Accept postgres:// URIs in libpq connection functions

postgres:// URIs are an attempt to "stop the bleeding" in this general
area that has been said to occur due to external projects adopting their
own syntaxes.  The syntaxes supported by this patch:

 postgres://[user[:pwd]@][unix-socket][:port[/dbname]][?param1=value1&...]
 postgres://[user[:pwd]@][net-location][:port][/dbname][?param1=value1&...]

should be enough to cover most interesting cases without having to
resort to "param=value" pairs, but those are provided for the cases that
need them regardless.

libpq documentation has been shuffled around a bit, to avoid stuffing
all the format details into the PQconnectdbParams description, which was
already a bit overwhelming.  The list of keywords has moved to its own
subsection, and the details on the URI format live in another subsection.

This includes a simple test program, as requested in discussion, to
ensure that interesting corner cases continue to work appropriately in
the future.

Author: Alexander Shulgin
Some tweaking by Álvaro Herrera, Greg Smith, Daniel Farina, Peter Eisentraut
Reviewed by Robert Haas, Alexey Klyukin (offlist), Heikki Linnakangas,
Marko Kreen, and others

Oh, it also supports postgresql:// but that's probably just an accident.

2 files changed, 641 insertions, 534 deletions

diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 0ec501e5bda..8a820ac0074 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -117,9 +117,15 @@ PGconn *PQconnectdbParams(const char * const *keywords,
       </para>
 
       <para>
+       The currently recognized parameter key words are listed in
+       <xref linkend="libpq-paramkeywords">.
+      </para>
+
+      <para>
        When <literal>expand_dbname</literal> is non-zero, the
        <parameter>dbname</parameter> key word value is allowed to be recognized
-       as a <parameter>conninfo</parameter> string. See below for details.
+       as a connection string. More details on the possible formats appear in
+       <xref linkend="libpq-connstring">.
       </para>
 
       <para>
@@ -130,507 +136,6 @@ PGconn *PQconnectdbParams(const char * const *keywords,
       </para>
 
