Support load balancing in libpq

From e4a9c66fb34270bff62eaded37042bc5521c905c Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 22 Jun 2022 09:39:13 +0200
Subject: [PATCH] Support load balancing in libpq

Load balancing connections across multiple read replicas is a pretty
common way of scaling out read queries. There are two main ways of doing
so, both with their own advantages and disadvantages:
1. Load balancing at the client level
2. Load balancing by connecting to an intermediary load balancer

Option 1 has been supported by JDBC (Java) for 8 years and Npgsql (C#)
merged support about a year ago. This patch adds the same functionality
to libpq. The way it's implemented is the same as the implementation of
JDBC, and contains two levels of load balancing:
1. The given hosts are randomly shuffled, before resolving them
    one-by-one.
2. Once a host its addresses get resolved, those addresses are shuffled,
    before trying to connect to them one-by-one.
---
 doc/src/sgml/libpq.sgml           |  17 +++
 src/include/libpq/pqcomm.h        |   6 +
 src/interfaces/libpq/fe-connect.c | 204 +++++++++++++++++++++++++-----
 src/interfaces/libpq/libpq-int.h  |   7 +-
 4 files changed, 202 insertions(+), 32 deletions(-)

diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 37ec3cb4e5..149cf25854 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1317,6 +1317,23 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
       </listitem>
      </varlistentry>
 
+     <varlistentry id="libpq-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls whether the client load balances connections across hosts and
+        adresses. The default value is 0, meaning off, this means that hosts are
+        tried in order they are provided and addresses are tried in the order
+        they are received from DNS or a hosts file. If this value is set to 1,
+        meaning on, the hosts and address that are tried in random order.
+        Subsequent queries once connected will still be sent to the same server.
+        Setting this to 1, is mostly useful when opening multiple connections at
+        the same time, possibly from different machines. This way connections
+        can be load balanced across multiple Postgres servers.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="libpq-keepalives" xreflabel="keepalives">
       <term><literal>keepalives</literal></term>
       <listitem>
diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index b418283d5f..f67b334887 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -65,6 +65,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+}			AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 6e936bbff3..6dcbbecc39 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -23,6 +23,7 @@
 
 #include "common/ip.h"
 #include "common/link-canary.h"
+#include "common/pg_prng.h"
 #include "common/scram-common.h"
 #include "common/string.h"
 #include "fe-auth.h"
@@ -244,6 +245,10 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Fallback-Application-Name", "", 64,
 	offsetof(struct pg_conn, fbappname)},
 
+	{"load_balance_hosts", NULL, NULL, NULL,
+		"Load-Balance", "", 0,	/* should be just '0' or '1' */
+	offsetof(struct pg_conn, loadbalance)},
+
 	{"keepalives", NULL, NULL, NULL,
 		"TCP-Keepalives", "", 1,	/* should be just '0' or '1' */
 	offsetof(struct pg_conn, keepalives)},
@@ -367,6 +372,9 @@ static const PQEnvironmentOption EnvironmentOptions[] =
 	}
 };
 
+static bool libpq_prng_initialized = false;
+static pg_prng_state libpq_prng_state;
+
 /* The connection URI must start with either of the following designators: */
 static const char uri_designator[] = "postgresql://";
 static const char short_uri_designator[] = "postgres://";
@@ -382,6 +390,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *conninfo,
@@ -427,6 +436,7 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static int	loadBalance(PGconn *conn);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1015,6 +1025,41 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+static void
+libpq_prng_init()
+{
+	if (libpq_prng_initialized)
+	{
+		return;
+	}
+
+	/*
+	 * Set a different global seed in every process.  We want something
+	 * unpredictable, so if possible, use high-quality random bits for the
+	 * seed.  Otherwise, fall back to a seed based on timestamp and PID.
+	 */
+	if (unlikely(!pg_prng_strong_seed(&libpq_prng_state)))
+	{
+		uint64		rseed;
+		time_t		now = time(NULL);
+
+		/*
+		 * Since PIDs and timestamps tend to change more frequently in their
+		 * least significant bits, shift the timestamp left to allow a larger
+		 * total number of seeds in a given time period.  Since that would
+		 * leave only 20 bits of the timestamp that cycle every ~1 second,
+		 * also mix in some higher bits.
+		 */
+		rseed = ((uint64) getpid()) ^
+			((uint64) now << 12) ^
+			((uint64) now >> 20);
+
+		pg_prng_seed(&libpq_prng_state, rseed);
+	}
+	libpq_prng_initialized = true;
+}
+
+
 /*
  *		connectOptions2
  *
@@ -1027,6 +1072,7 @@ static bool
 connectOptions2(PGconn *conn)
 {
 	int			i;
+	int			loadbalancehosts = loadBalance(conn);
 
 	/*
 	 * Allocate memory for details about each host to which we might possibly
@@ -1178,6 +1224,31 @@ connectOptions2(PGconn *conn)
 			return false;
 		}
 	}
+	if (loadbalancehosts < 0)
+	{
+		appendPQExpBufferStr(&conn->errorMessage,
+							 libpq_gettext("loadbalance parameter must be an integer\n"));
+		return false;
+	}
+
+	if (loadbalancehosts)
+	{
+		/*
+		 * Shuffle connhost with a Durstenfeld/Knuth version of the
+		 * Fisher-Yates shuffle. Source:
+		 * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
+		 */
+		libpq_prng_init();
+		for (i = conn->nconnhost - 1; i > 0; i--)
+		{
+			int			j = pg_prng_double(&libpq_prng_state) * (i + 1);
+			pg_conn_host temp = conn->connhost[j];
+
+			conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
 
 	/*
 	 * If user name was not given, fetch it.  (Most likely, the fetch will
@@ -1772,6 +1843,27 @@ connectFailureMessage(PGconn *conn, int errorno)
 							 libpq_gettext("\tIs the server running on that host and accepting TCP/IP connections?\n"));
 }
 
+/*
+ * Should we load balance across hosts? Returns 1 if yes, 0 if no, and -1 if
+ * conn->loadbalance is set to a value which is not parseable as an integer.
+ */
+static int
+loadBalance(PGconn *conn)
+{
+	char	   *ep;
+	int			val;
+
+	if (conn->loadbalance == NULL)
+	{
+		return 0;
+	}
+	val = strtol(conn->loadbalance, &ep, 10);
+	if (*ep)
+		return -1;
+	return val != 0 ? 1 : 0;
+}
+
+
 /*
  * Should we use keepalives?  Returns 1 if yes, 0 if no, and -1 if
  * conn->keepalives is set to a value which is not parseable as an
@@ -2129,7 +2221,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2173,11 +2265,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2325,9 +2417,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2340,6 +2432,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2380,7 +2473,6 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2405,8 +2497,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					appendPQExpBuffer(&conn->errorMessage,
 									  libpq_gettext("could not translate host name \"%s\" to address: %s\n"),
@@ -2418,8 +2510,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					appendPQExpBuffer(&conn->errorMessage,
 									  libpq_gettext("could not parse network address \"%s\": %s\n"),
@@ -2430,7 +2522,6 @@ keep_going:						/* We will come back to here until there is
 
 			case CHT_UNIX_SOCKET:
 #ifdef HAVE_UNIX_SOCKETS
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2446,8 +2537,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					appendPQExpBuffer(&conn->errorMessage,
 									  libpq_gettext("could not translate Unix-domain socket path \"%s\" to address: %s\n"),
@@ -2460,8 +2551,15 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
+		if (!store_conn_addrinfo(conn, addrlist))
+		{
+			appendPQExpBufferStr(&conn->errorMessage,
+								 libpq_gettext("out of memory\n"));
+			goto error_return;
+		}
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2518,30 +2616,29 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2557,7 +2654,7 @@ keep_going:						/* We will come back to here until there is
 						conn->connip = strdup(host_addr);
 
 					/* Try to create the socket */
-					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
+					conn->sock = socket(addr_cur->family, SOCK_STREAM, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2568,7 +2665,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2595,7 +2692,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2624,7 +2721,7 @@ keep_going:						/* We will come back to here until there is
 					}
 #endif							/* F_SETFD */
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2718,8 +2815,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4172,6 +4269,54 @@ freePGconn(PGconn *conn)
 	free(conn);
 }
 
+
+static bool
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+	{
+		return false;
+	}
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+	if (loadBalance(conn))
+	{
+		/*
+		 * Shuffle addr with a Durstenfeld/Knuth version of the Fisher-Yates
+		 * shuffle. Source:
+		 * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
+		 */
+		libpq_prng_init();
+		for (int i = conn->naddr - 1; i > 0; i--)
+		{
+			int			j = pg_prng_double(&libpq_prng_state) * (i + 1);
+			AddrInfo	temp = conn->addr[j];
+
+			conn->addr[j] = conn->addr[i];
+			conn->addr[i] = temp;
+		}
+	}
+	return true;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4179,11 +4324,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 3db6a17db4..3f60bfa2a0 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -370,6 +370,7 @@ struct pg_conn
 	char	   *pgpassfile;		/* path to a file containing password(s) */
 	char	   *channel_binding;	/* channel binding mode
 									 * (require,prefer,disable) */
+	char	   *loadbalance;	/* load balance over hosts */
 	char	   *keepalives;		/* use TCP keepalives? */
 	char	   *keepalives_idle;	/* time between TCP keepalives */
 	char	   *keepalives_interval;	/* time between TCP keepalive
@@ -458,8 +459,10 @@ struct pg_conn
 	PGTargetServerType target_server_type;	/* desired session properties */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
+	int			naddr;			/* # of addrs returned by getaddrinfo */
+	int			whichaddr;		/* the addr currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	int			addrlist_family;	/* needed to know how to free addrlist */
 	bool		send_appname;	/* okay to send application_name? */
 
-- 
2.17.1

From db8ee43abd7463858422af17e0fad2ca6939387d Mon Sep 17 00:00:00 2001
From: Jelte Fennema <github-tech@jeltef.nl>
Date: Mon, 12 Sep 2022 09:44:06 +0200
Subject: [PATCH] Support load balancing in libpq

Load balancing connections across multiple read replicas is a pretty
common way of scaling out read queries. There are two main ways of doing
so, both with their own advantages and disadvantages:
1. Load balancing at the client level
2. Load balancing by connecting to an intermediary load balancer

Both JBDC (Java) and Npgsql (C#) already support client level load
balancing (option #1). This patch implements client level load balancing
for libpq as well. To stay consistent with the JDBC and Npgsql part of
the  ecosystem, a similar implementation and name for the option are
used. It contains two levels of load balancing:
1. The given hosts are randomly shuffled, before resolving them
    one-by-one.
2. Once a host its addresses get resolved, those addresses are shuffled,
    before trying to connect to them one-by-one.
---
 .../postgres_fdw/expected/postgres_fdw.out    |   2 +-
 doc/src/sgml/libpq.sgml                       |  17 ++
 src/include/libpq/pqcomm.h                    |   6 +
 src/interfaces/libpq/fe-connect.c             | 208 +++++++++++++++---
 src/interfaces/libpq/libpq-int.h              |  11 +-
 5 files changed, 210 insertions(+), 34 deletions(-)

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 7bf35602b0..00cc94d08e 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -9627,7 +9627,7 @@ DO $d$
     END;
 $d$;
 ERROR:  invalid option "password"
-HINT:  Valid options in this context are: service, passfile, channel_binding, connect_timeout, dbname, host, hostaddr, port, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, tcp_user_timeout, sslmode, sslcompression, sslcert, sslkey, sslrootcert, sslcrl, sslcrldir, sslsni, requirepeer, ssl_min_protocol_version, ssl_max_protocol_version, gssencmode, krbsrvname, gsslib, target_session_attrs, use_remote_estimate, fdw_startup_cost, fdw_tuple_cost, extensions, updatable, truncatable, fetch_size, batch_size, async_capable, parallel_commit, keep_connections
+HINT:  Valid options in this context are: service, passfile, channel_binding, connect_timeout, dbname, host, hostaddr, port, options, application_name, load_balance_hosts, keepalives, keepalives_idle, keepalives_interval, keepalives_count, tcp_user_timeout, sslmode, sslcompression, sslcert, sslkey, sslrootcert, sslcrl, sslcrldir, sslsni, requirepeer, ssl_min_protocol_version, ssl_max_protocol_version, gssencmode, krbsrvname, gsslib, target_session_attrs, use_remote_estimate, fdw_startup_cost, fdw_tuple_cost, extensions, updatable, truncatable, fetch_size, batch_size, async_capable, parallel_commit, keep_connections
 CONTEXT:  SQL statement "ALTER SERVER loopback_nopw OPTIONS (ADD password 'dummypw')"
 PL/pgSQL function inline_code_block line 3 at EXECUTE
 -- If we add a password for our user mapping instead, we should get a different
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 8a1a9e9932..26b3f0c36f 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1316,6 +1316,23 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
       </listitem>
      </varlistentry>
 
+     <varlistentry id="libpq-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls whether the client load balances connections across hosts and
+        adresses. The default value is 0, meaning off, this means that hosts are
+        tried in order they are provided and addresses are tried in the order
+        they are received from DNS or a hosts file. If this value is set to 1,
+        meaning on, the hosts and address that are tried in random order.
+        Subsequent queries once connected will still be sent to the same server.
+        Setting this to 1, is mostly useful when opening multiple connections at
+        the same time, possibly from different machines. This way connections
+        can be load balanced across multiple Postgres servers.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="libpq-keepalives" xreflabel="keepalives">
       <term><literal>keepalives</literal></term>
       <listitem>
diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index fcf68df39b..39e93b1392 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+}			AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 917b19e0e9..d4f9d6180c 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -241,6 +241,10 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Fallback-Application-Name", "", 64,
 	offsetof(struct pg_conn, fbappname)},
 
