_connect_u" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">dblink_connect</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="dblink.html" title="F.12. dblink — connect to other PostgreSQL databases">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="dblink.html" title="F.12. dblink — connect to other PostgreSQL databases">Up</a></td><th width="60%" align="center">F.12. dblink — connect to other PostgreSQL databases</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="contrib-dblink-connect-u.html" title="dblink_connect_u">Next</a></td></tr></table><hr /></div><div class="refentry" id="CONTRIB-DBLINK-CONNECT"><div class="titlepage"></div><a id="id-1.11.7.22.5.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">dblink_connect</span></h2><p>dblink_connect — opens a persistent connection to a remote database</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">3dblink_connect(text connstr) returns text4dblink_connect(text connname, text connstr) returns text5</pre></div><div class="refsect1" id="id-1.11.7.22.5.5"><h2>Description</h2><p>6    <code class="function">dblink_connect()</code> establishes a connection to a remote7    <span class="productname">PostgreSQL</span> database.  The server and database to8    be contacted are identified through a standard <span class="application">libpq</span>9    connection string.  Optionally, a name can be assigned to the10    connection.  Multiple named connections can be open at once, but11    only one unnamed connection is permitted at a time.  The connection12    will persist until closed or until the database session is ended.13   </p><p>14    The connection string may also be the name of an existing foreign15    server.  It is recommended to use the foreign-data wrapper16    <code class="literal">dblink_fdw</code> when defining the foreign17    server.  See the example below, as well as18    <a class="xref" href="sql-createserver.html" title="CREATE SERVER"><span class="refentrytitle">CREATE SERVER</span></a> and19    <a class="xref" href="sql-createusermapping.html" title="CREATE USER MAPPING"><span class="refentrytitle">CREATE USER MAPPING</span></a>.20   </p></div><div class="refsect1" id="id-1.11.7.22.5.6"><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>connname</code></em></span></dt><dd><p>21       The name to use for this connection; if omitted, an unnamed22       connection is opened, replacing any existing unnamed connection.23      </p></dd><dt><span class="term"><em class="parameter"><code>connstr</code></em></span></dt><dd><p><span class="application">libpq</span>-style connection info string, for example24       <code class="literal">hostaddr=127.0.0.1 port=5432 dbname=mydb user=postgres25       password=mypasswd options=-csearch_path=</code>.26       For details see <a class="xref" href="libpq-connect.html#LIBPQ-CONNSTRING" title="34.1.1. Connection Strings">Section 34.1.1</a>.27       Alternatively, the name of a foreign server.28      </p></dd></dl></div></div><div class="refsect1" id="id-1.11.7.22.5.7"><h2>Return Value</h2><p>29    Returns status, which is always <code class="literal">OK</code> (since any error30    causes the function to throw an error instead of returning).31   </p></div><div class="refsect1" id="id-1.11.7.22.5.8"><h2>Notes</h2><p>32    If untrusted users have access to a database that has not adopted a33    <a class="link" href="ddl-schemas.html#DDL-SCHEMAS-PATTERNS" title="5.9.6. Usage Patterns">secure schema usage pattern</a>,34    begin each session by removing publicly-writable schemas from35    <code class="varname">search_path</code>.  One could, for example,36    add <code class="literal">options=-csearch_path=</code> to37    <em class="parameter"><code>connstr</code></em>.  This consideration is not specific38    to <code class="filename">dblink</code>; it applies to every interface for39    executing arbitrary SQL commands.40   </p><p>41    Only superusers may use <code class="function">dblink_connect</code> to create42    non-password-authenticated and non-GSSAPI-authenticated connections.43    If non-superusers need this capability, use44    <code class="function">dblink_connect_u</code> instead.45   </p><p>46    It is unwise to choose connection names that contain equal signs,47    as this opens a risk of confusion with connection info strings48    in other <code class="filename">dblink</code> functions.49   </p></div><div class="refsect1" id="id-1.11.7.22.5.9"><h2>Examples</h2><pre class="screen">50SELECT dblink_connect('dbname=postgres options=-csearch_path=');51 dblink_connect52----------------53 OK54(1 row)55 56SELECT dblink_connect('myconn', 'dbname=postgres options=-csearch_path=');57 dblink_connect58----------------59 OK60(1 row)61 62-- FOREIGN DATA WRAPPER functionality63-- Note: local connection must require password authentication for this to work properly64--       Otherwise, you will receive the following error from dblink_connect():65--       ERROR:  password is required66--       DETAIL:  Non-superuser cannot connect if the server does not request a password.67--       HINT:  Target server's authentication method must be changed.68 69CREATE SERVER fdtest FOREIGN DATA WRAPPER dblink_fdw OPTIONS (hostaddr '127.0.0.1', dbname 'contrib_regression');70 71CREATE USER regress_dblink_user WITH PASSWORD 'secret';72CREATE USER MAPPING FOR regress_dblink_user SERVER fdtest OPTIONS (user 'regress_dblink_user', password 'secret');73GRANT USAGE ON FOREIGN SERVER fdtest TO regress_dblink_user;74GRANT SELECT ON TABLE foo TO regress_dblink_user;75 76\set ORIGINAL_USER :USER77\c - regress_dblink_user78SELECT dblink_connect('myconn', 'fdtest');79 dblink_connect80----------------81 OK82(1 row)83 84SELECT * FROM dblink('myconn', 'SELECT * FROM foo') AS t(a int, b text, c text[]);85 a  | b |       c86----+---+---------------87  0 | a | {a0,b0,c0}88  1 | b | {a1,b1,c1}89  2 | c | {a2,b2,c2}90  3 | d | {a3,b3,c3}91  4 | e | {a4,b4,c4}92  5 | f | {a5,b5,c5}93  6 | g | {a6,b6,c6}94  7 | h | {a7,b7,c7}95  8 | i | {a8,b8,c8}96  9 | j | {a9,b9,c9}97 10 | k | {a10,b10,c10}98(11 rows)99 100\c - :ORIGINAL_USER101REVOKE USAGE ON FOREIGN SERVER fdtest FROM regress_dblink_user;102REVOKE SELECT ON TABLE foo FROM regress_dblink_user;103DROP USER MAPPING FOR regress_dblink_user SERVER fdtest;104DROP USER regress_dblink_user;105DROP SERVER fdtest;106</pre></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="dblink.html" title="F.12. dblink — connect to other PostgreSQL databases">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="dblink.html" title="F.12. dblink — connect to other PostgreSQL databases">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="contrib-dblink-connect-u.html" title="dblink_connect_u">Next</a></td></tr><tr><td width="40%" align="left" valign="top">F.12. dblink — connect to other PostgreSQL databases </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 16.3 Documentation">Home</a></td><td width="40%" align="right" valign="top"> dblink_connect_u</td></tr></table></div></body></html>