       <para>
-       The currently recognized parameter key words are:
-
-       <variablelist>
-        <varlistentry id="libpq-connect-host" xreflabel="host">
-         <term><literal>host</literal></term>
-         <listitem>
-          <para>
-           Name of host to connect to.<indexterm><primary>host name</></>
-           If this begins with a slash, it specifies Unix-domain
-           communication rather than TCP/IP communication; the value is the
-           name of the directory in which the socket file is stored.  The
-           default behavior when <literal>host</literal> is not specified
-           is to connect to a Unix-domain
-           socket<indexterm><primary>Unix domain socket</></> in
-           <filename>/tmp</filename> (or whatever socket directory was specified
-           when <productname>PostgreSQL</> was built). On machines without
-           Unix-domain sockets, the default is to connect to <literal>localhost</>.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-hostaddr" xreflabel="hostaddr">
-         <term><literal>hostaddr</literal></term>
-         <listitem>
-          <para>
-           Numeric IP address of host to connect to.  This should be in the
-           standard IPv4 address format, e.g., <literal>172.28.40.9</>.  If
-           your machine supports IPv6, you can also use those addresses.
-           TCP/IP communication is
-           always used when a nonempty string is specified for this parameter.
-          </para>
-
-          <para>
-           Using <literal>hostaddr</> instead of <literal>host</> allows the
-           application to avoid a host name look-up, which might be important
-           in applications with time constraints. However, a host name is
-           required for Kerberos, GSSAPI, or SSPI authentication
-           methods, as well as for <literal>verify-full</> SSL
-           certificate verification.  The following rules are used:
-           <itemizedlist>
-            <listitem>
-             <para>
-              If <literal>host</> is specified without <literal>hostaddr</>,
-              a host name lookup occurs.
-             </para>
-            </listitem>
-            <listitem>
-             <para>
-              If <literal>hostaddr</> is specified without <literal>host</>,
-              the value for <literal>hostaddr</> gives the server network address.
-              The connection attempt will fail if the authentication
-              method requires a host name.
-             </para>
-            </listitem>
-            <listitem>
-             <para>
-              If both <literal>host</> and <literal>hostaddr</> are specified,
-              the value for <literal>hostaddr</> gives the server network address.
-              The value for <literal>host</> is ignored unless the
-              authentication method requires it, in which case it will be
-              used as the host name.
-             </para>
-            </listitem>
-           </itemizedlist>
-           Note that authentication is likely to fail if <literal>host</>
-           is not the name of the server at network address <literal>hostaddr</>.
-           Also, note that <literal>host</> rather than <literal>hostaddr</>
-           is used to identify the connection in <filename>~/.pgpass</> (see
-           <xref linkend="libpq-pgpass">).
-          </para>
-
-          <para>
-           Without either a host name or host address,
-           <application>libpq</application> will connect using a
-           local Unix-domain socket; or on machines without Unix-domain
-           sockets, it will attempt to connect to <literal>localhost</>.
-          </para>
-          </listitem>
-         </varlistentry>
-
-         <varlistentry id="libpq-connect-port" xreflabel="port">
-          <term><literal>port</literal></term>
-          <listitem>
-          <para>
-           Port number to connect to at the server host, or socket file
-           name extension for Unix-domain
-           connections.<indexterm><primary>port</></>
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-dbname" xreflabel="dbname">
-         <term><literal>dbname</literal></term>
-         <listitem>
-         <para>
-          The database name.  Defaults to be the same as the user name.
-         </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-user" xreflabel="user">
-         <term><literal>user</literal></term>
-         <listitem>
-         <para>
-          <productname>PostgreSQL</productname> user name to connect as.
-          Defaults to be the same as the operating system name of the user
-          running the application.
-         </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-password" xreflabel="password">
-         <term><literal>password</literal></term>
-         <listitem>
-         <para>
-          Password to be used if the server demands password authentication.
-         </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-connect-timeout" xreflabel="connect_timeout">
-         <term><literal>connect_timeout</literal></term>
-         <listitem>
-         <para>
-          Maximum wait for connection, in seconds (write as a decimal integer
-          string). Zero or not specified means wait indefinitely.  It is not
-          recommended to use a timeout of less than 2 seconds.
-         </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-client-encoding" xreflabel="client_encoding">
-         <term><literal>client_encoding</literal></term>
-         <listitem>
-         <para>
-          This sets the <varname>client_encoding</varname>
-          configuration parameter for this connection.  In addition to
-          the values accepted by the corresponding server option, you
-          can use <literal>auto</literal> to determine the right
-          encoding from the current locale in the client
-          (<envar>LC_CTYPE</envar> environment variable on Unix
-          systems).
-         </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-options" xreflabel="options">
-         <term><literal>options</literal></term>
-         <listitem>
-          <para>
-           Adds command-line options to send to the server at run-time.
-           For example, setting this to <literal>-c geqo=off</> sets the
-           session's value of the <varname>geqo</> parameter to
-           <literal>off</>.  For a detailed discussion of the available
-           options, consult <xref linkend="runtime-config">.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-application-name" xreflabel="application_name">
-         <term><literal>application_name</literal></term>
-         <listitem>
-          <para>
-           Specifies a value for the <xref linkend="guc-application-name">
-           configuration parameter.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-fallback-application-name" xreflabel="fallback_application_name">
-         <term><literal>fallback_application_name</literal></term>
-         <listitem>
-          <para>
-           Specifies a fallback value for the <xref
-           linkend="guc-application-name"> configuration parameter.
-           This value will be used if no value has been given for
-           <literal>application_name</> via a connection parameter or the
-           <envar>PGAPPNAME</envar> environment variable.  Specifying
-           a fallback name is useful in generic utility programs that
-           wish to set a default application name but allow it to be
-           overridden by the user.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-keepalives" xreflabel="keepalives">
-         <term><literal>keepalives</literal></term>
-         <listitem>
-          <para>
-           Controls whether client-side TCP keepalives are used. The default
-           value is 1, meaning on, but you can change this to 0, meaning off,
-           if keepalives are not wanted.  This parameter is ignored for
-           connections made via a Unix-domain socket.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-keepalives-idle" xreflabel="keepalives_idle">
-         <term><literal>keepalives_idle</literal></term>
-         <listitem>
-          <para>
-           Controls the number of seconds of inactivity after which TCP should
-           send a keepalive message to the server.  A value of zero uses the
-           system default. This parameter is ignored for connections made via a
-           Unix-domain socket, or if keepalives are disabled. It is only supported
-           on systems where the <symbol>TCP_KEEPIDLE</> or <symbol>TCP_KEEPALIVE</>
-           socket option is available, and on Windows; on other systems, it has no
-           effect.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-keepalives-interval" xreflabel="keepalives_interval">
-         <term><literal>keepalives_interval</literal></term>
-         <listitem>
-          <para>
-           Controls the number of seconds after which a TCP keepalive message
-           that is not acknowledged by the server should be retransmitted.  A
-           value of zero uses the system default. This parameter is ignored for
-           connections made via a Unix-domain socket, or if keepalives are disabled.
-           It is only supported on systems where the <symbol>TCP_KEEPINTVL</>
-           socket option is available, and on Windows; on other systems, it has no
-           effect.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-keepalives-count" xreflabel="keepalives_count">
-         <term><literal>keepalives_count</literal></term>
-         <listitem>
-          <para>
-           Controls the number of TCP keepalives that can be lost before the
-           client's connection to the server is considered dead.  A value of
-           zero uses the system default. This parameter is ignored for
-           connections made via a Unix-domain socket, or if keepalives are disabled.
-           It is only supported on systems where the <symbol>TCP_KEEPCNT</>
-           socket option is available; on other systems, it has no effect.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-tty" xreflabel="tty">
-         <term><literal>tty</literal></term>
-         <listitem>
-         <para>
-          Ignored (formerly, this specified where to send server debug output).
-         </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-sslmode" xreflabel="sslmode">