+	{"load_balance_hosts", NULL, NULL, NULL,
+		"Load-Balance", "", 0,	/* should be just '0' or '1' */
+	offsetof(struct pg_conn, loadbalance)},
+
 	{"keepalives", NULL, NULL, NULL,
 		"TCP-Keepalives", "", 1,	/* should be just '0' or '1' */
 	offsetof(struct pg_conn, keepalives)},
@@ -379,6 +383,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *conninfo,
@@ -424,6 +429,7 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static int	loadBalance(PGconn *conn);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1008,6 +1014,35 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on timestamp and PID.
+ */
+static void
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		time_t		now = time(NULL);
+
+		/*
+		 * Since PIDs and timestamps tend to change more frequently in their
+		 * least significant bits, shift the timestamp left to allow a larger
+		 * total number of seeds in a given time period.  Since that would
+		 * leave only 20 bits of the timestamp that cycle every ~1 second,
+		 * also mix in some higher bits.
+		 */
+		rseed = ((uint64) getpid()) ^
+			((uint64) now << 12) ^
+			((uint64) now >> 20);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+}
+
+
 /*
  *		connectOptions2
  *
@@ -1020,6 +1055,7 @@ static bool
 connectOptions2(PGconn *conn)
 {
 	int			i;
+	int			loadbalancehosts = loadBalance(conn);
 
 	/*
 	 * Allocate memory for details about each host to which we might possibly
@@ -1167,6 +1203,32 @@ connectOptions2(PGconn *conn)
 		}
 	}
 
+	if (loadbalancehosts < 0)
+	{
+		appendPQExpBufferStr(&conn->errorMessage,
+							 libpq_gettext("loadbalance parameter must be an integer\n"));
+		return false;
+	}
+
+	if (loadbalancehosts)
+	{
+		/*
+		 * Shuffle connhost with a Durstenfeld/Knuth version of the
+		 * Fisher-Yates shuffle. Source:
+		 * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
+		 */
+		libpq_prng_init(conn);
+		for (i = conn->nconnhost - 1; i > 0; i--)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
+
 	/*
 	 * If user name was not given, fetch it.  (Most likely, the fetch will
 	 * fail, since the only way we get here is if pg_fe_getauthname() failed
@@ -1745,6 +1807,27 @@ connectFailureMessage(PGconn *conn, int errorno)
 							 libpq_gettext("\tIs the server running on that host and accepting TCP/IP connections?\n"));
 }
 
+/*
+ * Should we load balance across hosts? Returns 1 if yes, 0 if no, and -1 if
+ * conn->loadbalance is set to a value which is not parseable as an integer.
+ */
+static int
+loadBalance(PGconn *conn)
+{
+	char	   *ep;
+	int			val;
+
+	if (conn->loadbalance == NULL)
+	{
+		return 0;
+	}
+	val = strtol(conn->loadbalance, &ep, 10);
+	if (*ep)
+		return -1;
+	return val != 0 ? 1 : 0;
+}
+
+
 /*
  * Should we use keepalives?  Returns 1 if yes, 0 if no, and -1 if
  * conn->keepalives is set to a value which is not parseable as an
@@ -2102,7 +2185,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2146,11 +2229,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2298,9 +2381,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2313,6 +2396,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2353,7 +2437,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2378,8 +2462,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					appendPQExpBuffer(&conn->errorMessage,
 									  libpq_gettext("could not translate host name \"%s\" to address: %s\n"),
@@ -2391,8 +2475,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					appendPQExpBuffer(&conn->errorMessage,
 									  libpq_gettext("could not parse network address \"%s\": %s\n"),
@@ -2402,7 +2486,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2418,8 +2502,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					appendPQExpBuffer(&conn->errorMessage,
 									  libpq_gettext("could not translate Unix-domain socket path \"%s\" to address: %s\n"),
@@ -2429,8 +2513,15 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		if (!store_conn_addrinfo(conn, addrlist))
+		{
+			pg_freeaddrinfo_all(hint.ai_family, addrlist);
+			appendPQExpBufferStr(&conn->errorMessage,
+								 libpq_gettext("out of memory\n"));
+			goto error_return;
+		}
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2487,30 +2578,29 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2526,7 +2616,7 @@ keep_going:						/* We will come back to here until there is
 						conn->connip = strdup(host_addr);
 
 					/* Try to create the socket */
-					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
+					conn->sock = socket(addr_cur->family, SOCK_STREAM, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2537,7 +2627,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2564,7 +2654,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2593,7 +2683,7 @@ keep_going:						/* We will come back to here until there is
 					}
 #endif							/* F_SETFD */
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2687,8 +2777,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4092,6 +4182,63 @@ freePGconn(PGconn *conn)
 	free(conn);
 }
 
+
+/*
+ * Copies over the AddrInfos from addrlist to the PGconn.
+ */
+static bool
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+	{
+		return false;
+	}
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	if (loadBalance(conn))
+	{
+		/*
+		 * Shuffle addr with a Durstenfeld/Knuth version of the Fisher-Yates
+		 * shuffle. Source:
+		 * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
+		 *
+		 * We don't need to initialize conn->prng_state here, because that
+		 * already happened in connectOptions2.
+		 */
+		for (int i = conn->naddr - 1; i > 0; i--)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			AddrInfo	temp = conn->addr[j];
+
+			conn->addr[j] = conn->addr[i];
+			conn->addr[i] = temp;
+		}
+	}
+	return true;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4099,11 +4246,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index c75ed63a2c..1403b32667 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -82,6 +82,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -373,6 +375,7 @@ struct pg_conn
 	char	   *pgpassfile;		/* path to a file containing password(s) */
 	char	   *channel_binding;	/* channel binding mode
 									 * (require,prefer,disable) */
+	char	   *loadbalance;	/* load balance over hosts */
 	char	   *keepalives;		/* use TCP keepalives? */
 	char	   *keepalives_idle;	/* time between TCP keepalives */
 	char	   *keepalives_interval;	/* time between TCP keepalive
@@ -461,8 +464,10 @@ struct pg_conn
 	PGTargetServerType target_server_type;	/* desired session properties */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
+	int			naddr;			/* number of addrs returned by getaddrinfo */
+	int			whichaddr;		/* the addr currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	int			addrlist_family;	/* needed to know how to free addrlist */
 	bool		send_appname;	/* okay to send application_name? */
 
@@ -477,6 +482,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
-- 
2.34.1

From 062f8fa147e642d5ffb3e54cbf4d94e15350b216 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <github-tech@jeltef.nl>
Date: Mon, 12 Sep 2022 09:44:06 +0200
Subject: [PATCH] Support load balancing in libpq

Load balancing connections across multiple read replicas is a pretty
common way of scaling out read queries. There are two main ways of doing
so, both with their own advantages and disadvantages:
1. Load balancing at the client level
2. Load balancing by connecting to an intermediary load balancer

Both JBDC (Java) and Npgsql (C#) already support client level load
balancing (option #1). This patch implements client level load balancing
for libpq as well. To stay consistent with the JDBC and Npgsql part of
the  ecosystem, a similar implementation and name for the option are
used. It contains two levels of load balancing:
1. The given hosts are randomly shuffled, before resolving them
    one-by-one.
2. Once a host its addresses get resolved, those addresses are shuffled,
    before trying to connect to them one-by-one.
---
 .cirrus.yml                               |  14 ++
 doc/src/sgml/libpq.sgml                   |  48 +++++
 src/include/libpq/pqcomm.h                |   6 +
 src/interfaces/libpq/fe-connect.c         | 231 +++++++++++++++++++---
 src/interfaces/libpq/libpq-int.h          |  12 +-
 src/interfaces/libpq/meson.build          |   1 +
 src/interfaces/libpq/t/003_loadbalance.pl | 134 +++++++++++++
 7 files changed, 413 insertions(+), 33 deletions(-)
 create mode 100644 src/interfaces/libpq/t/003_loadbalance.pl

diff --git a/.cirrus.yml b/.cirrus.yml
index 531cfe96f6..8615c9f74d 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -199,6 +199,14 @@ task:
     mkdir -m 770 /tmp/cores
     chown root:postgres /tmp/cores
     sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core'
+
+  setup_hosts_file_script: |
+    cat >> /etc/hosts <<-EOF
+      127.0.0.1 pg-loadbalancetest
+      127.0.0.2 pg-loadbalancetest
+      127.0.0.3 pg-loadbalancetest
+    EOF
+
   setup_additional_packages_script: |
     #apt-get update
     #DEBIAN_FRONTEND=noninteractive apt-get -y install ...
@@ -444,6 +452,12 @@ task:
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
+  setup_hosts_file_script: |
+    echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    type c:\Windows\System32\Drivers\etc\hosts
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 3c9bd3d673..1d578b8a45 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1316,6 +1316,54 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
       </listitem>
      </varlistentry>
 
+     <varlistentry id="libpq-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls whether the client load balances connections across hosts and
+        adresses. The default value is 0, meaning off, this means that hosts are
+        tried in order they are provided and addresses are tried in the order
+        they are received from DNS or a hosts file. If this value is set to 1,
+        meaning on, the hosts and addresses that they resolve to are tried in
+        random order. Subsequent queries once connected will still be sent to
+        the same server. Setting this to 1, is mostly useful when opening
+        multiple connections at the same time, possibly from different machines.
+        This way connections can be load balanced across multiple Postgres
+        servers.
+       </para>
+       <para>
+        When providing multiple hosts, these hosts are resolved in random order.
+        Then if that host resolves to multiple addresses, these addresses are
+        connected to in random order. Only once all addresses for a single host
+        have been tried, the addresses for the next random host will be
+        resolved. This behaviour can lead to non-uniform address selection in
+        certain cases. Such as when not all hosts resolve to the same number of
+        addresses, or when multiple hosts resolve to the same address. So if you
+        want uniform load balancing, this is something to keep in mind. However,
+        non-uniform load balancing also has usecases, e.g. providing the
+        hostname of a larger server multiple times in the host string so it gets
+        more requests.
+       </para>
+       <para>
+        When using this setting it's recommended to also configure a reasonable
+        value for <xref linkend="libpq-connect-connect-timeout"/>. Because then,
+        if one of the nodes that are used for load balancing is not responding,
+        a new node will be tried.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-random-seed" xreflabel="random_seed">
+      <term><literal>random_seed</literal></term>
+      <listitem>
+       <para>
+        Sets the random seed that is used by <xref linkend="libpq-load-balance-hosts"/>
+        to randomize the host order. This option is mostly useful when running
+        tests that require a stable random order.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="libpq-keepalives" xreflabel="keepalives">
       <term><literal>keepalives</literal></term>
       <listitem>
diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index fcf68df39b..39e93b1392 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+}			AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 746e9b4f1e..164d4ae073 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -241,6 +241,14 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Fallback-Application-Name", "", 64,
 	offsetof(struct pg_conn, fbappname)},
 
+	{"load_balance_hosts", NULL, NULL, NULL,
+		"Load-Balance", "", 1,	/* should be just '0' or '1' */
+	offsetof(struct pg_conn, loadbalance)},
+
+	{"random_seed", NULL, NULL, NULL,
+		"Random-Seed", "", 10,	/* strlen(INT32_MAX) == 10 */
+	offsetof(struct pg_conn, randomseed)},
+
 	{"keepalives", NULL, NULL, NULL,
 		"TCP-Keepalives", "", 1,	/* should be just '0' or '1' */
 	offsetof(struct pg_conn, keepalives)},
@@ -379,6 +387,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *connstr,
@@ -424,6 +433,9 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static int	loadBalance(PGconn *conn);
+static bool parse_int_param(const char *value, int *result, PGconn *conn,
+							const char *context);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1008,6 +1020,46 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on timestamp and PID.
+ */
+static bool
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(conn->randomseed))
+	{
+		int			rseed;
+
+		if (!parse_int_param(conn->randomseed, &rseed, conn, "random_seed"))
+		{
+			return false;
+		};
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	else if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		time_t		now = time(NULL);
+
+		/*
+		 * Since PIDs and timestamps tend to change more frequently in their
+		 * least significant bits, shift the timestamp left to allow a larger
+		 * total number of seeds in a given time period.  Since that would
+		 * leave only 20 bits of the timestamp that cycle every ~1 second,
+		 * also mix in some higher bits.
+		 */
+		rseed = ((uint64) getpid()) ^
+			((uint64) now << 12) ^
+			((uint64) now >> 20);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	return true;
+}
+
+
 /*
  *		connectOptions2
  *
@@ -1020,6 +1072,7 @@ static bool
 connectOptions2(PGconn *conn)
 {
 	int			i;
+	int			loadbalancehosts = loadBalance(conn);
 
 	/*
 	 * Allocate memory for details about each host to which we might possibly
@@ -1167,6 +1220,36 @@ connectOptions2(PGconn *conn)
 		}
 	}
 
