5 files changed, 68 insertions, 23 deletions
diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index fdb2404f5ed..2483dbbad47 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -1467,9 +1467,10 @@ do_connect(char *dbname, char *user, char *host, char *port)
 	PGconn	   *o_conn = pset.db,
 			   *n_conn;
 	char	   *password = NULL;
+	bool		keep_password;
+	bool		has_connection_string;
 
-	if (!dbname)
-		dbname = PQdb(o_conn);
+	/* grab values from the old connection, unless supplied by caller */
 	if (!user)
 		user = PQuser(o_conn);
 	if (!host)
@@ -1477,6 +1478,27 @@ do_connect(char *dbname, char *user, char *host, char *port)
 	if (!port)
 		port = PQport(o_conn);
 
+	has_connection_string =
+		dbname ? recognized_connection_string(dbname) : false;
+
+	/*
+	 * Any change in the parameters read above makes us discard the password.
+	 * We also discard it if we're to use a conninfo rather than the positional
+	 * syntax.
+	 */
+	keep_password =
+		((strcmp(user, PQuser(o_conn)) == 0) &&
+		 (!host || strcmp(host, PQhost(o_conn)) == 0) &&
+		 (strcmp(port, PQport(o_conn)) == 0) &&
+		 !has_connection_string);
+
+	/*
+	 * Grab dbname from old connection unless supplied by caller.  No password
+	 * discard if this changes: passwords aren't (usually) database-specific.
+	 */
+	if (!dbname)
+		dbname = PQdb(o_conn);
+
 	/*
 	 * If the user asked to be prompted for a password, ask for one now. If
 	 * not, use the password from the old connection, provided the username
@@ -1491,7 +1513,7 @@ do_connect(char *dbname, char *user, char *host, char *port)
 	{
 		password = prompt_for_password(user);
 	}
-	else if (o_conn && user && strcmp(PQuser(o_conn), user) == 0)
+	else if (o_conn && keep_password)
 	{
 		password = strdup(PQpass(o_conn));
 	}
@@ -1501,23 +1523,30 @@ do_connect(char *dbname, char *user, char *host, char *port)
 #define PARAMS_ARRAY_SIZE	8
 		const char **keywords = pg_malloc(PARAMS_ARRAY_SIZE * sizeof(*keywords));
 		const char **values = pg_malloc(PARAMS_ARRAY_SIZE * sizeof(*values));
-
-		keywords[0] = "host";
-		values[0] = host;
-		keywords[1] = "port";
-		values[1] = port;
-		keywords[2] = "user";
-		values[2] = user;
-		keywords[3] = "password";
-		values[3] = password;
-		keywords[4] = "dbname";
-		values[4] = dbname;
-		keywords[5] = "fallback_application_name";
-		values[5] = pset.progname;
-		keywords[6] = "client_encoding";
-		values[6] = (pset.notty || getenv("PGCLIENTENCODING")) ? NULL : "auto";
-		keywords[7] = NULL;
-		values[7] = NULL;
+		int			paramnum = 0;
+
+		keywords[0] = "dbname";
+		values[0] = dbname;
+
+		if (!has_connection_string)
+		{
+			keywords[++paramnum] = "host";
+			values[paramnum] = host;
+			keywords[++paramnum] = "port";
+			values[paramnum] = port;
+			keywords[++paramnum] = "user";
+			values[paramnum] = user;
+		}
+		keywords[++paramnum] = "password";
+		values[paramnum] = password;
+		keywords[++paramnum] = "fallback_application_name";
+		values[paramnum] = pset.progname;
+		keywords[++paramnum] = "client_encoding";
+		values[paramnum] = (pset.notty || getenv("PGCLIENTENCODING")) ? NULL : "auto";
+
+		/* add array terminator */
+		keywords[++paramnum] = NULL;
+		values[paramnum] = NULL;
 
 		n_conn = PQconnectdbParams(keywords, values, true);
 
diff --git a/src/bin/psql/common.c b/src/bin/psql/common.c
index abb108265dd..5ab2c230363 100644
--- a/src/bin/psql/common.c
+++ b/src/bin/psql/common.c
@@ -1574,3 +1574,15 @@ expand_tilde(char **filename)
 
 	return *filename;
 }
+
+/*
+ * Recognized connection string contains a "=" in it.
+ *
+ * Must be consistent with conninfo_parse: anything for which this
+ * returns true should at least look like it's parseable by that routine.
+ */
+bool
+recognized_connection_string(const char *connstr)
+{
+	return strchr(connstr, '=') != NULL;
+}
diff --git a/src/bin/psql/common.h b/src/bin/psql/common.h
index a26b8682be6..20951d7ef4e 100644
--- a/src/bin/psql/common.h
+++ b/src/bin/psql/common.h
@@ -63,4 +63,6 @@ extern const char *session_username(void);
 
 extern char *expand_tilde(char **filename);
 
+extern bool recognized_connection_string(const char *connstr);
+
 #endif   /* COMMON_H */
diff --git a/src/bin/psql/help.c b/src/bin/psql/help.c
index 64bf407374f..574f52ec0af 100644
--- a/src/bin/psql/help.c
+++ b/src/bin/psql/help.c
@@ -251,7 +251,7 @@ slashUsage(unsigned short int pager)
 	fprintf(output, "\n");
 
 	fprintf(output, _("Connection\n"));
-	fprintf(output, _("  \\c[onnect] [DBNAME|- USER|- HOST|- PORT|-]\n"
+	fprintf(output, _("  \\c[onnect] {[DBNAME|- USER|- HOST|- PORT|-] | conninfo}\n"
 	"                         connect to new database (currently \"%s\")\n"),
 			currdb);
 	fprintf(output, _("  \\encoding [ENCODING]   show or set client encoding\n"));
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index d90d2814c5f..8f9ab696106 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -2776,8 +2776,10 @@ psql_completion(char *text, int start, int end)
 /* Backslash commands */
 /* TODO:  \dc \dd \dl */
 	else if (strcmp(prev_wd, "\\connect") == 0 || strcmp(prev_wd, "\\c") == 0)
-		COMPLETE_WITH_QUERY(Query_for_list_of_databases);
-
+	{
+		if (!recognized_connection_string(text))
+			COMPLETE_WITH_QUERY(Query_for_list_of_databases);
+	}
 	else if (strncmp(prev_wd, "\\da", strlen("\\da")) == 0)
 		COMPLETE_WITH_SCHEMA_QUERY(Query_for_list_of_aggregates, NULL);
 	else if (strncmp(prev_wd, "\\db", strlen("\\db")) == 0)