-         <term><literal>sslmode</literal></term>
-         <listitem>
-          <para>
-           This option determines whether or with what priority a secure
-           <acronym>SSL</> TCP/IP connection will be negotiated with the
-           server. There are six modes:
-
-           <variablelist>
-            <varlistentry>
-             <term><literal>disable</literal></term>
-             <listitem>
-              <para>
-               only try a non-<acronym>SSL</> connection
-              </para>
-             </listitem>
-            </varlistentry>
-
-            <varlistentry>
-             <term><literal>allow</literal></term>
-             <listitem>
-              <para>
-               first try a non-<acronym>SSL</> connection; if that
-               fails, try an <acronym>SSL</> connection
-              </para>
-             </listitem>
-            </varlistentry>
-
-            <varlistentry>
-             <term><literal>prefer</literal> (default)</term>
-             <listitem>
-              <para>
-               first try an <acronym>SSL</> connection; if that fails,
-               try a non-<acronym>SSL</> connection
-              </para>
-             </listitem>
-            </varlistentry>
-
-            <varlistentry>
-             <term><literal>require</literal></term>
-             <listitem>
-              <para>
-               only try an <acronym>SSL</> connection. If a root CA
-               file is present, verify the certificate in the same way as
-               if <literal>verify-ca</literal> was specified
-              </para>
-             </listitem>
-            </varlistentry>
-
-            <varlistentry>
-             <term><literal>verify-ca</literal></term>
-             <listitem>
-              <para>
-               only try an <acronym>SSL</> connection, and verify that
-               the server certificate is issued by a trusted
-               certificate authority (<acronym>CA</>)
-              </para>
-             </listitem>
-            </varlistentry>
-
-            <varlistentry>
-             <term><literal>verify-full</literal></term>
-             <listitem>
-              <para>
-               only try an <acronym>SSL</> connection, verify that the
-               server certificate is issued by a
-               trusted <acronym>CA</> and that the server host name
-               matches that in the certificate
-              </para>
-             </listitem>
-            </varlistentry>
-           </variablelist>
-
-           See <xref linkend="libpq-ssl"> for a detailed description of how
-           these options work.
-          </para>
-
-          <para>
-           <literal>sslmode</> is ignored for Unix domain socket
-           communication.
-           If <productname>PostgreSQL</> is compiled without SSL support,
-           using options <literal>require</>, <literal>verify-ca</>, or
-           <literal>verify-full</> will cause an error, while
-           options <literal>allow</> and <literal>prefer</> will be
-           accepted but <application>libpq</> will not actually attempt
-           an <acronym>SSL</>
-           connection.<indexterm><primary>SSL</><secondary
-           sortas="libpq">with libpq</></indexterm>
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-requiressl" xreflabel="requiressl">
-         <term><literal>requiressl</literal></term>
-         <listitem>
-          <para>
-           This option is deprecated in favor of the <literal>sslmode</>
-           setting.
-          </para>
-
-          <para>
-           If set to 1, an <acronym>SSL</acronym> connection to the server
-           is required (this is equivalent to <literal>sslmode</>
-           <literal>require</>).  <application>libpq</> will then refuse
-           to connect if the server does not accept an
-           <acronym>SSL</acronym> connection.  If set to 0 (default),
-           <application>libpq</> will negotiate the connection type with
-           the server (equivalent to <literal>sslmode</>
-           <literal>prefer</>).  This option is only available if
-           <productname>PostgreSQL</> is compiled with SSL support.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-sslcompression" xreflabel="sslcompression">
-         <term><literal>sslcompression</literal></term>
-         <listitem>
-          <para>
-           If set to 1 (default), data sent over SSL connections will be
-           compressed (this requires <productname>OpenSSL</> version
-           0.9.8 or later).
-           If set to 0, compression will be disabled (this requires
-           <productname>OpenSSL</> 1.0.0 or later).
-           This parameter is ignored if a connection without SSL is made,
-           or if the version of <productname>OpenSSL</> used does not support
-           it.
-          </para>
-          <para>
-           Compression uses CPU time, but can improve throughput if
-           the network is the bottleneck.
-           Disabling compression can improve response time and throughput
-           if CPU performance is the limiting factor.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-sslcert" xreflabel="sslcert">
-         <term><literal>sslcert</literal></term>
-         <listitem>
-          <para>
-           This parameter specifies the file name of the client SSL
-           certificate, replacing the default
-           <filename>~/.postgresql/postgresql.crt</>.
-           This parameter is ignored if an SSL connection is not made.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-sslkey" xreflabel="sslkey">
-         <term><literal>sslkey</literal></term>
-         <listitem>
-          <para>
-           This parameter specifies the location for the secret key used for
-           the client certificate. It can either specify a file name that will
-           be used instead of the default
-           <filename>~/.postgresql/postgresql.key</>, or it can specify a key
-           obtained from an external <quote>engine</> (engines are
-           <productname>OpenSSL</> loadable modules).  An external engine
-           specification should consist of a colon-separated engine name and
-           an engine-specific key identifier.  This parameter is ignored if an
-           SSL connection is not made.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-sslrootcert" xreflabel="sslrootcert">
-         <term><literal>sslrootcert</literal></term>
-         <listitem>
-          <para>
-           This parameter specifies the name of a file containing SSL
-           certificate authority (<acronym>CA</>) certificate(s).
-           If the file exists, the server's certificate will be verified
-           to be signed by one of these authorities.  The default is
-           <filename>~/.postgresql/root.crt</>.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-sslcrl" xreflabel="sslcrl">
-         <term><literal>sslcrl</literal></term>
-         <listitem>
-          <para>
-           This parameter specifies the file name of the SSL certificate
-           revocation list (CRL).  Certificates listed in this file, if it
-           exists, will be rejected while attempting to authenticate the
-           server's certificate.  The default is
-           <filename>~/.postgresql/root.crl</>.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-requirepeer" xreflabel="requirepeer">
-         <term><literal>requirepeer</literal></term>
-         <listitem>
-          <para>
-           This parameter specifies the operating-system user name of the
-           server, for example <literal>requirepeer=postgres</literal>.
-           When making a Unix-domain socket connection, if this
-           parameter is set, the client checks at the beginning of the
-           connection that the server process is running under the specified
-           user name; if it is not, the connection is aborted with an error.
-           This parameter can be used to provide server authentication similar
-           to that available with SSL certificates on TCP/IP connections.
-           (Note that if the Unix-domain socket is in
-           <filename>/tmp</filename> or another publicly writable location,
-           any user could start a server listening there.  Use this parameter
-           to ensure that you are connected to a server run by a trusted user.)
-           This option is only supported on platforms for which the
-           <literal>peer</> authentication method is implemented; see
-           <xref linkend="auth-peer">.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-krbsrvname" xreflabel="krbsrvname">
-         <term><literal>krbsrvname</literal></term>
-         <listitem>
-          <para>
-           Kerberos service name to use when authenticating with Kerberos 5
-           or GSSAPI.
-           This must match the service name specified in the server
-           configuration for Kerberos authentication to succeed. (See also
-           <xref linkend="kerberos-auth"> and <xref linkend="gssapi-auth">.)
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-gsslib" xreflabel="gsslib">
-         <term><literal>gsslib</literal></term>
-         <listitem>
-          <para>
-           GSS library to use for GSSAPI authentication. Only used on Windows.
-           Set to <literal>gssapi</literal> to force libpq to use the GSSAPI
-           library for authentication instead of the default SSPI.
-          </para>
-         </listitem>
-        </varlistentry>
-
-        <varlistentry id="libpq-connect-service" xreflabel="service">
-         <term><literal>service</literal></term>
-         <listitem>
-          <para>
-           Service name to use for additional parameters.  It specifies a service
-           name in <filename>pg_service.conf</filename> that holds additional connection parameters.
-           This allows applications to specify only a service name so connection parameters
-           can be centrally maintained. See <xref linkend="libpq-pgservice">.
-          </para>
-         </listitem>
-        </varlistentry>
-       </variablelist>
-
        If  any  parameter is unspecified, then the corresponding
        environment variable (see <xref linkend="libpq-envars">)
        is checked. If the  environment  variable is not set either,
@@ -638,20 +143,11 @@ PGconn *PQconnectdbParams(const char * const *keywords,
       </para>
 