+	if (loadbalancehosts < 0)
+	{
+		appendPQExpBufferStr(&conn->errorMessage,
+							 libpq_gettext("loadbalance parameter must be an integer\n"));
+		return false;
+	}
+
+	if (loadbalancehosts)
+	{
+		if (!libpq_prng_init(conn))
+		{
+			return false;
+		}
+
+		/*
+		 * Shuffle connhost with a Durstenfeld/Knuth version of the
+		 * Fisher-Yates shuffle. Source:
+		 * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
+		 */
+		for (i = conn->nconnhost - 1; i > 0; i--)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
+
 	/*
 	 * If user name was not given, fetch it.  (Most likely, the fetch will
 	 * fail, since the only way we get here is if pg_fe_getauthname() failed
@@ -1745,6 +1828,27 @@ connectFailureMessage(PGconn *conn, int errorno)
 							 libpq_gettext("\tIs the server running on that host and accepting TCP/IP connections?\n"));
 }
 
+/*
+ * Should we load balance across hosts? Returns 1 if yes, 0 if no, and -1 if
+ * conn->loadbalance is set to a value which is not parseable as an integer.
+ */
+static int
+loadBalance(PGconn *conn)
+{
+	char	   *ep;
+	int			val;
+
+	if (conn->loadbalance == NULL)
+	{
+		return 0;
+	}
+	val = strtol(conn->loadbalance, &ep, 10);
+	if (*ep)
+		return -1;
+	return val != 0 ? 1 : 0;
+}
+
+
 /*
  * Should we use keepalives?  Returns 1 if yes, 0 if no, and -1 if
  * conn->keepalives is set to a value which is not parseable as an
@@ -2102,7 +2206,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2146,11 +2250,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2298,9 +2402,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2313,6 +2417,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2353,7 +2458,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2378,8 +2483,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					appendPQExpBuffer(&conn->errorMessage,
 									  libpq_gettext("could not translate host name \"%s\" to address: %s\n"),
@@ -2391,8 +2496,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					appendPQExpBuffer(&conn->errorMessage,
 									  libpq_gettext("could not parse network address \"%s\": %s\n"),
@@ -2402,7 +2507,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2418,8 +2523,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					appendPQExpBuffer(&conn->errorMessage,
 									  libpq_gettext("could not translate Unix-domain socket path \"%s\" to address: %s\n"),
@@ -2429,8 +2534,15 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		if (!store_conn_addrinfo(conn, addrlist))
+		{
+			pg_freeaddrinfo_all(hint.ai_family, addrlist);
+			appendPQExpBufferStr(&conn->errorMessage,
+								 libpq_gettext("out of memory\n"));
+			goto error_return;
+		}
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2487,30 +2599,29 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2526,7 +2637,7 @@ keep_going:						/* We will come back to here until there is
 						conn->connip = strdup(host_addr);
 
 					/* Try to create the socket */
-					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
+					conn->sock = socket(addr_cur->family, SOCK_STREAM, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2537,7 +2648,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2564,7 +2675,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2593,7 +2704,7 @@ keep_going:						/* We will come back to here until there is
 					}
 #endif							/* F_SETFD */
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2687,8 +2798,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4056,6 +4167,8 @@ freePGconn(PGconn *conn)
 	}
 	free(conn->pgpassfile);
 	free(conn->channel_binding);
+	free(conn->loadbalance);
+	free(conn->randomseed);
 	free(conn->keepalives);
 	free(conn->keepalives_idle);
 	free(conn->keepalives_interval);
@@ -4092,6 +4205,63 @@ freePGconn(PGconn *conn)
 	free(conn);
 }
 
+
+/*
+ * Copies over the AddrInfos from addrlist to the PGconn.
+ */
+static bool
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+	{
+		return false;
+	}
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	if (loadBalance(conn))
+	{
+		/*
+		 * Shuffle addr with a Durstenfeld/Knuth version of the Fisher-Yates
+		 * shuffle. Source:
+		 * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
+		 *
+		 * We don't need to initialize conn->prng_state here, because that
+		 * already happened in connectOptions2.
+		 */
+		for (int i = conn->naddr - 1; i > 0; i--)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			AddrInfo	temp = conn->addr[j];
+
+			conn->addr[j] = conn->addr[i];
+			conn->addr[i] = temp;
+		}
+	}
+	return true;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4099,11 +4269,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index c75ed63a2c..17f2c214d4 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -82,6 +82,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -373,6 +375,8 @@ struct pg_conn
 	char	   *pgpassfile;		/* path to a file containing password(s) */
 	char	   *channel_binding;	/* channel binding mode
 									 * (require,prefer,disable) */
+	char	   *loadbalance;	/* load balance over hosts */
+	char	   *randomseed;		/* seed for randomization of load balancing */
 	char	   *keepalives;		/* use TCP keepalives? */
 	char	   *keepalives_idle;	/* time between TCP keepalives */
 	char	   *keepalives_interval;	/* time between TCP keepalive
@@ -461,8 +465,10 @@ struct pg_conn
 	PGTargetServerType target_server_type;	/* desired session properties */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
+	int			naddr;			/* number of addrs returned by getaddrinfo */
+	int			whichaddr;		/* the addr currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	int			addrlist_family;	/* needed to know how to free addrlist */
 	bool		send_appname;	/* okay to send application_name? */
 
@@ -477,6 +483,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index bc047e00d6..62850715e9 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -100,6 +100,7 @@ tests += {
     'tests': [
       't/001_uri.pl',
       't/002_api.pl',
+      't/003_loadbalance.pl',
     ],
     'env': {'with_ssl': get_option('ssl')},
   },
diff --git a/src/interfaces/libpq/t/003_loadbalance.pl b/src/interfaces/libpq/t/003_loadbalance.pl
new file mode 100644
index 0000000000..4f879e8de7
--- /dev/null
+++ b/src/interfaces/libpq/t/003_loadbalance.pl
@@ -0,0 +1,134 @@
+# Copyright (c) 2022, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use File::Spec::Functions 'catfile';
+use Test::More;
+
+# To test load balancing when there's a single host that resolves to different
+# IPs we use addresess 127.0.0.2 and 127.0.0.3. Linux and Windows allow binding
+# to these addresess by default, but other OSes don't. We skip these tests on
+# platforms that don't support this.
+my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os;
+
+if ($can_bind_to_127_0_0_2)
+{
+	$PostgreSQL::Test::Cluster::use_tcp = 1;
+	$PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1';
+}
+my $port = PostgreSQL::Test::Cluster::get_free_port();
+my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port);
+my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+my $host = $node1->host . ',' . $node2->host . ',' . $node3->host;
+my $portlist = "$port,$port,$port";
+
+$node1->connect_ok("host=$host port=$portlist load_balance_hosts=1 random_seed=123",
+	"seed 123 selects node 1 first",
+	sql => "SELECT 'connect1'",
+	log_like => [qr/statement: SELECT 'connect1'/]);
+
+$node2->connect_ok("host=$host port=$portlist load_balance_hosts=1 random_seed=123",
+	"seed 123 does not select node 2 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$host port=$portlist load_balance_hosts=1 random_seed=123",
+	"seed 123 does not select node 3 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$host port=$portlist load_balance_hosts=1 random_seed=42",
+	"seed 42 selects node 3 first",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+$node1->connect_ok("host=$host port=$portlist load_balance_hosts=1 random_seed=42",
+	"seed 42 does not select node 1 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node2->connect_ok("host=$host port=$portlist load_balance_hosts=1 random_seed=42",
+	"seed 42 does not select node 2 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node3->stop();
+
+$node1->connect_ok("host=$host port=$portlist load_balance_hosts=1 random_seed=42",
+	"seed 42 does select node 1 second",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+$node2->connect_ok("host=$host port=$portlist load_balance_hosts=1 random_seed=42",
+	"seed 42 does not select node 2 second",
+	sql => "SELECT 'connect3'",
+	log_unlike => [qr/statement: SELECT 'connect3'/]);
+
+$node3->start();
+
+if ($can_bind_to_127_0_0_2) {
+	# To make the following tests run and pass add the following content to your
+	# hosts file:
+	# 127.0.0.1 pg-loadbalancetest
+	# 127.0.0.2 pg-loadbalancetest
+	# 127.0.0.3 pg-loadbalancetest
+	#
+	# If the hosts file doesn't contain the hostname we expect, then we skip
+	# these tests. In CI we set up these specific rules in the hosts files to
+	# test this load balancing behaviour. But users running our test suite
+	# locally should not be forced to do so to make all the tests pass.
+	my $hosts_path;
+	if ($windows_os) {
+		$hosts_path = 'c:\Windows\System32\Drivers\etc\hosts';
+	}
+	else
+	{
+		$hosts_path = '/etc/hosts';
+	}
+
+	my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path);
+
+	if ($hosts_content =~ m/pg-loadbalancetest/) {
+		$node2->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44",
+			"seed 44 selects node 2 first",
+			sql => "SELECT 'connect4'",
+			log_like => [qr/statement: SELECT 'connect4'/]);
+
+		$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44",
+			"seed 44 does not select node 1 first",
+			sql => "SELECT 'connect4'",
+			log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+		$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44",
+			"seed 44 does not select node 3 first",
+			sql => "SELECT 'connect4'",
+			log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+		$node2->stop();
+
+		$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44",
+			"seed 44 does select node 1 second",
+			sql => "SELECT 'connect5'",
+			log_like => [qr/statement: SELECT 'connect5'/]);
+
+		$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44",
+			"seed 44 does not select node 3 second",
+			sql => "SELECT 'connect5'",
+			log_unlike => [qr/statement: SELECT 'connect5'/]);
+	}
+}
+
+done_testing();
-- 
2.34.1

From 6e20bb223012b666161521b5e7249c066467a5f3 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <github-tech@jeltef.nl>
Date: Mon, 12 Sep 2022 09:44:06 +0200
Subject: [PATCH v5] Support load balancing in libpq

Load balancing connections across multiple read replicas is a pretty
common way of scaling out read queries. There are two main ways of doing
so, both with their own advantages and disadvantages:
1. Load balancing at the client level
2. Load balancing by connecting to an intermediary load balancer

Both JBDC (Java) and Npgsql (C#) already support client level load
balancing (option #1). This patch implements client level load balancing
for libpq as well. To stay consistent with the JDBC and Npgsql part of
the  ecosystem, a similar implementation and name for the option are
used. It contains two levels of load balancing:
1. The given hosts are randomly shuffled, before resolving them
    one-by-one.
2. Once a host its addresses get resolved, those addresses are shuffled,
    before trying to connect to them one-by-one.
---
 .cirrus.yml                               |  14 ++
 doc/src/sgml/libpq.sgml                   |  48 +++++
 src/include/libpq/pqcomm.h                |   6 +
 src/interfaces/libpq/fe-connect.c         | 231 +++++++++++++++++++---
 src/interfaces/libpq/libpq-int.h          |  12 +-
 src/interfaces/libpq/meson.build          |   1 +
 src/interfaces/libpq/t/003_loadbalance.pl | 167 ++++++++++++++++
 7 files changed, 446 insertions(+), 33 deletions(-)
 create mode 100644 src/interfaces/libpq/t/003_loadbalance.pl

diff --git a/.cirrus.yml b/.cirrus.yml
index f31923333e..54c3c00e1b 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -293,6 +293,14 @@ task:
     mkdir -m 770 /tmp/cores
     chown root:postgres /tmp/cores
     sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core'
+
+  setup_hosts_file_script: |
+    cat >> /etc/hosts <<-EOF
+      127.0.0.1 pg-loadbalancetest
+      127.0.0.2 pg-loadbalancetest
+      127.0.0.3 pg-loadbalancetest
+    EOF
+
   setup_additional_packages_script: |
     #apt-get update
     #DEBIAN_FRONTEND=noninteractive apt-get -y install ...
@@ -540,6 +548,12 @@ task:
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
+  setup_hosts_file_script: |
+    echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    type c:\Windows\System32\Drivers\etc\hosts
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index f9558dec3b..6ce7a0c9cc 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1316,6 +1316,54 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
       </listitem>
      </varlistentry>
 
+     <varlistentry id="libpq-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls whether the client load balances connections across hosts and
+        adresses. The default value is 0, meaning off, this means that hosts are
+        tried in order they are provided and addresses are tried in the order
+        they are received from DNS or a hosts file. If this value is set to 1,
+        meaning on, the hosts and addresses that they resolve to are tried in
+        random order. Subsequent queries once connected will still be sent to
+        the same server. Setting this to 1, is mostly useful when opening
+        multiple connections at the same time, possibly from different machines.
+        This way connections can be load balanced across multiple Postgres
+        servers.
+       </para>
+       <para>
+        When providing multiple hosts, these hosts are resolved in random order.
+        Then if that host resolves to multiple addresses, these addresses are
+        connected to in random order. Only once all addresses for a single host
+        have been tried, the addresses for the next random host will be
+        resolved. This behaviour can lead to non-uniform address selection in
+        certain cases. Such as when not all hosts resolve to the same number of
+        addresses, or when multiple hosts resolve to the same address. So if you
+        want uniform load balancing, this is something to keep in mind. However,
+        non-uniform load balancing also has usecases, e.g. providing the
+        hostname of a larger server multiple times in the host string so it gets
+        more requests.
+       </para>
+       <para>
+        When using this setting it's recommended to also configure a reasonable
+        value for <xref linkend="libpq-connect-connect-timeout"/>. Because then,
+        if one of the nodes that are used for load balancing is not responding,
+        a new node will be tried.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-random-seed" xreflabel="random_seed">
+      <term><literal>random_seed</literal></term>
+      <listitem>
+       <para>
+        Sets the random seed that is used by <xref linkend="libpq-load-balance-hosts"/>
+        to randomize the host order. This option is mostly useful when running
+        tests that require a stable random order.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="libpq-keepalives" xreflabel="keepalives">
       <term><literal>keepalives</literal></term>
       <listitem>
diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index fcf68df39b..39e93b1392 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+}			AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index f88d672c6c..b4d3613713 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -241,6 +241,14 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Fallback-Application-Name", "", 64,
 	offsetof(struct pg_conn, fbappname)},
 
