Use "replication" as the database name when constructing a connection

string for a streaming replication connection. It's ignored by the
server, but allows libpq to pick up the password from .pgpass where
"replication" is specified as the database name.

Patch by Fujii Masao per Tom's suggestion, with some wording changes by me.

doc/src/sgml/high-availability.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/high-availability.sgml,v 1.72 2010/06/10 08:13:49 itagaki Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/high-availability.sgml,v 1.73 2010/06/11 10:13:08 heikki Exp $ -->
 
 <chapter id="high-availability">
  <title>High Availability, Load Balancing, and Replication</title>
@@ -818,8 +818,10 @@ host    replication     foo             192.168.1.100/32        md5
     </para>
     <para>
      The host name and port number of the primary, connection user name,
-     and password are specified in the <filename>recovery.conf</> file or
-     the corresponding environment variable on the standby.
+     and password are specified in the <filename>recovery.conf</> file.
+     The password can also be set in the <filename>~/.pgpass</> file on the
+     standby (specify <literal>replication</> in the <replaceable>database</>
+     field).
      For example, if the primary is running on host IP <literal>192.168.1.50</>,
      port <literal>5432</literal>, the superuser's name for replication is
      <literal>foo</>, and the password is <literal>foopass</>, the administrator

doc/src/sgml/libpq.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.306 2010/05/26 23:49:18 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/libpq.sgml,v 1.307 2010/06/11 10:13:08 heikki Exp $ -->
 
 <chapter id="libpq">
  <title><application>libpq</application> - C Library</title>
@@ -6233,7 +6233,8 @@ myEventProc(PGEventId evtId, void *evtInfo, void *passThrough)
    A host name of <literal>localhost</> matches both TCP (host name
    <literal>localhost</>) and Unix domain socket (<literal>pghost</> empty
    or the default socket directory) connections coming from the local
-   machine.
+   machine. In a standby server, a database name of <literal>replication</>
+   matches streaming replication connections made to the master server.
   </para>
 
   <para>

doc/src/sgml/recovery-config.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/recovery-config.sgml,v 2.7 2010/06/10 08:13:49 itagaki Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/recovery-config.sgml,v 2.8 2010/06/11 10:13:09 heikki Exp $ -->
 
 <chapter Id="recovery-config">
   <title>Recovery Configuration</title>
@@ -268,9 +268,10 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"'  # Windows
           primary (see
           <xref linkend="streaming-replication-authentication">).
           A password needs to be provided too, if the primary demands password
-          authentication.  (The password can be provided either in
-          the <varname>primary_conninfo</varname> string or in a separate
-          <filename>~/.pgpass</> file on the standby server.)
+          authentication.  It can be provided in the
+          <varname>primary_conninfo</varname> string, or in a separate
+          <filename>~/.pgpass</> file on the standby server (use
+          <literal>replication</> as the database name).
           Do not specify a database name in the
           <varname>primary_conninfo</varname> string.
          </para>

src/backend/replication/libpqwalreceiver/libpqwalreceiver.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c,v 1.10 2010/04/21 03:32:53 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c,v 1.11 2010/06/11 10:13:09 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -77,7 +77,7 @@ _PG_init(void)
 static bool
 libpqrcv_connect(char *conninfo, XLogRecPtr startpoint)
 {
-	char		conninfo_repl[MAXCONNINFO + 18];
+	char		conninfo_repl[MAXCONNINFO + 37];
 	char	   *primary_sysid;
 	char		standby_sysid[32];
 	TimeLineID	primary_tli;
@@ -85,8 +85,14 @@ libpqrcv_connect(char *conninfo, XLogRecPtr startpoint)
 	PGresult   *res;
 	char		cmd[64];
 
-	/* Connect using deliberately undocumented parameter: replication */
-	snprintf(conninfo_repl, sizeof(conninfo_repl), "%s replication=true", conninfo);
+	/*
+	 * Connect using deliberately undocumented parameter: replication.
+	 * The database name is ignored by the server in replication mode, but
+	 * specify "replication" for .pgpass lookup.
+	 */
+	snprintf(conninfo_repl, sizeof(conninfo_repl),
+			 "%s dbname=replication replication=true",
+			 conninfo);
 
 	streamConn = PQconnectdb(conninfo_repl);
 	if (PQstatus(streamConn) != CONNECTION_OK)