       <para>
-        If <literal>expand_dbname</literal> is non-zero and
-        <parameter>dbname</parameter> contains an <symbol>=</symbol> sign, it
-        is taken as a <parameter>conninfo</parameter> string in exactly the same way as
-        if it had been passed to <function>PQconnectdb</function>(see below). Previously
-        processed key words will be overridden by key words in the
-        <parameter>conninfo</parameter> string.
-      </para>
-
-      <para>
-        In general key words are processed from the beginning of these arrays in index
-        order. The effect of this is that when key words are repeated, the last processed
-        value is retained. Therefore, through careful placement of the
-        <parameter>dbname</parameter> key word, it is possible to determine what may
-        be overridden by a <parameter>conninfo</parameter> string, and what may not.
+       In general key words are processed from the beginning of these arrays in index
+       order. The effect of this is that when key words are repeated, the last processed
+       value is retained. Therefore, through careful placement of the
+       <parameter>dbname</parameter> key word, it is possible to determine what may
+       be overridden by a <parameter>conninfo</parameter> string, and what may not.
       </para>
 
      </listitem>
@@ -675,19 +171,13 @@ PGconn *PQconnectdb(const char *conninfo);
 
       <para>
        The passed string can be empty to use all default parameters, or it can
-       contain one or more parameter settings separated by whitespace.
-       Each parameter setting is in the form <literal>keyword = value</literal>.
-       Spaces around the equal sign are optional. To write an empty value,
-       or a value containing spaces, surround it with single quotes, e.g.,
-       <literal>keyword = 'a value'</literal>. Single quotes and backslashes
-       within the value must be escaped with a backslash, i.e.,
-       <literal>\'</literal> and <literal>\\</literal>.
-      </para>
+       contain one or more parameter settings separated by whitespace,
+       or it can contain a <acronym>URI</acronym>.
+       See <xref linkend="libpq-connstring"> for details.
+     </para>
 
-      <para>
-       The currently recognized parameter key words are the same as above.
-      </para>
-     </listitem>
+
+    </listitem>
     </varlistentry>
 
     <varlistentry id="libpq-pqsetdblogin">
@@ -714,10 +204,11 @@ PGconn *PQsetdbLogin(const char *pghost,
       </para>
 
       <para>
-        If the <parameter>dbName</parameter> contains an <symbol>=</symbol> sign, it
+        If the <parameter>dbName</parameter> contains
+        an <symbol>=</symbol> sign or has a valid connection <acronym>URI</acronym> prefix, it
         is taken as a <parameter>conninfo</parameter> string in exactly the same way as
         if it had been passed to <function>PQconnectdb</function>, and the remaining
-        parameters are then applied as above.
+        parameters are then applied as specified for <function>PQconnectdbParams</>.
       </para>
      </listitem>
     </varlistentry>
@@ -795,7 +286,7 @@ PostgresPollingStatusType PQconnectPoll(PGconn *conn);
          <para>
           The <literal>hostaddr</> and <literal>host</> parameters are used appropriately to ensure that
           name and reverse name queries are not made. See the documentation of
-          these parameters under <function>PQconnectdbParams</function> above for details.
+          these parameters in <xref linkend="libpq-paramkeywords"> for details.
          </para>
         </listitem>
 