+	{"load_balance_hosts", NULL, NULL, NULL,
+		"Load-Balance", "", 1,	/* should be just '0' or '1' */
+	offsetof(struct pg_conn, loadbalance)},
+
+	{"random_seed", NULL, NULL, NULL,
+		"Random-Seed", "", 10,	/* strlen(INT32_MAX) == 10 */
+	offsetof(struct pg_conn, randomseed)},
+
 	{"keepalives", NULL, NULL, NULL,
 		"TCP-Keepalives", "", 1,	/* should be just '0' or '1' */
 	offsetof(struct pg_conn, keepalives)},
@@ -379,6 +387,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *connstr,
@@ -424,6 +433,9 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static int	loadBalance(PGconn *conn);
+static bool parse_int_param(const char *value, int *result, PGconn *conn,
+							const char *context);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1007,6 +1019,46 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on timestamp and PID.
+ */
+static bool
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(conn->randomseed))
+	{
+		int			rseed;
+
+		if (!parse_int_param(conn->randomseed, &rseed, conn, "random_seed"))
+		{
+			return false;
+		};
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	else if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		time_t		now = time(NULL);
+
+		/*
+		 * Since PIDs and timestamps tend to change more frequently in their
+		 * least significant bits, shift the timestamp left to allow a larger
+		 * total number of seeds in a given time period.  Since that would
+		 * leave only 20 bits of the timestamp that cycle every ~1 second,
+		 * also mix in some higher bits.
+		 */
+		rseed = ((uint64) getpid()) ^
+			((uint64) now << 12) ^
+			((uint64) now >> 20);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	return true;
+}
+
+
 /*
  *		connectOptions2
  *
@@ -1019,6 +1071,7 @@ static bool
 connectOptions2(PGconn *conn)
 {
 	int			i;
+	int			loadbalancehosts = loadBalance(conn);
 
 	/*
 	 * Allocate memory for details about each host to which we might possibly
@@ -1164,6 +1217,36 @@ connectOptions2(PGconn *conn)
 		}
 	}
 
+	if (loadbalancehosts < 0)
+	{
+		appendPQExpBufferStr(&conn->errorMessage,
+							 libpq_gettext("loadbalance parameter must be an integer\n"));
+		return false;
+	}
+
+	if (loadbalancehosts)
+	{
+		if (!libpq_prng_init(conn))
+		{
+			return false;
+		}
+
+		/*
+		 * Shuffle connhost with a Durstenfeld/Knuth version of the
+		 * Fisher-Yates shuffle. Source:
+		 * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
+		 */
+		for (i = conn->nconnhost - 1; i > 0; i--)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
+
 	/*
 	 * If user name was not given, fetch it.  (Most likely, the fetch will
 	 * fail, since the only way we get here is if pg_fe_getauthname() failed
@@ -1726,6 +1809,27 @@ connectFailureMessage(PGconn *conn, int errorno)
 		libpq_append_conn_error(conn, "\tIs the server running on that host and accepting TCP/IP connections?");
 }
 
+/*
+ * Should we load balance across hosts? Returns 1 if yes, 0 if no, and -1 if
+ * conn->loadbalance is set to a value which is not parseable as an integer.
+ */
+static int
+loadBalance(PGconn *conn)
+{
+	char	   *ep;
+	int			val;
+
+	if (conn->loadbalance == NULL)
+	{
+		return 0;
+	}
+	val = strtol(conn->loadbalance, &ep, 10);
+	if (*ep)
+		return -1;
+	return val != 0 ? 1 : 0;
+}
+
+
 /*
  * Should we use keepalives?  Returns 1 if yes, 0 if no, and -1 if
  * conn->keepalives is set to a value which is not parseable as an
@@ -2077,7 +2181,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2121,11 +2225,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2272,9 +2376,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2287,6 +2391,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2327,7 +2432,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2350,8 +2455,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
 									   ch->host, gai_strerror(ret));
@@ -2362,8 +2467,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
 									   ch->hostaddr, gai_strerror(ret));
@@ -2372,7 +2477,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2387,8 +2492,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
 									   portstr, gai_strerror(ret));
@@ -2397,8 +2502,15 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		if (!store_conn_addrinfo(conn, addrlist))
+		{
+			pg_freeaddrinfo_all(hint.ai_family, addrlist);
+			appendPQExpBufferStr(&conn->errorMessage,
+								 libpq_gettext("out of memory\n"));
+			goto error_return;
+		}
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2455,30 +2567,29 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2494,7 +2605,7 @@ keep_going:						/* We will come back to here until there is
 						conn->connip = strdup(host_addr);
 
 					/* Try to create the socket */
-					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
+					conn->sock = socket(addr_cur->family, SOCK_STREAM, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2505,7 +2616,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2531,7 +2642,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2558,7 +2669,7 @@ keep_going:						/* We will come back to here until there is
 					}
 #endif							/* F_SETFD */
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2650,8 +2761,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4005,6 +4116,8 @@ freePGconn(PGconn *conn)
 	}
 	free(conn->pgpassfile);
 	free(conn->channel_binding);
+	free(conn->loadbalance);
+	free(conn->randomseed);
 	free(conn->keepalives);
 	free(conn->keepalives_idle);
 	free(conn->keepalives_interval);
@@ -4041,6 +4154,63 @@ freePGconn(PGconn *conn)
 	free(conn);
 }
 
+
+/*
+ * Copies over the AddrInfos from addrlist to the PGconn.
+ */
+static bool
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+	{
+		return false;
+	}
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	if (loadBalance(conn))
+	{
+		/*
+		 * Shuffle addr with a Durstenfeld/Knuth version of the Fisher-Yates
+		 * shuffle. Source:
+		 * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
+		 *
+		 * We don't need to initialize conn->prng_state here, because that
+		 * already happened in connectOptions2.
+		 */
+		for (int i = conn->naddr - 1; i > 0; i--)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			AddrInfo	temp = conn->addr[j];
+
+			conn->addr[j] = conn->addr[i];
+			conn->addr[i] = temp;
+		}
+	}
+	return true;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4048,11 +4218,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 512762f999..76ee988038 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -82,6 +82,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -373,6 +375,8 @@ struct pg_conn
 	char	   *pgpassfile;		/* path to a file containing password(s) */
 	char	   *channel_binding;	/* channel binding mode
 									 * (require,prefer,disable) */
+	char	   *loadbalance;	/* load balance over hosts */
+	char	   *randomseed;		/* seed for randomization of load balancing */
 	char	   *keepalives;		/* use TCP keepalives? */
 	char	   *keepalives_idle;	/* time between TCP keepalives */
 	char	   *keepalives_interval;	/* time between TCP keepalive
@@ -461,8 +465,10 @@ struct pg_conn
 	PGTargetServerType target_server_type;	/* desired session properties */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
+	int			naddr;			/* number of addrs returned by getaddrinfo */
+	int			whichaddr;		/* the addr currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	int			addrlist_family;	/* needed to know how to free addrlist */
 	bool		send_appname;	/* okay to send application_name? */
 
@@ -477,6 +483,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index 8e696f1183..8026398518 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -114,6 +114,7 @@ tests += {
     'tests': [
       't/001_uri.pl',
       't/002_api.pl',
+      't/003_loadbalance.pl',
     ],
     'env': {'with_ssl': get_option('ssl')},
   },
diff --git a/src/interfaces/libpq/t/003_loadbalance.pl b/src/interfaces/libpq/t/003_loadbalance.pl
new file mode 100644
index 0000000000..07eddbe9cc
--- /dev/null
+++ b/src/interfaces/libpq/t/003_loadbalance.pl
@@ -0,0 +1,167 @@
+# Copyright (c) 2022, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use File::Spec::Functions 'catfile';
+use Test::More;
+
+# This tests two different methods of load balancing from libpq
+# 1. Load balancing by providing multiple host and port combinations in the
+#    libpq connection string.
+# 2. By using a hosts file where hostname maps to multiple different IP
+#    addresses. Regular Postgres users wouldn't usually use such a host file,
+#    but this is the easiest way to immitate behaviour of a DNS server that
+#    returns multiple IP addresses for the same DNS record.
+#
+# Testing method 1 is supported on all platforms and works out of the box. But
+# testing method 2 has some more requirements, both on the platform and on the
+# initial setup. If any of these requirements are not met, then method 2 is
+# simply not tested.
+#
+# The requirements to test method 2 are as follows:
+# 1. Windows or Linux should be used.
+# 2. The OS hosts file at /etc/hosts or c:\Windows\System32\Drivers\etc\hosts
+#    should contain the following contents:
+#
+# 127.0.0.1 pg-loadbalancetest
+# 127.0.0.2 pg-loadbalancetest
+# 127.0.0.3 pg-loadbalancetest
+#
+#
+# Windows or Linux are required to test method 2 because these OSes allow
+# binding to 127.0.0.2 and 127.0.0.3 addresess by default, but other OSes
+# don't. We need to bind to different IP addresses, so that we can use these
+# different IP addresses in the hosts file.
+#
+# The hosts file needs to be prepared before running this test. We don't do it
+# on the fly, because it requires root permissions to change the hosts file. In
+# CI we set up the previously mentioned rules in the hosts file, so that this
+# load balancing method is tested.
+
+
+# Cluster setup which is shared for testing both load balancing methods
+my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os;
+
+if ($can_bind_to_127_0_0_2)
+{
+	$PostgreSQL::Test::Cluster::use_tcp = 1;
+	$PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1';
+}
+my $port = PostgreSQL::Test::Cluster::get_free_port();
+my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port);
+my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# Start the tests for load balancing method 1
+my $hostlist = $node1->host . ',' . $node2->host . ',' . $node3->host;
+my $portlist = "$port,$port,$port";
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=123",
+	"seed 123 selects node 1 first",
+	sql => "SELECT 'connect1'",
+	log_like => [qr/statement: SELECT 'connect1'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=123",
+	"seed 123 does not select node 2 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=123",
+	"seed 123 does not select node 3 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=42",
+	"seed 42 selects node 3 first",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=42",
+	"seed 42 does not select node 1 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=42",
+	"seed 42 does not select node 2 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node3->stop();
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=42",
+	"seed 42 does select node 1 second",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=42",
+	"seed 42 does not select node 2 second",
+	sql => "SELECT 'connect3'",
+	log_unlike => [qr/statement: SELECT 'connect3'/]);
+
+$node3->start();
+
+# Checks for the requirements for testing load balancing method 2
+if (!$can_bind_to_127_0_0_2) {
+	# The OS requirement is not met
+	done_testing();
+	exit;
+}
+
+my $hosts_path;
+if ($windows_os) {
+	$hosts_path = 'c:\Windows\System32\Drivers\etc\hosts';
+}
+else
+{
+	$hosts_path = '/etc/hosts';
+}
+
+my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path);
+
+if ($hosts_content !~ m/pg-loadbalancetest/) {
+	# Host file is not prepared for this test
+	done_testing();
+	exit;
+}
+
+# Start the tests for load balancing method 2
+$node2->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44",
+	"seed 44 selects node 2 first",
+	sql => "SELECT 'connect4'",
+	log_like => [qr/statement: SELECT 'connect4'/]);
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44",
+	"seed 44 does not select node 1 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44",
+	"seed 44 does not select node 3 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node2->stop();
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44",
+	"seed 44 does select node 1 second",
+	sql => "SELECT 'connect5'",
+	log_like => [qr/statement: SELECT 'connect5'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44",
+	"seed 44 does not select node 3 second",
+	sql => "SELECT 'connect5'",
+	log_unlike => [qr/statement: SELECT 'connect5'/]);
+
+done_testing();
-- 
2.34.1

From beb005477c16af285df7fc068bfc2def70e5acf8 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 30 Nov 2022 10:07:19 +0100
Subject: [PATCH v6 1/2] libpq: Run pgindent after a9e9a9f32b3