@@ -1219,6 +710,617 @@ PGPing PQping(const char *conninfo);
 
    </variablelist>
   </para>
+
+  <sect2 id="libpq-paramkeywords">
+   <title>Parameter Key Words</title>
+
+   <para>
+    The currently recognized parameter key words are:
+
+    <variablelist>
+     <varlistentry id="libpq-connect-host" xreflabel="host">
+      <term><literal>host</literal></term>
+      <listitem>
+       <para>
+        Name of host to connect to.<indexterm><primary>host name</></>
+        If this begins with a slash, it specifies Unix-domain
+        communication rather than TCP/IP communication; the value is the
+        name of the directory in which the socket file is stored.  The
+        default behavior when <literal>host</literal> is not specified
+        is to connect to a Unix-domain
+        socket<indexterm><primary>Unix domain socket</></> in
+        <filename>/tmp</filename> (or whatever socket directory was specified
+        when <productname>PostgreSQL</> was built). On machines without
+        Unix-domain sockets, the default is to connect to <literal>localhost</>.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-hostaddr" xreflabel="hostaddr">
+      <term><literal>hostaddr</literal></term>
+      <listitem>
+       <para>
+        Numeric IP address of host to connect to.  This should be in the
+        standard IPv4 address format, e.g., <literal>172.28.40.9</>.  If
+        your machine supports IPv6, you can also use those addresses.
+        TCP/IP communication is
+        always used when a nonempty string is specified for this parameter.
+       </para>
+
+       <para>
+        Using <literal>hostaddr</> instead of <literal>host</> allows the
+        application to avoid a host name look-up, which might be important
+        in applications with time constraints. However, a host name is
+        required for Kerberos, GSSAPI, or SSPI authentication
+        methods, as well as for <literal>verify-full</> SSL
+        certificate verification.  The following rules are used:
+        <itemizedlist>
+         <listitem>
+          <para>
+           If <literal>host</> is specified without <literal>hostaddr</>,
+           a host name lookup occurs.
+          </para>
+         </listitem>
+         <listitem>
+          <para>
+           If <literal>hostaddr</> is specified without <literal>host</>,
+           the value for <literal>hostaddr</> gives the server network address.
+           The connection attempt will fail if the authentication
+           method requires a host name.
+          </para>
+         </listitem>
+         <listitem>
+          <para>
+           If both <literal>host</> and <literal>hostaddr</> are specified,
+           the value for <literal>hostaddr</> gives the server network address.
+           The value for <literal>host</> is ignored unless the
+           authentication method requires it, in which case it will be
+           used as the host name.
+          </para>
+         </listitem>
+        </itemizedlist>
+        Note that authentication is likely to fail if <literal>host</>
+        is not the name of the server at network address <literal>hostaddr</>.
+        Also, note that <literal>host</> rather than <literal>hostaddr</>
+        is used to identify the connection in <filename>~/.pgpass</> (see
+        <xref linkend="libpq-pgpass">).
+       </para>
+
+       <para>
+        Without either a host name or host address,
+        <application>libpq</application> will connect using a
+        local Unix-domain socket; or on machines without Unix-domain
+        sockets, it will attempt to connect to <literal>localhost</>.
+       </para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry id="libpq-connect-port" xreflabel="port">
+       <term><literal>port</literal></term>
+       <listitem>
+       <para>
+        Port number to connect to at the server host, or socket file
+        name extension for Unix-domain
+        connections.<indexterm><primary>port</></>
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-dbname" xreflabel="dbname">
+      <term><literal>dbname</literal></term>
+      <listitem>
+      <para>
+       The database name.  Defaults to be the same as the user name.
+       In certain contexts, the value is checked for extended
+       formats; see <xref linkend="libpq-connstring"> for more details on
+       those.
+      </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-user" xreflabel="user">
+      <term><literal>user</literal></term>
+      <listitem>
+      <para>
+       <productname>PostgreSQL</productname> user name to connect as.
+       Defaults to be the same as the operating system name of the user
+       running the application.
+      </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-password" xreflabel="password">
+      <term><literal>password</literal></term>
+      <listitem>
+      <para>
+       Password to be used if the server demands password authentication.
+      </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-connect-timeout" xreflabel="connect_timeout">
+      <term><literal>connect_timeout</literal></term>
+      <listitem>
+      <para>
+       Maximum wait for connection, in seconds (write as a decimal integer
+       string). Zero or not specified means wait indefinitely.  It is not
+       recommended to use a timeout of less than 2 seconds.
+      </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-client-encoding" xreflabel="client_encoding">
+      <term><literal>client_encoding</literal></term>
+      <listitem>
+      <para>
+       This sets the <varname>client_encoding</varname>
+       configuration parameter for this connection.  In addition to
+       the values accepted by the corresponding server option, you
+       can use <literal>auto</literal> to determine the right
+       encoding from the current locale in the client
+       (<envar>LC_CTYPE</envar> environment variable on Unix
+       systems).
+      </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-options" xreflabel="options">
+      <term><literal>options</literal></term>
+      <listitem>
+       <para>
+        Adds command-line options to send to the server at run-time.
+        For example, setting this to <literal>-c geqo=off</> sets the
+        session's value of the <varname>geqo</> parameter to
+        <literal>off</>.  For a detailed discussion of the available
+        options, consult <xref linkend="runtime-config">.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-application-name" xreflabel="application_name">
+      <term><literal>application_name</literal></term>
+      <listitem>
+       <para>
+        Specifies a value for the <xref linkend="guc-application-name">
+        configuration parameter.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-fallback-application-name" xreflabel="fallback_application_name">
+      <term><literal>fallback_application_name</literal></term>
+      <listitem>
+       <para>
+        Specifies a fallback value for the <xref
+        linkend="guc-application-name"> configuration parameter.
+        This value will be used if no value has been given for
+        <literal>application_name</> via a connection parameter or the
+        <envar>PGAPPNAME</envar> environment variable.  Specifying
+        a fallback name is useful in generic utility programs that
+        wish to set a default application name but allow it to be
+        overridden by the user.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-keepalives" xreflabel="keepalives">
+      <term><literal>keepalives</literal></term>
+      <listitem>
+       <para>
+        Controls whether client-side TCP keepalives are used. The default
+        value is 1, meaning on, but you can change this to 0, meaning off,
+        if keepalives are not wanted.  This parameter is ignored for
+        connections made via a Unix-domain socket.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-keepalives-idle" xreflabel="keepalives_idle">
+      <term><literal>keepalives_idle</literal></term>
+      <listitem>
+       <para>
+        Controls the number of seconds of inactivity after which TCP should
+        send a keepalive message to the server.  A value of zero uses the
+        system default. This parameter is ignored for connections made via a
+        Unix-domain socket, or if keepalives are disabled. It is only supported
+        on systems where the <symbol>TCP_KEEPIDLE</> or <symbol>TCP_KEEPALIVE</>
+        socket option is available, and on Windows; on other systems, it has no
+        effect.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-keepalives-interval" xreflabel="keepalives_interval">
+      <term><literal>keepalives_interval</literal></term>
+      <listitem>
+       <para>
+        Controls the number of seconds after which a TCP keepalive message
+        that is not acknowledged by the server should be retransmitted.  A
+        value of zero uses the system default. This parameter is ignored for
+        connections made via a Unix-domain socket, or if keepalives are disabled.
+        It is only supported on systems where the <symbol>TCP_KEEPINTVL</>
+        socket option is available, and on Windows; on other systems, it has no
+        effect.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-keepalives-count" xreflabel="keepalives_count">
+      <term><literal>keepalives_count</literal></term>
+      <listitem>
+       <para>
+        Controls the number of TCP keepalives that can be lost before the
+        client's connection to the server is considered dead.  A value of
+        zero uses the system default. This parameter is ignored for
+        connections made via a Unix-domain socket, or if keepalives are disabled.
+        It is only supported on systems where the <symbol>TCP_KEEPCNT</>
+        socket option is available; on other systems, it has no effect.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-tty" xreflabel="tty">
+      <term><literal>tty</literal></term>
+      <listitem>
+      <para>
+       Ignored (formerly, this specified where to send server debug output).
+      </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-sslmode" xreflabel="sslmode">
+      <term><literal>sslmode</literal></term>
+      <listitem>
+       <para>
+        This option determines whether or with what priority a secure
+        <acronym>SSL</> TCP/IP connection will be negotiated with the
+        server. There are six modes:
+
+        <variablelist>
+         <varlistentry>
+          <term><literal>disable</literal></term>
+          <listitem>
+           <para>
+            only try a non-<acronym>SSL</> connection
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>allow</literal></term>
+          <listitem>
+           <para>
+            first try a non-<acronym>SSL</> connection; if that
+            fails, try an <acronym>SSL</> connection
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>prefer</literal> (default)</term>
+          <listitem>
+           <para>
+            first try an <acronym>SSL</> connection; if that fails,
+            try a non-<acronym>SSL</> connection
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>require</literal></term>
+          <listitem>
+           <para>
+            only try an <acronym>SSL</> connection. If a root CA
+            file is present, verify the certificate in the same way as
+            if <literal>verify-ca</literal> was specified
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>verify-ca</literal></term>
+          <listitem>
+           <para>
+            only try an <acronym>SSL</> connection, and verify that
+            the server certificate is issued by a trusted
+            certificate authority (<acronym>CA</>)
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>verify-full</literal></term>
+          <listitem>
+           <para>
+            only try an <acronym>SSL</> connection, verify that the
+            server certificate is issued by a
+            trusted <acronym>CA</> and that the server host name
+            matches that in the certificate
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+
+        See <xref linkend="libpq-ssl"> for a detailed description of how
+        these options work.
+       </para>
+
+       <para>
+        <literal>sslmode</> is ignored for Unix domain socket
+        communication.
+        If <productname>PostgreSQL</> is compiled without SSL support,
+        using options <literal>require</>, <literal>verify-ca</>, or
+        <literal>verify-full</> will cause an error, while
+        options <literal>allow</> and <literal>prefer</> will be
+        accepted but <application>libpq</> will not actually attempt
+        an <acronym>SSL</>
+        connection.<indexterm><primary>SSL</><secondary
+        sortas="libpq">with libpq</></indexterm>
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-requiressl" xreflabel="requiressl">
+      <term><literal>requiressl</literal></term>
+      <listitem>
+       <para>
+        This option is deprecated in favor of the <literal>sslmode</>
+        setting.
+       </para>
+
+       <para>
+        If set to 1, an <acronym>SSL</acronym> connection to the server
+        is required (this is equivalent to <literal>sslmode</>
+        <literal>require</>).  <application>libpq</> will then refuse
+        to connect if the server does not accept an
+        <acronym>SSL</acronym> connection.  If set to 0 (default),
+        <application>libpq</> will negotiate the connection type with
+        the server (equivalent to <literal>sslmode</>
+        <literal>prefer</>).  This option is only available if
+        <productname>PostgreSQL</> is compiled with SSL support.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-sslcompression" xreflabel="sslcompression">
+      <term><literal>sslcompression</literal></term>
+      <listitem>
+       <para>
+        If set to 1 (default), data sent over SSL connections will be
+        compressed (this requires <productname>OpenSSL</> version
+        0.9.8 or later).
+        If set to 0, compression will be disabled (this requires
+        <productname>OpenSSL</> 1.0.0 or later).
+        This parameter is ignored if a connection without SSL is made,
+        or if the version of <productname>OpenSSL</> used does not support
+        it.
+       </para>
+       <para>
+        Compression uses CPU time, but can improve throughput if
+        the network is the bottleneck.
+        Disabling compression can improve response time and throughput
+        if CPU performance is the limiting factor.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-sslcert" xreflabel="sslcert">
+      <term><literal>sslcert</literal></term>
+      <listitem>
+       <para>
+        This parameter specifies the file name of the client SSL
+        certificate, replacing the default
+        <filename>~/.postgresql/postgresql.crt</>.
+        This parameter is ignored if an SSL connection is not made.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-sslkey" xreflabel="sslkey">
+      <term><literal>sslkey</literal></term>
+      <listitem>
+       <para>
+        This parameter specifies the location for the secret key used for
+        the client certificate. It can either specify a file name that will
+        be used instead of the default