It seems that pgindent was not run after the error handling refactor in
commit a9e9a9f32b35edf129c88e8b929ef223f8511f59. This fixes that and
also addresses a few other things pgindent wanted to change in libpq.
---
 src/interfaces/libpq/fe-auth-scram.c     |   2 +-
 src/interfaces/libpq/fe-auth.c           |   8 +-
 src/interfaces/libpq/fe-connect.c        | 124 +++++++++++------------
 src/interfaces/libpq/fe-exec.c           |  16 +--
 src/interfaces/libpq/fe-lobj.c           |  42 ++++----
 src/interfaces/libpq/fe-misc.c           |  10 +-
 src/interfaces/libpq/fe-protocol3.c      |   2 +-
 src/interfaces/libpq/fe-secure-common.c  |   6 +-
 src/interfaces/libpq/fe-secure-gssapi.c  |  12 +--
 src/interfaces/libpq/fe-secure-openssl.c |  64 ++++++------
 src/interfaces/libpq/fe-secure.c         |   8 +-
 src/interfaces/libpq/libpq-int.h         |   4 +-
 12 files changed, 149 insertions(+), 149 deletions(-)

diff --git a/src/interfaces/libpq/fe-auth-scram.c b/src/interfaces/libpq/fe-auth-scram.c
index 9c42ea4f81..12c3d0bc33 100644
--- a/src/interfaces/libpq/fe-auth-scram.c
+++ b/src/interfaces/libpq/fe-auth-scram.c
@@ -716,7 +716,7 @@ read_server_final_message(fe_scram_state *state, char *input)
 			return false;
 		}
 		libpq_append_conn_error(conn, "error received from server in SCRAM exchange: %s",
-						   errmsg);
+								errmsg);
 		return false;
 	}
 
diff --git a/src/interfaces/libpq/fe-auth.c b/src/interfaces/libpq/fe-auth.c
index 9afc6f19b9..ab454e6cd0 100644
--- a/src/interfaces/libpq/fe-auth.c
+++ b/src/interfaces/libpq/fe-auth.c
@@ -73,7 +73,7 @@ pg_GSS_continue(PGconn *conn, int payloadlen)
 		if (!ginbuf.value)
 		{
 			libpq_append_conn_error(conn, "out of memory allocating GSSAPI buffer (%d)",
-							  payloadlen);
+									payloadlen);
 			return STATUS_ERROR;
 		}
 		if (pqGetnchar(ginbuf.value, payloadlen, conn))
@@ -223,7 +223,7 @@ pg_SSPI_continue(PGconn *conn, int payloadlen)
 		if (!inputbuf)
 		{
 			libpq_append_conn_error(conn, "out of memory allocating SSPI buffer (%d)",
-							  payloadlen);
+									payloadlen);
 			return STATUS_ERROR;
 		}
 		if (pqGetnchar(inputbuf, payloadlen, conn))
@@ -623,7 +623,7 @@ pg_SASL_continue(PGconn *conn, int payloadlen, bool final)
 	if (!challenge)
 	{
 		libpq_append_conn_error(conn, "out of memory allocating SASL buffer (%d)",
-						  payloadlen);
+								payloadlen);
 		return STATUS_ERROR;
 	}
 
@@ -1277,7 +1277,7 @@ PQencryptPasswordConn(PGconn *conn, const char *passwd, const char *user,
 	else
 	{
 		libpq_append_conn_error(conn, "unrecognized password encryption algorithm \"%s\"",
-						  algorithm);
+								algorithm);
 		return NULL;
 	}
 
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 50b5df3490..773e9e1f3a 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -1079,7 +1079,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "could not match %d host names to %d hostaddr values",
-							   count_comma_separated_elems(conn->pghost), conn->nconnhost);
+									count_comma_separated_elems(conn->pghost), conn->nconnhost);
 			return false;
 		}
 	}
@@ -1159,7 +1159,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "could not match %d port numbers to %d hosts",
-							   count_comma_separated_elems(conn->pgport), conn->nconnhost);
+									count_comma_separated_elems(conn->pgport), conn->nconnhost);
 			return false;
 		}
 	}
@@ -1248,7 +1248,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "channel_binding", conn->channel_binding);
+									"channel_binding", conn->channel_binding);
 			return false;
 		}
 	}
@@ -1273,7 +1273,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "sslmode", conn->sslmode);
+									"sslmode", conn->sslmode);
 			return false;
 		}
 
@@ -1293,7 +1293,7 @@ connectOptions2(PGconn *conn)
 			case 'v':			/* "verify-ca" or "verify-full" */
 				conn->status = CONNECTION_BAD;
 				libpq_append_conn_error(conn, "sslmode value \"%s\" invalid when SSL support is not compiled in",
-								   conn->sslmode);
+										conn->sslmode);
 				return false;
 		}
 #endif
@@ -1313,16 +1313,16 @@ connectOptions2(PGconn *conn)
 	{
 		conn->status = CONNECTION_BAD;
 		libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-						   "ssl_min_protocol_version",
-						   conn->ssl_min_protocol_version);
+								"ssl_min_protocol_version",
+								conn->ssl_min_protocol_version);
 		return false;
 	}
 	if (!sslVerifyProtocolVersion(conn->ssl_max_protocol_version))
 	{
 		conn->status = CONNECTION_BAD;
 		libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-						   "ssl_max_protocol_version",
-						   conn->ssl_max_protocol_version);
+								"ssl_max_protocol_version",
+								conn->ssl_max_protocol_version);
 		return false;
 	}
 
@@ -1359,7 +1359,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "gssencmode value \"%s\" invalid when GSSAPI support is not compiled in",
-							   conn->gssencmode);
+									conn->gssencmode);
 			return false;
 		}
 #endif
@@ -1392,8 +1392,8 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "target_session_attrs",
-							   conn->target_session_attrs);
+									"target_session_attrs",
+									conn->target_session_attrs);
 			return false;
 		}
 	}
@@ -1609,7 +1609,7 @@ connectNoDelay(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "could not set socket to TCP no delay mode: %s",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1787,7 +1787,7 @@ parse_int_param(const char *value, int *result, PGconn *conn,
 
 error:
 	libpq_append_conn_error(conn, "invalid integer value \"%s\" for connection option \"%s\"",
-					   value, context);
+							value, context);
 	return false;
 }
 
@@ -1816,9 +1816,9 @@ setKeepalivesIdle(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   PG_TCP_KEEPALIVE_IDLE_STR,
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								PG_TCP_KEEPALIVE_IDLE_STR,
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1850,9 +1850,9 @@ setKeepalivesInterval(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_KEEPINTVL",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_KEEPINTVL",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1885,9 +1885,9 @@ setKeepalivesCount(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_KEEPCNT",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_KEEPCNT",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1949,8 +1949,8 @@ prepKeepalivesWin32(PGconn *conn)
 	if (!setKeepalivesWin32(conn->sock, idle, interval))
 	{
 		libpq_append_conn_error(conn, "%s(%s) failed: error code %d",
-						  "WSAIoctl", "SIO_KEEPALIVE_VALS",
-						  WSAGetLastError());
+								"WSAIoctl", "SIO_KEEPALIVE_VALS",
+								WSAGetLastError());
 		return 0;
 	}
 	return 1;
@@ -1983,9 +1983,9 @@ setTCPUserTimeout(PGconn *conn)
 		char		sebuf[256];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_USER_TIMEOUT",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_USER_TIMEOUT",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -2354,7 +2354,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
-									   ch->host, gai_strerror(ret));
+											ch->host, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2366,7 +2366,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
-									   ch->hostaddr, gai_strerror(ret));
+											ch->hostaddr, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2377,8 +2377,8 @@ keep_going:						/* We will come back to here until there is
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
 					libpq_append_conn_error(conn, "Unix-domain socket path \"%s\" is too long (maximum %d bytes)",
-									   portstr,
-									   (int) (UNIXSOCK_PATH_BUFLEN - 1));
+											portstr,
+											(int) (UNIXSOCK_PATH_BUFLEN - 1));
 					goto keep_going;
 				}
 
@@ -2391,7 +2391,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
-									   portstr, gai_strerror(ret));
+											portstr, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2513,7 +2513,7 @@ keep_going:						/* We will come back to here until there is
 						}
 						emitHostIdentityInfo(conn, host_addr);
 						libpq_append_conn_error(conn, "could not create socket: %s",
-										   SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2543,7 +2543,7 @@ keep_going:						/* We will come back to here until there is
 					if (!pg_set_noblock(conn->sock))
 					{
 						libpq_append_conn_error(conn, "could not set socket to nonblocking mode: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						conn->try_next_addr = true;
 						goto keep_going;
 					}
@@ -2552,7 +2552,7 @@ keep_going:						/* We will come back to here until there is
 					if (fcntl(conn->sock, F_SETFD, FD_CLOEXEC) == -1)
 					{
 						libpq_append_conn_error(conn, "could not set socket to close-on-exec mode: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						conn->try_next_addr = true;
 						goto keep_going;
 					}
@@ -2581,9 +2581,9 @@ keep_going:						/* We will come back to here until there is
 											(char *) &on, sizeof(on)) < 0)
 						{
 							libpq_append_conn_error(conn, "%s(%s) failed: %s",
-											   "setsockopt",
-											   "SO_KEEPALIVE",
-											   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+													"setsockopt",
+													"SO_KEEPALIVE",
+													SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 							err = 1;
 						}
 						else if (!setKeepalivesIdle(conn)
@@ -2708,7 +2708,7 @@ keep_going:						/* We will come back to here until there is
 							   (char *) &optval, &optlen) == -1)
 				{
 					libpq_append_conn_error(conn, "could not get socket error status: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					goto error_return;
 				}
 				else if (optval != 0)
@@ -2735,7 +2735,7 @@ keep_going:						/* We will come back to here until there is
 								&conn->laddr.salen) < 0)
 				{
 					libpq_append_conn_error(conn, "could not get client address from socket: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					goto error_return;
 				}
 
@@ -2775,7 +2775,7 @@ keep_going:						/* We will come back to here until there is
 							libpq_append_conn_error(conn, "requirepeer parameter is not supported on this platform");
 						else
 							libpq_append_conn_error(conn, "could not get peer credentials: %s",
-											   strerror_r(errno, sebuf, sizeof(sebuf)));
+													strerror_r(errno, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2788,7 +2788,7 @@ keep_going:						/* We will come back to here until there is
 					if (strcmp(remote_username, conn->requirepeer) != 0)
 					{
 						libpq_append_conn_error(conn, "requirepeer specifies \"%s\", but actual peer user name is \"%s\"",
-										   conn->requirepeer, remote_username);
+												conn->requirepeer, remote_username);
 						free(remote_username);
 						goto error_return;
 					}
@@ -2829,7 +2829,7 @@ keep_going:						/* We will come back to here until there is
 					if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
 					{
 						libpq_append_conn_error(conn, "could not send GSSAPI negotiation packet: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2840,7 +2840,7 @@ keep_going:						/* We will come back to here until there is
 				else if (!conn->gctx && conn->gssencmode[0] == 'r')
 				{
 					libpq_append_conn_error(conn,
-									   "GSSAPI encryption required but was impossible (possibly no credential cache, no server support, or using a local socket)");
+											"GSSAPI encryption required but was impossible (possibly no credential cache, no server support, or using a local socket)");
 					goto error_return;
 				}
 #endif
@@ -2882,7 +2882,7 @@ keep_going:						/* We will come back to here until there is
 					if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
 					{
 						libpq_append_conn_error(conn, "could not send SSL negotiation packet: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 					/* Ok, wait for response */
@@ -2911,7 +2911,7 @@ keep_going:						/* We will come back to here until there is
 				if (pqPacketSend(conn, 0, startpacket, packetlen) != STATUS_OK)
 				{
 					libpq_append_conn_error(conn, "could not send startup packet: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					free(startpacket);
 					goto error_return;
 				}
@@ -3012,7 +3012,7 @@ keep_going:						/* We will come back to here until there is
 					else
 					{
 						libpq_append_conn_error(conn, "received invalid response to SSL negotiation: %c",
-										   SSLok);
+												SSLok);
 						goto error_return;
 					}
 				}
@@ -3123,7 +3123,7 @@ keep_going:						/* We will come back to here until there is
 					else if (gss_ok != 'G')
 					{
 						libpq_append_conn_error(conn, "received invalid response to GSSAPI negotiation: %c",
-										   gss_ok);
+												gss_ok);
 						goto error_return;
 					}
 				}
@@ -3201,7 +3201,7 @@ keep_going:						/* We will come back to here until there is
 				if (!(beresp == 'R' || beresp == 'v' || beresp == 'E'))
 				{
 					libpq_append_conn_error(conn, "expected authentication request from server, but received %c",
-									   beresp);
+											beresp);
 					goto error_return;
 				}
 
@@ -3216,17 +3216,17 @@ keep_going:						/* We will come back to here until there is
 				 * Try to validate message length before using it.
 				 * Authentication requests can't be very large, although GSS
 				 * auth requests may not be that small.  Same for
-				 * NegotiateProtocolVersion.  Errors can be a
-				 * little larger, but not huge.  If we see a large apparent
-				 * length in an error, it means we're really talking to a
-				 * pre-3.0-protocol server; cope.  (Before version 14, the
-				 * server also used the old protocol for errors that happened
-				 * before processing the startup packet.)
+				 * NegotiateProtocolVersion.  Errors can be a little larger,
+				 * but not huge.  If we see a large apparent length in an
+				 * error, it means we're really talking to a pre-3.0-protocol
+				 * server; cope.  (Before version 14, the server also used the
+				 * old protocol for errors that happened before processing the
+				 * startup packet.)
 				 */
 				if ((beresp == 'R' || beresp == 'v') && (msgLength < 8 || msgLength > 2000))
 				{
 					libpq_append_conn_error(conn, "expected authentication request from server, but received %c",
-									   beresp);
+											beresp);
 					goto error_return;
 				}
 
@@ -3705,7 +3705,7 @@ keep_going:						/* We will come back to here until there is
 
 				/* Append error report to conn->errorMessage. */
 				libpq_append_conn_error(conn, "\"%s\" failed",
-								  "SHOW transaction_read_only");
+										"SHOW transaction_read_only");
 
 				/* Close connection politely. */
 				conn->status = CONNECTION_OK;
@@ -3755,7 +3755,7 @@ keep_going:						/* We will come back to here until there is
 
 				/* Append error report to conn->errorMessage. */
 				libpq_append_conn_error(conn, "\"%s\" failed",
-								  "SELECT pg_is_in_recovery()");
+										"SELECT pg_is_in_recovery()");
 
 				/* Close connection politely. */
 				conn->status = CONNECTION_OK;
@@ -3768,8 +3768,8 @@ keep_going:						/* We will come back to here until there is
 
 		default:
 			libpq_append_conn_error(conn,
-							   "invalid connection state %d, probably indicative of memory corruption",
-							  conn->status);
+									"invalid connection state %d, probably indicative of memory corruption",
+									conn->status);
 			goto error_return;
 	}
 
@@ -7148,7 +7148,7 @@ pgpassfileWarning(PGconn *conn)
 
 		if (sqlstate && strcmp(sqlstate, ERRCODE_INVALID_PASSWORD) == 0)
 			libpq_append_conn_error(conn, "password retrieved from file \"%s\"",
-							  conn->pgpassfile);
+									conn->pgpassfile);
 	}
 }
 
diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index ec62550e38..0c2dae6ed9 100644
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -1444,7 +1444,7 @@ PQsendQueryInternal(PGconn *conn, const char *query, bool newQuery)
 	if (conn->pipelineStatus != PQ_PIPELINE_OFF)
 	{
 		libpq_append_conn_error(conn, "%s not allowed in pipeline mode",
-						  "PQsendQuery");
+								"PQsendQuery");
 		return 0;
 	}
 
@@ -1512,7 +1512,7 @@ PQsendQueryParams(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1558,7 +1558,7 @@ PQsendPrepare(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1652,7 +1652,7 @@ PQsendQueryPrepared(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -2099,10 +2099,9 @@ PQgetResult(PGconn *conn)
 
 			/*
 			 * We're about to return the NULL that terminates the round of
-			 * results from the current query; prepare to send the results
-			 * of the next query, if any, when we're called next.  If there's
-			 * no next element in the command queue, this gets us in IDLE
-			 * state.
+			 * results from the current query; prepare to send the results of
+			 * the next query, if any, when we're called next.  If there's no
+			 * next element in the command queue, this gets us in IDLE state.
 			 */
 			pqPipelineProcessQueue(conn);
 			res = NULL;			/* query is complete */
@@ -3047,6 +3046,7 @@ pqPipelineProcessQueue(PGconn *conn)
 			return;
 
 		case PGASYNC_IDLE:
+
 			/*
 			 * If we're in IDLE mode and there's some command in the queue,
 			 * get us into PIPELINE_IDLE mode and process normally.  Otherwise
diff --git a/src/interfaces/libpq/fe-lobj.c b/src/interfaces/libpq/fe-lobj.c
index 4cb6a46859..206266fd04 100644
--- a/src/interfaces/libpq/fe-lobj.c
+++ b/src/interfaces/libpq/fe-lobj.c
@@ -142,7 +142,7 @@ lo_truncate(PGconn *conn, int fd, size_t len)
 	if (conn->lobjfuncs->fn_lo_truncate == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate");
+								"lo_truncate");
 		return -1;
 	}
 
@@ -205,7 +205,7 @@ lo_truncate64(PGconn *conn, int fd, pg_int64 len)
 	if (conn->lobjfuncs->fn_lo_truncate64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate64");
+								"lo_truncate64");
 		return -1;
 	}
 
@@ -395,7 +395,7 @@ lo_lseek64(PGconn *conn, int fd, pg_int64 offset, int whence)
 	if (conn->lobjfuncs->fn_lo_lseek64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek64");
+								"lo_lseek64");
 		return -1;
 	}
 
@@ -485,7 +485,7 @@ lo_create(PGconn *conn, Oid lobjId)
 	if (conn->lobjfuncs->fn_lo_create == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_create");
+								"lo_create");
 		return InvalidOid;
 	}
 
@@ -558,7 +558,7 @@ lo_tell64(PGconn *conn, int fd)
 	if (conn->lobjfuncs->fn_lo_tell64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell64");
+								"lo_tell64");
 		return -1;
 	}
 
@@ -667,7 +667,7 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 	if (fd < 0)
 	{							/* error */
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -723,8 +723,8 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not read from file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -778,8 +778,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -799,8 +799,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 			/* deliberately overwrite any error from lo_close */
 			pqClearConnErrorState(conn);
 			libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-							  filename,
-							  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+									filename,
+									strerror_r(save_errno, sebuf, sizeof(sebuf)));
 			return -1;
 		}
 	}
@@ -822,7 +822,7 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 	if (close(fd) != 0 && result >= 0)
 	{
 		libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		result = -1;
 	}
 
@@ -954,56 +954,56 @@ lo_initialize(PGconn *conn)
 	if (lobjfuncs->fn_lo_open == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_open");
+								"lo_open");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_close == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_close");
+								"lo_close");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_creat == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_creat");
+								"lo_creat");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_unlink == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_unlink");
+								"lo_unlink");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_lseek == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek");
+								"lo_lseek");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_tell == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell");
+								"lo_tell");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_read == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "loread");
+								"loread");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_write == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lowrite");
+								"lowrite");
 		free(lobjfuncs);
 		return -1;
 	}
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 3653a1a8a6..660cdec93c 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -749,8 +749,8 @@ retry4:
 	 */
 definitelyEOF:
 	libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-					   "\tThis probably means the server terminated abnormally\n"
-					   "\tbefore or while processing the request.");
+							"\tThis probably means the server terminated abnormally\n"
+							"\tbefore or while processing the request.");
 
 	/* Come here if lower-level code already set a suitable errorMessage */
 definitelyFailed:
@@ -1067,7 +1067,7 @@ pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s() failed: %s", "select",
-						  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 	}
 
 	return result;
@@ -1280,7 +1280,7 @@ libpq_ngettext(const char *msgid, const char *msgid_plural, unsigned long n)
  * newline.
  */
 void
-libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
+libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
@@ -1309,7 +1309,7 @@ libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
  * format should not end with a newline.
  */
 void
-libpq_append_conn_error(PGconn *conn, const char *fmt, ...)
+libpq_append_conn_error(PGconn *conn, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index 8ab6a88416..b79d74f748 100644
--- a/src/interfaces/libpq/fe-protocol3.c
+++ b/src/interfaces/libpq/fe-protocol3.c
@@ -466,7 +466,7 @@ static void
 handleSyncLoss(PGconn *conn, char id, int msgLength)
 {
 	libpq_append_conn_error(conn, "lost synchronization with server: got message type \"%c\", length %d",
-					  id, msgLength);
+							id, msgLength);
 	/* build an error result holding the error message */
 	pqSaveErrorResult(conn);
 	conn->asyncStatus = PGASYNC_READY;	/* drop out of PQgetResult wait loop */
diff --git a/src/interfaces/libpq/fe-secure-common.c b/src/interfaces/libpq/fe-secure-common.c
index de115b3764..3ecc7bf615 100644
--- a/src/interfaces/libpq/fe-secure-common.c
+++ b/src/interfaces/libpq/fe-secure-common.c
@@ -226,7 +226,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 		 * wrong given the subject matter.
 		 */
 		libpq_append_conn_error(conn, "certificate contains IP address with invalid length %zu",
-						  iplen);
+								iplen);
 		return -1;
 	}
 
@@ -235,7 +235,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 	if (!addrstr)
 	{
 		libpq_append_conn_error(conn, "could not convert certificate's IP address to string: %s",
-						  strerror_r(errno, sebuf, sizeof(sebuf)));
+								strerror_r(errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -292,7 +292,7 @@ pq_verify_peer_name_matches_certificate(PGconn *conn)
 		else if (names_examined == 1)
 		{
 			libpq_append_conn_error(conn, "server certificate for \"%s\" does not match host name \"%s\"",
-							  first_name, host);
+									first_name, host);
 		}
 		else
 		{
diff --git a/src/interfaces/libpq/fe-secure-gssapi.c b/src/interfaces/libpq/fe-secure-gssapi.c
index 6220e4a101..bed6e62435 100644
--- a/src/interfaces/libpq/fe-secure-gssapi.c
+++ b/src/interfaces/libpq/fe-secure-gssapi.c
@@ -213,8 +213,8 @@ pg_GSS_write(PGconn *conn, const void *ptr, size_t len)
 		if (output.length > PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "client tried to send oversize GSSAPI packet (%zu > %zu)",
-							  (size_t) output.length,
-							  PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
+									(size_t) output.length,
+									PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			goto cleanup;
 		}
@@ -349,8 +349,8 @@ pg_GSS_read(PGconn *conn, void *ptr, size_t len)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			return -1;
 		}
@@ -588,8 +588,8 @@ pqsecure_open_gss(PGconn *conn)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			return PGRES_POLLING_FAILED;
 		}
 
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index 983536de25..ab2cbf045b 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -213,12 +213,12 @@ rloop:
 				if (result_errno == EPIPE ||
 					result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -313,12 +313,12 @@ pgtls_write(PGconn *conn, const void *ptr, size_t len)
 				result_errno = SOCK_ERRNO;
 				if (result_errno == EPIPE || result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -410,7 +410,7 @@ pgtls_get_peer_certificate_hash(PGconn *conn, size_t *len)
 			if (algo_type == NULL)
 			{
 				libpq_append_conn_error(conn, "could not find digest for NID %s",
-								  OBJ_nid2sn(algo_nid));
+										OBJ_nid2sn(algo_nid));
 				return NULL;
 			}
 			break;
@@ -962,7 +962,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_min_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for minimum SSL protocol version",
-							  conn->ssl_min_protocol_version);
+									conn->ssl_min_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -988,7 +988,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_max_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for maximum SSL protocol version",
-							  conn->ssl_max_protocol_version);
+									conn->ssl_max_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1032,7 +1032,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read root certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1084,10 +1084,10 @@ initialize_SSL(PGconn *conn)
 			 */
 			if (fnbuf[0] == '\0')
 				libpq_append_conn_error(conn, "could not get home directory to locate root certificate file\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.");
+										"Either provide the file or change sslmode to disable server certificate verification.");
 			else
 				libpq_append_conn_error(conn, "root certificate file \"%s\" does not exist\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
+										"Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1117,7 +1117,7 @@ initialize_SSL(PGconn *conn)
 		if (errno != ENOENT && errno != ENOTDIR)
 		{
 			libpq_append_conn_error(conn, "could not open certificate file \"%s\": %s",
-							  fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
+									fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1135,7 +1135,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1234,7 +1234,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				free(engine_str);
 				return -1;
@@ -1245,7 +1245,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not initialize SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				ENGINE_free(conn->engine);
 				conn->engine = NULL;
@@ -1260,7 +1260,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not read private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1273,7 +1273,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1310,10 +1310,10 @@ initialize_SSL(PGconn *conn)
 		{
 			if (errno == ENOENT)
 				libpq_append_conn_error(conn, "certificate present, but not private key file \"%s\"",
-								  fnbuf);
+										fnbuf);
 			else
 				libpq_append_conn_error(conn, "could not stat private key file \"%s\": %m",
-								  fnbuf);
+										fnbuf);
 			return -1;
 		}
 
@@ -1321,7 +1321,7 @@ initialize_SSL(PGconn *conn)
 		if (!S_ISREG(buf.st_mode))
 		{
 			libpq_append_conn_error(conn, "private key file \"%s\" is not a regular file",
-							  fnbuf);
+									fnbuf);
 			return -1;
 		}
 
@@ -1378,7 +1378,7 @@ initialize_SSL(PGconn *conn)
 			if (SSL_use_PrivateKey_file(conn->ssl, fnbuf, SSL_FILETYPE_ASN1) != 1)
 			{
 				libpq_append_conn_error(conn, "could not load private key file \"%s\": %s",
-								  fnbuf, err);
+										fnbuf, err);
 				SSLerrfree(err);
 				return -1;
 			}
@@ -1394,7 +1394,7 @@ initialize_SSL(PGconn *conn)
 		char	   *err = SSLerrmessage(ERR_get_error());
 
 		libpq_append_conn_error(conn, "certificate does not match private key file \"%s\": %s",
-						  fnbuf, err);
+								fnbuf, err);
 		SSLerrfree(err);
 		return -1;
 	}
@@ -1447,7 +1447,7 @@ open_client_SSL(PGconn *conn)
 
 					if (r == -1)
 						libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-										  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					else
 						libpq_append_conn_error(conn, "SSL SYSCALL error: EOF detected");
 					pgtls_close(conn);
@@ -1489,12 +1489,12 @@ open_client_SSL(PGconn *conn)
 						case SSL_R_VERSION_TOO_LOW:
 #endif
 							libpq_append_conn_error(conn, "This may indicate that the server does not support any SSL protocol version between %s and %s.",
-											  conn->ssl_min_protocol_version ?
-											  conn->ssl_min_protocol_version :
-											  MIN_OPENSSL_TLS_VERSION,
-											  conn->ssl_max_protocol_version ?
-											  conn->ssl_max_protocol_version :
-											  MAX_OPENSSL_TLS_VERSION);
+													conn->ssl_min_protocol_version ?
+													conn->ssl_min_protocol_version :
+													MIN_OPENSSL_TLS_VERSION,
+													conn->ssl_max_protocol_version ?
+													conn->ssl_max_protocol_version :
+													MAX_OPENSSL_TLS_VERSION);
 							break;
 						default:
 							break;
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index 66e401bf3d..8069e38142 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -255,14 +255,14 @@ pqsecure_raw_read(PGconn *conn, void *ptr, size_t len)
 			case EPIPE:
 			case ECONNRESET:
 				libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-								   "\tThis probably means the server terminated abnormally\n"
-								   "\tbefore or while processing the request.");
+										"\tThis probably means the server terminated abnormally\n"
+										"\tbefore or while processing the request.");
 				break;
 
 			default:
 				libpq_append_conn_error(conn, "could not receive data from server: %s",
-								  SOCK_STRERROR(result_errno,
-												sebuf, sizeof(sebuf)));
+										SOCK_STRERROR(result_errno,
+													  sebuf, sizeof(sebuf)));
 				break;
 		}
 	}
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index d94b648ea5..712d572373 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -888,8 +888,8 @@ extern char *libpq_ngettext(const char *msgid, const char *msgid_plural, unsigne
  */
 #undef _
 
-extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...) pg_attribute_printf(2, 3);
-extern void libpq_append_conn_error(PGconn *conn, const char *fmt, ...) pg_attribute_printf(2, 3);
+extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...) pg_attribute_printf(2, 3);
+extern void libpq_append_conn_error(PGconn *conn, const char *fmt,...) pg_attribute_printf(2, 3);
 
 /*
  * These macros are needed to let error-handling code be portable between
-- 
2.34.1

From 83d0abde7db0ddd07f62521c15812f73827f3d61 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <github-tech@jeltef.nl>
Date: Mon, 12 Sep 2022 09:44:06 +0200
Subject: [PATCH v6 2/2] Support load balancing in libpq

This adds support for load balancing to libpq using the newly added
load_balance_hosts parameter. When setting the load_balance_hosts
parameter to random, hosts and addresses will be connected to in a
random order. This then results in load balancing across these
hosts/addresses if multiple clients do this at the same time.