+        <filename>~/.postgresql/postgresql.key</>, or it can specify a key
+        obtained from an external <quote>engine</> (engines are
+        <productname>OpenSSL</> loadable modules).  An external engine
+        specification should consist of a colon-separated engine name and
+        an engine-specific key identifier.  This parameter is ignored if an
+        SSL connection is not made.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-sslrootcert" xreflabel="sslrootcert">
+      <term><literal>sslrootcert</literal></term>
+      <listitem>
+       <para>
+        This parameter specifies the name of a file containing SSL
+        certificate authority (<acronym>CA</>) certificate(s).
+        If the file exists, the server's certificate will be verified
+        to be signed by one of these authorities.  The default is
+        <filename>~/.postgresql/root.crt</>.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-sslcrl" xreflabel="sslcrl">
+      <term><literal>sslcrl</literal></term>
+      <listitem>
+       <para>
+        This parameter specifies the file name of the SSL certificate
+        revocation list (CRL).  Certificates listed in this file, if it
+        exists, will be rejected while attempting to authenticate the
+        server's certificate.  The default is
+        <filename>~/.postgresql/root.crl</>.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-requirepeer" xreflabel="requirepeer">
+      <term><literal>requirepeer</literal></term>
+      <listitem>
+       <para>
+        This parameter specifies the operating-system user name of the
+        server, for example <literal>requirepeer=postgres</literal>.
+        When making a Unix-domain socket connection, if this
+        parameter is set, the client checks at the beginning of the
+        connection that the server process is running under the specified
+        user name; if it is not, the connection is aborted with an error.
+        This parameter can be used to provide server authentication similar
+        to that available with SSL certificates on TCP/IP connections.
+        (Note that if the Unix-domain socket is in
+        <filename>/tmp</filename> or another publicly writable location,
+        any user could start a server listening there.  Use this parameter
+        to ensure that you are connected to a server run by a trusted user.)
+        This option is only supported on platforms for which the
+        <literal>peer</> authentication method is implemented; see
+        <xref linkend="auth-peer">.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-krbsrvname" xreflabel="krbsrvname">
+      <term><literal>krbsrvname</literal></term>
+      <listitem>
+       <para>
+        Kerberos service name to use when authenticating with Kerberos 5
+        or GSSAPI.
+        This must match the service name specified in the server
+        configuration for Kerberos authentication to succeed. (See also
+        <xref linkend="kerberos-auth"> and <xref linkend="gssapi-auth">.)
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-gsslib" xreflabel="gsslib">
+      <term><literal>gsslib</literal></term>
+      <listitem>
+       <para>
+        GSS library to use for GSSAPI authentication. Only used on Windows.
+        Set to <literal>gssapi</literal> to force libpq to use the GSSAPI
+        library for authentication instead of the default SSPI.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-connect-service" xreflabel="service">
+      <term><literal>service</literal></term>
+      <listitem>
+       <para>
+        Service name to use for additional parameters.  It specifies a service
+        name in <filename>pg_service.conf</filename> that holds additional connection parameters.
+        This allows applications to specify only a service name so connection parameters
+        can be centrally maintained. See <xref linkend="libpq-pgservice">.
+       </para>
+      </listitem>
+     </varlistentry>
+    </variablelist>
+   </para>
+  </sect2>
+
+  <sect2 id="libpq-connstring">
+   <title>Connection Strings</title>
+
+   <indexterm zone="libpq-connstring">
+    <primary><literal>conninfo</literal></primary>
+   </indexterm>
+
+   <indexterm zone="libpq-connstring">
+    <primary><literal>URI</literal></primary>
+   </indexterm>
+
+   <para>
+    Several <application>libpq</> functions parse a user-specified string to obtain
+    connection parameters.  There are two accepted formats for these strings:
+    plain <literal>keyword = value</literal> strings, and URIs.
+   </para>
+
+   <para>
+    In the first format, each parameter setting is in the form
+    <literal>keyword = value</literal>.  Spaces around the equal sign are
+    optional. To write an empty value, or a value containing spaces, surround it
+    with single quotes, e.g., <literal>keyword = 'a value'</literal>. Single
+    quotes and backslashes within
+    the value must be escaped with a backslash, i.e., <literal>\'</literal> and
+    <literal>\\</literal>.
+   </para>
+
+   <para>
+    The currently recognized parameter key words are listed in
+    <xref linkend="libpq-paramkeywords">.
+   </para>
+
+   <para>
+   The general form for connection <acronym>URI</acronym> is the
+   following:
+<synopsis>
+postgresql://[user[:password]@][unix-socket][:port[/dbname]][?param1=value1&amp;...]
+postgresql://[user[:password]@][net-location][:port][/dbname][?param1=value1&amp;...]
+</synopsis>
+   </para>
+
+   <para>
+    The <acronym>URI</acronym> designator can be either
+    <literal>postgresql://</literal> or <literal>postgres://</literal> and
+    each of the <acronym>URI</acronym> parts is optional.  The following
+    examples illustrate valid <acronym>URI</acronym> syntax uses:
+<synopsis>
+postgresql://
+postgresql://localhost
+postgresql://localhost:5433
+postgresql://localhost/mydb
+postgresql://user@localhost
+postgresql://user:secret@localhost
+postgresql://other@localhost/otherdb
+</synopsis>
+   </para>
+
+   <para>
+    Percent-encoding may be used to include a symbol with special meaning in
+    any of the <acronym>URI</acronym> parts.
+   </para>
+
+   <para>
+    Additional connection parameters may optionally follow the base <acronym>URI</acronym>.
+    Any connection parameters not corresponding to key words listed
+    in <xref linkend="libpq-paramkeywords"> are ignored and a warning message
+    about them is sent to <filename>stderr</filename>.
+   </para>
+
+   <para>
+    For improved compatibility with JDBC connection <acronym>URI</acronym>
+    syntax, instances of parameter <literal>ssl=true</literal> are translated
+    into <literal>sslmode=require</literal> (see above.)
+   </para>
+
+   <para>
+    The host part may be either hostname or an IP address.  To specify an
+    IPv6 host address, enclose it in square brackets:
+<synopsis>
+postgresql://[2001:db8::1234]/database
+</synopsis>
+    As a special case, a host part which starts with <symbol>/</symbol> is
+    treated as a local Unix socket directory to look for the connection
+    socket special file:
+<synopsis>
+postgresql:///path/to/pgsql/socket/dir
+</synopsis>
+    The whole connection string up to the extra parameters designator
+    (<symbol>?</symbol>) or the port designator (<symbol>:</symbol>) is treated
+    as the absolute path to the socket directory
+    (<literal>/path/to/pgsql/socket/dir</literal> in this example.)  To specify
+    a non-default database name in this case you can use either of the following
+    syntaxes:
+<synopsis>
+postgresql:///path/to/pgsql/socket/dir?dbname=otherdb
+postgresql:///path/to/pgsql/socket/dir:5432/otherdb
+</synopsis>
+   </para>
+  </sect2>
+
  </sect1>
 