This patch implements two levels of random load balancing:
1. The given hosts are randomly shuffled, before resolving them
    one-by-one.
2. Once a host its addresses get resolved, those addresses are shuffled,
    before trying to connect to them one-by-one.
---
 .cirrus.yml                               |  14 ++
 doc/src/sgml/libpq.sgml                   |  69 +++++++
 src/include/libpq/pqcomm.h                |   6 +
 src/interfaces/libpq/fe-connect.c         | 215 ++++++++++++++++++----
 src/interfaces/libpq/libpq-int.h          |  21 ++-
 src/interfaces/libpq/meson.build          |   1 +
 src/interfaces/libpq/t/003_loadbalance.pl | 167 +++++++++++++++++
 7 files changed, 460 insertions(+), 33 deletions(-)
 create mode 100644 src/interfaces/libpq/t/003_loadbalance.pl

diff --git a/.cirrus.yml b/.cirrus.yml
index 69837bcd5a..f71e93451f 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -308,6 +308,14 @@ task:
     mkdir -m 770 /tmp/cores
     chown root:postgres /tmp/cores
     sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core'
+
+  setup_hosts_file_script: |
+    cat >> /etc/hosts <<-EOF
+      127.0.0.1 pg-loadbalancetest
+      127.0.0.2 pg-loadbalancetest
+      127.0.0.3 pg-loadbalancetest
+    EOF
+
   setup_additional_packages_script: |
     #apt-get update
     #DEBIAN_FRONTEND=noninteractive apt-get -y install ...
@@ -557,6 +565,12 @@ task:
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
+  setup_hosts_file_script: |
+    echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    type c:\Windows\System32\Drivers\etc\hosts
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index af278660eb..03eab1d02e 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1964,6 +1964,75 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="libpq-connect-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls the order in which the client tries to connect to the available
+        hosts and addresses. It's typically used in combination with multiple
+        host names or a DNS record that returns multiple IPs. This parameter be
+        used in combination with <xref linkend="libpq-connect-target-session-attrs"/>
+        to, for example, load balance over stanby servers only. Once successfully
+        connected, subsequent queries on the returned connection will all be
+        sent to the same server. There are currently two modes:
+        <variablelist>
+         <varlistentry>
+          <term><literal>disable</literal> (default)</term>
+          <listitem>
+           <para>
+            Hosts are tried in the order in which they are provided and
+            addresses are tried in the order they are received from DNS or a
+            hosts file.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>random</literal></term>
+          <listitem>
+           <para>
+            The provided hosts and the addresses that they resolve to are
+            tried in random order. This value is mostly useful when opening
+            multiple connections at the same time, possibly from different
+            machines. This way connections can be load balanced across multiple
+            Postgres servers.
+           </para>
+           <para>
+            This algorithm uses two levels of random choices: First the hosts
+            will be resolved in random order. Then before resolving the next
+            host, all resolved addresses for the current host will be tried in
+            random order. This behaviour can lead to non-uniform address
+            selection in certain cases, for instance when some hosts resolve to
+            more addresses than others. So if you want uniform load balancing,
+            this is something to keep in mind. However, non-uniform load
+            balancing also can be used to your advantage, e.g. by providing the
+            hostname of a larger server multiple times in the host string so it
+            gets more connections.
+           </para>
+           <para>
+            When using this value it's recommended to also configure a reasonable
+            value for <xref linkend="libpq-connect-connect-timeout"/>. Because then,
+            if one of the nodes that are used for load balancing is not responding,
+            a new node will be tried.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-random-seed" xreflabel="random_seed">
+      <term><literal>random_seed</literal></term>
+      <listitem>
+       <para>
+        Sets the random seed that is used by <xref linkend="libpq-connect-load-balance-hosts"/>
+        to randomize the host order. This option is mostly useful when running
+        tests that require a stable random order.
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
    </para>
   </sect2>
diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index 66ba359390..ee28e223bd 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+} AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 773e9e1f3a..18a07d810d 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -123,6 +123,7 @@ static int	ldapServiceLookup(const char *purl, PQconninfoOption *options,
 #define DefaultChannelBinding	"disable"
 #endif
 #define DefaultTargetSessionAttrs	"any"
+#define DefaultLoadBalanceHosts	"disable"
 #ifdef USE_SSL
 #define DefaultSSLMode "prefer"
 #else
@@ -341,6 +342,15 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Target-Session-Attrs", "", 15, /* sizeof("prefer-standby") = 15 */
 	offsetof(struct pg_conn, target_session_attrs)},
 
+	{"load_balance_hosts", "PGLOADBALANCEHOSTS",
+		DefaultLoadBalanceHosts, NULL,
+		"Load-Balance-Hosts", "", 8,	/* sizeof("disable") = 8 */
+	offsetof(struct pg_conn, load_balance_hosts)},
+
+	{"random_seed", NULL, NULL, NULL,
+		"Random-Seed", "", 10,	/* strlen(INT32_MAX) == 10 */
+	offsetof(struct pg_conn, randomseed)},
+
 	/* Terminating entry --- MUST BE LAST */
 	{NULL, NULL, NULL, NULL,
 	NULL, NULL, 0}
@@ -379,6 +389,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *connstr,
@@ -424,6 +435,8 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static bool parse_int_param(const char *value, int *result, PGconn *conn,
+							const char *context);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1007,6 +1020,44 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on timestamp and PID.
+ */
+static bool
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(conn->randomseed))
+	{
+		int			rseed;
+
+		if (!parse_int_param(conn->randomseed, &rseed, conn, "random_seed"))
+			return false;
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	else if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		time_t		now = time(NULL);
+
+		/*
+		 * Since PIDs and timestamps tend to change more frequently in their
+		 * least significant bits, shift the timestamp left to allow a larger
+		 * total number of seeds in a given time period.  Since that would
+		 * leave only 20 bits of the timestamp that cycle every ~1 second,
+		 * also mix in some higher bits.
+		 */
+		rseed = ((uint64) getpid()) ^
+			((uint64) now << 12) ^
+			((uint64) now >> 20);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	return true;
+}
+
 /*
  *		connectOptions2
  *
@@ -1400,6 +1451,47 @@ connectOptions2(PGconn *conn)
 	else
 		conn->target_server_type = SERVER_TYPE_ANY;
 
+	/*
+	 * validate load_balance_hosts option, and set load_balance_type
+	 */
+	if (conn->load_balance_hosts)
+	{
+		if (strcmp(conn->load_balance_hosts, "disable") == 0)
+			conn->load_balance_type = LOAD_BALANCE_DISABLE;
+		else if (strcmp(conn->load_balance_hosts, "random") == 0)
+			conn->load_balance_type = LOAD_BALANCE_RANDOM;
+		else
+		{
+			conn->status = CONNECTION_BAD;
+			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
+									"load_balance_hosts",
+									conn->load_balance_hosts);
+			return false;
+		}
+	}
+	else
+		conn->load_balance_type = LOAD_BALANCE_DISABLE;
+
+	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+	{
+		if (!libpq_prng_init(conn))
+			return false;
+
+		/*
+		 * Shuffle connhost with a Durstenfeld/Knuth version of the
+		 * Fisher-Yates shuffle. Source:
+		 * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
+		 */
+		for (i = conn->nconnhost - 1; i > 0; i--)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
 	/*
 	 * Resolve special "auto" client_encoding from the locale
 	 */
@@ -2077,7 +2169,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2121,11 +2213,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2272,9 +2364,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2287,6 +2379,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2327,7 +2420,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2350,8 +2443,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
 											ch->host, gai_strerror(ret));
@@ -2362,8 +2455,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
 											ch->hostaddr, gai_strerror(ret));
@@ -2372,7 +2465,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2387,8 +2480,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
 											portstr, gai_strerror(ret));
@@ -2397,8 +2490,14 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		if (!store_conn_addrinfo(conn, addrlist))
+		{
+			pg_freeaddrinfo_all(hint.ai_family, addrlist);
+			libpq_append_conn_error(conn, "out of memory");
+			goto error_return;
+		}
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2455,30 +2554,29 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2494,7 +2592,7 @@ keep_going:						/* We will come back to here until there is
 						conn->connip = strdup(host_addr);
 
 					/* Try to create the socket */
-					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
+					conn->sock = socket(addr_cur->family, SOCK_STREAM, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2505,7 +2603,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2531,7 +2629,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2558,7 +2656,7 @@ keep_going:						/* We will come back to here until there is
 					}
 #endif							/* F_SETFD */
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2650,8 +2748,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4035,12 +4133,68 @@ freePGconn(PGconn *conn)
 	free(conn->outBuffer);
 	free(conn->rowBuf);
 	free(conn->target_session_attrs);
+	free(conn->load_balance_hosts);
+	free(conn->randomseed);
 	termPQExpBuffer(&conn->errorMessage);
 	termPQExpBuffer(&conn->workBuffer);
 
 	free(conn);
 }
 
+/*
+ * Copies over the AddrInfos from addrlist to the PGconn.
+ */
+static bool
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+		return false;
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+	{
+		/*
+		 * Shuffle addr with a Durstenfeld/Knuth version of the Fisher-Yates
+		 * shuffle. Source:
+		 * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
+		 *
+		 * We don't need to initialize conn->prng_state here, because that
+		 * already happened in connectOptions2.
+		 */
+		for (int i = conn->naddr - 1; i > 0; i--)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			AddrInfo	temp = conn->addr[j];
+
+			conn->addr[j] = conn->addr[i];
+			conn->addr[i] = temp;
+		}
+	}
+	return true;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4048,11 +4202,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 712d572373..86dd1d6d40 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -82,6 +82,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -242,6 +244,13 @@ typedef enum
 	SERVER_TYPE_PREFER_STANDBY_PASS2	/* second pass - behaves same as ANY */
 } PGTargetServerType;
 
+/* Target server type (decoded value of load_balance_hosts) */
+typedef enum
+{
+	LOAD_BALANCE_DISABLE = 0,	/* Use the existing host order (default) */
+	LOAD_BALANCE_RANDOM,		/* Read-write server */
+}			PGLoadBalanceType;
+
 /* Boolean value plus a not-known state, for GUCs we might have to fetch */
 typedef enum
 {
@@ -396,6 +405,8 @@ struct pg_conn
 	char	   *ssl_min_protocol_version;	/* minimum TLS protocol version */
 	char	   *ssl_max_protocol_version;	/* maximum TLS protocol version */
 	char	   *target_session_attrs;	/* desired session properties */
+	char	   *load_balance_hosts; /* load balance over hosts */
+	char	   *randomseed;		/* seed for randomization of load balancing */
 
 	/* Optional file to write trace info to */
 	FILE	   *Pfdebug;
@@ -459,10 +470,14 @@ struct pg_conn
 
 	/* Transient state needed while establishing connection */
 	PGTargetServerType target_server_type;	/* desired session properties */
+	PGLoadBalanceType load_balance_type;	/* desired load balancing
+											 * algorithm */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
+	int			naddr;			/* number of addresses returned by getaddrinfo */
+	int			whichaddr;		/* the address currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	int			addrlist_family;	/* needed to know how to free addrlist */
 	bool		send_appname;	/* okay to send application_name? */
 