  <sect1 id="libpq-status">
diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index b8491015f4e..bdcadf36928 100644
--- a/doc/src/sgml/ref/psql-ref.sgml
+++ b/doc/src/sgml/ref/psql-ref.sgml
@@ -115,7 +115,10 @@ PostgreSQL documentation
        argument on the command line.
       </para>
       <para>
-       If this parameter contains an <symbol>=</symbol> sign, it is treated as a
+       If this parameter contains an <symbol>=</symbol> sign or starts
+       with a valid <acronym>URI</acronym> prefix
+       (<literal>postgresql://</literal>
+       or <literal>postgres://</literal>), it is treated as a
        <parameter>conninfo</parameter> string. See <xref linkend="libpq-connect"> for more information.
       </para>
       </listitem>
@@ -596,11 +599,13 @@ PostgreSQL documentation
 
     <para>
      An alternative way to specify connection parameters is in a
-     <parameter>conninfo</parameter> string, which is used instead of a
-     database name. This mechanism give you very wide control over the
+     <parameter>conninfo</parameter> string or
+     a <acronym>URI</acronym>, which is used instead of a database
+     name. This mechanism give you very wide control over the
      connection. For example:
 <programlisting>
 $ <userinput>psql "service=myservice sslmode=require"</userinput>
+$ <userinput>psql postgresql://dbmaster:5433/mydb?sslmode=require</userinput>
 </programlisting>
      This way you can also use LDAP for connection parameter lookup as
      described in <xref linkend="libpq-ldap">.