@@ -477,6 +492,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index 573fd9b6ea..52b327500c 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -116,6 +116,7 @@ tests += {
     'tests': [
       't/001_uri.pl',
       't/002_api.pl',
+      't/003_loadbalance.pl',
     ],
     'env': {'with_ssl': get_option('ssl')},
   },
diff --git a/src/interfaces/libpq/t/003_loadbalance.pl b/src/interfaces/libpq/t/003_loadbalance.pl
new file mode 100644
index 0000000000..1b4e8fd813
--- /dev/null
+++ b/src/interfaces/libpq/t/003_loadbalance.pl
@@ -0,0 +1,167 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use File::Spec::Functions 'catfile';
+use Test::More;
+
+# This tests two different methods of load balancing from libpq
+# 1. Load balancing by providing multiple host and port combinations in the
+#    libpq connection string.
+# 2. By using a hosts file where hostname maps to multiple different IP
+#    addresses. Regular Postgres users wouldn't usually use such a host file,
+#    but this is the easiest way to immitate behaviour of a DNS server that
+#    returns multiple IP addresses for the same DNS record.
+#
+# Testing method 1 is supported on all platforms and works out of the box. But
+# testing method 2 has some more requirements, both on the platform and on the
+# initial setup. If any of these requirements are not met, then method 2 is
+# simply not tested.
+#
+# The requirements to test method 2 are as follows:
+# 1. Windows or Linux should be used.
+# 2. The OS hosts file at /etc/hosts or c:\Windows\System32\Drivers\etc\hosts
+#    should contain the following contents:
+#
+# 127.0.0.1 pg-loadbalancetest
+# 127.0.0.2 pg-loadbalancetest
+# 127.0.0.3 pg-loadbalancetest
+#
+#
+# Windows or Linux are required to test method 2 because these OSes allow
+# binding to 127.0.0.2 and 127.0.0.3 addresess by default, but other OSes
+# don't. We need to bind to different IP addresses, so that we can use these
+# different IP addresses in the hosts file.
+#
+# The hosts file needs to be prepared before running this test. We don't do it
+# on the fly, because it requires root permissions to change the hosts file. In
+# CI we set up the previously mentioned rules in the hosts file, so that this
+# load balancing method is tested.
+
+
+# Cluster setup which is shared for testing both load balancing methods
+my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os;
+
+if ($can_bind_to_127_0_0_2)
+{
+	$PostgreSQL::Test::Cluster::use_tcp = 1;
+	$PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1';
+}
+my $port = PostgreSQL::Test::Cluster::get_free_port();
+my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port);
+my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# Start the tests for load balancing method 1
+my $hostlist = $node1->host . ',' . $node2->host . ',' . $node3->host;
+my $portlist = "$port,$port,$port";
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=123",
+	"seed 123 selects node 1 first",
+	sql => "SELECT 'connect1'",
+	log_like => [qr/statement: SELECT 'connect1'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=123",
+	"seed 123 does not select node 2 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=123",
+	"seed 123 does not select node 3 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 selects node 3 first",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 1 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node3->stop();
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does select node 1 second",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 second",
+	sql => "SELECT 'connect3'",
+	log_unlike => [qr/statement: SELECT 'connect3'/]);
+
+$node3->start();
+
+# Checks for the requirements for testing load balancing method 2
+if (!$can_bind_to_127_0_0_2) {
+	# The OS requirement is not met
+	done_testing();
+	exit;
+}
+
+my $hosts_path;
+if ($windows_os) {
+	$hosts_path = 'c:\Windows\System32\Drivers\etc\hosts';
+}
+else
+{
+	$hosts_path = '/etc/hosts';
+}
+
+my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path);
+
+if ($hosts_content !~ m/pg-loadbalancetest/) {
+	# Host file is not prepared for this test
+	done_testing();
+	exit;
+}
+
+# Start the tests for load balancing method 2
+$node2->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=44",
+	"seed 44 selects node 2 first",
+	sql => "SELECT 'connect4'",
+	log_like => [qr/statement: SELECT 'connect4'/]);
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=44",
+	"seed 44 does not select node 1 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=44",
+	"seed 44 does not select node 3 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node2->stop();
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=44",
+	"seed 44 does select node 1 second",
+	sql => "SELECT 'connect5'",
+	log_like => [qr/statement: SELECT 'connect5'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=44",
+	"seed 44 does not select node 3 second",
+	sql => "SELECT 'connect5'",
+	log_unlike => [qr/statement: SELECT 'connect5'/]);
+
+done_testing();
-- 
2.34.1

From 561dca3b9510464600b4da8d1397e7762f523568 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Fri, 13 Jan 2023 16:52:17 +0100
Subject: [PATCH v7 3/4] Make mutexes easier to use in libpq

For process global mutexes windows requires some different setup than
other OSes. This abstracts away that logic into the newly added pglock
and pgunlock functions. The main reason to do this refactoring is to
prepare for a new global mutex that will be added in a follow up commit.
---
 src/interfaces/libpq/fe-connect.c        | 58 +++++++++++++++---------
 src/interfaces/libpq/fe-secure-openssl.c | 33 +++-----------
 src/interfaces/libpq/libpq-int.h         | 21 +++++++++
 3 files changed, 64 insertions(+), 48 deletions(-)

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 18a07d810dc..69ed891703a 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -7424,36 +7424,17 @@ pqGetHomeDirectory(char *buf, int bufsize)
 static void
 default_threadlock(int acquire)
 {
-#ifdef ENABLE_THREAD_SAFETY
-#ifndef WIN32
-	static pthread_mutex_t singlethread_lock = PTHREAD_MUTEX_INITIALIZER;
-#else
-	static pthread_mutex_t singlethread_lock = NULL;
-	static long mutex_initlock = 0;
-
-	if (singlethread_lock == NULL)
-	{
-		while (InterlockedExchange(&mutex_initlock, 1) == 1)
-			 /* loop, another thread own the lock */ ;
-		if (singlethread_lock == NULL)
-		{
-			if (pthread_mutex_init(&singlethread_lock, NULL))
-				Assert(false);
-		}
-		InterlockedExchange(&mutex_initlock, 0);
-	}
-#endif
+	static pglock_t singlethread_lock = PGLOCK_INITIALIZER;
 	if (acquire)
 	{
-		if (pthread_mutex_lock(&singlethread_lock))
+		if (!pglock(&singlethread_lock))
 			Assert(false);
 	}
 	else
 	{
-		if (pthread_mutex_unlock(&singlethread_lock))
+		if (!pgunlock(&singlethread_lock))
 			Assert(false);
 	}
-#endif
 }
 
 pgthreadlock_t
@@ -7468,3 +7449,36 @@ PQregisterThreadLock(pgthreadlock_t newhandler)
 
 	return prev;
 }
+
+bool
+pglock(pglock_t * lock)
+{
+#ifdef WIN32
+	if (lock->mutex == NULL)
+	{
+		while (InterlockedExchange(&lock->mutex_initlock, 1) == 1)
+			 /* loop, another thread own the lock */ ;
+		if (lock->mutex == NULL)
+		{
+			if (pthread_mutex_init(&lock->mutex, NULL))
+				return false;
+		}
+		InterlockedExchange(&lock->mutex_initlock, 0);
+	}
+#endif
+	if (pthread_mutex_lock(&lock->mutex))
+	{
+		return false;
+	}
+	return true;
+}
+
+bool
+pgunlock(pglock_t * lock)
+{
+	if (pthread_mutex_unlock(&lock->mutex))
+	{
+		return false;
+	}
+	return true;
+}
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index ab2cbf045b8..c52c2ccf217 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -94,12 +94,7 @@ static bool ssl_lib_initialized = false;
 #ifdef ENABLE_THREAD_SAFETY
 static long crypto_open_connections = 0;
 
-#ifndef WIN32
-static pthread_mutex_t ssl_config_mutex = PTHREAD_MUTEX_INITIALIZER;
-#else
-static pthread_mutex_t ssl_config_mutex = NULL;
-static long win32_ssl_create_mutex = 0;
-#endif
+static pglock_t ssl_config_lock = PGLOCK_INITIALIZER;
 #endif							/* ENABLE_THREAD_SAFETY */
 
 static PQsslKeyPassHook_OpenSSL_type PQsslKeyPassHook = NULL;
@@ -744,21 +739,7 @@ int
 pgtls_init(PGconn *conn, bool do_ssl, bool do_crypto)
 {
 #ifdef ENABLE_THREAD_SAFETY
-#ifdef WIN32
-	/* Also see similar code in fe-connect.c, default_threadlock() */
-	if (ssl_config_mutex == NULL)
-	{
-		while (InterlockedExchange(&win32_ssl_create_mutex, 1) == 1)
-			 /* loop, another thread own the lock */ ;
-		if (ssl_config_mutex == NULL)
-		{
-			if (pthread_mutex_init(&ssl_config_mutex, NULL))
-				return -1;
-		}
-		InterlockedExchange(&win32_ssl_create_mutex, 0);
-	}
-#endif
-	if (pthread_mutex_lock(&ssl_config_mutex))
+	if (!pglock(&ssl_config_lock))
 		return -1;
 
 #ifdef HAVE_CRYPTO_LOCK
@@ -775,7 +756,7 @@ pgtls_init(PGconn *conn, bool do_ssl, bool do_crypto)
 			pq_lockarray = malloc(sizeof(pthread_mutex_t) * CRYPTO_num_locks());
 			if (!pq_lockarray)
 			{
-				pthread_mutex_unlock(&ssl_config_mutex);
+				pgunlock(&ssl_config_lock);
 				return -1;
 			}
 			for (i = 0; i < CRYPTO_num_locks(); i++)
@@ -784,7 +765,7 @@ pgtls_init(PGconn *conn, bool do_ssl, bool do_crypto)
 				{
 					free(pq_lockarray);
 					pq_lockarray = NULL;
-					pthread_mutex_unlock(&ssl_config_mutex);
+					pgunlock(&ssl_config_lock);
 					return -1;
 				}
 			}
@@ -827,7 +808,7 @@ pgtls_init(PGconn *conn, bool do_ssl, bool do_crypto)
 	}
 
 #ifdef ENABLE_THREAD_SAFETY
-	pthread_mutex_unlock(&ssl_config_mutex);
+	pgunlock(&ssl_config_lock);
 #endif
 	return 0;
 }
@@ -849,7 +830,7 @@ destroy_ssl_system(void)
 {
 #if defined(ENABLE_THREAD_SAFETY) && defined(HAVE_CRYPTO_LOCK)
 	/* Mutex is created in pgtls_init() */
-	if (pthread_mutex_lock(&ssl_config_mutex))
+	if (!pglock(&ssl_config_lock))
 		return;
 
 	if (pq_init_crypto_lib && crypto_open_connections > 0)
@@ -875,7 +856,7 @@ destroy_ssl_system(void)
 		 */
 	}
 
-	pthread_mutex_unlock(&ssl_config_mutex);
+	pgunlock(&ssl_config_lock);
 #endif
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 86dd1d6d405..01dd4190f33 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -672,7 +672,28 @@ extern pgthreadlock_t pg_g_threadlock;
 
 #define pglock_thread()		pg_g_threadlock(true)
 #define pgunlock_thread()	pg_g_threadlock(false)
+
+typedef struct pglock_t
+{
+	pthread_mutex_t mutex;
+#ifdef WIN32
+	long		mutex_initlock;
+#endif
+}			pglock_t;
+
+#ifdef WIN32
+#define PGLOCK_INITIALIZER { NULL, 0 }
+#else
+#define PGLOCK_INITIALIZER { PTHREAD_MUTEX_INITIALIZER }
+#endif
+
+extern bool pglock(pglock_t * lock);
+extern bool pgunlock(pglock_t * lock);
 #else
+#define pglock_t bool;
+#define PGLOCK_INITIALIZER false;
+#define pglock(lock)	((void) true)
+#define pgunlock(lock)	((void) true)
 #define pglock_thread()		((void) 0)
 #define pgunlock_thread()	((void) 0)
 #endif
-- 
2.34.1

From c10deacdab931ed30f9c35594e8c99f787989387 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 30 Nov 2022 10:07:19 +0100
Subject: [PATCH v7 1/4] libpq: Run pgindent after a9e9a9f32b3

It seems that pgindent was not run after the error handling refactor in
commit a9e9a9f32b35edf129c88e8b929ef223f8511f59. This fixes that and
also addresses a few other things pgindent wanted to change in libpq.
---
 src/interfaces/libpq/fe-auth-scram.c     |   2 +-
 src/interfaces/libpq/fe-auth.c           |   8 +-
 src/interfaces/libpq/fe-connect.c        | 124 +++++++++++------------
 src/interfaces/libpq/fe-exec.c           |  16 +--
 src/interfaces/libpq/fe-lobj.c           |  42 ++++----
 src/interfaces/libpq/fe-misc.c           |  10 +-
 src/interfaces/libpq/fe-protocol3.c      |   2 +-
 src/interfaces/libpq/fe-secure-common.c  |   6 +-
 src/interfaces/libpq/fe-secure-gssapi.c  |  12 +--
 src/interfaces/libpq/fe-secure-openssl.c |  64 ++++++------
 src/interfaces/libpq/fe-secure.c         |   8 +-
 src/interfaces/libpq/libpq-int.h         |   4 +-
 12 files changed, 149 insertions(+), 149 deletions(-)

diff --git a/src/interfaces/libpq/fe-auth-scram.c b/src/interfaces/libpq/fe-auth-scram.c
index 9c42ea4f819..12c3d0bc333 100644
--- a/src/interfaces/libpq/fe-auth-scram.c
+++ b/src/interfaces/libpq/fe-auth-scram.c
@@ -716,7 +716,7 @@ read_server_final_message(fe_scram_state *state, char *input)
 			return false;
 		}
 		libpq_append_conn_error(conn, "error received from server in SCRAM exchange: %s",
-						   errmsg);
+								errmsg);
 		return false;
 	}
 
diff --git a/src/interfaces/libpq/fe-auth.c b/src/interfaces/libpq/fe-auth.c
index 9afc6f19b9a..ab454e6cd02 100644
--- a/src/interfaces/libpq/fe-auth.c
+++ b/src/interfaces/libpq/fe-auth.c
@@ -73,7 +73,7 @@ pg_GSS_continue(PGconn *conn, int payloadlen)
 		if (!ginbuf.value)
 		{
 			libpq_append_conn_error(conn, "out of memory allocating GSSAPI buffer (%d)",
-							  payloadlen);
+									payloadlen);
 			return STATUS_ERROR;
 		}
 		if (pqGetnchar(ginbuf.value, payloadlen, conn))
@@ -223,7 +223,7 @@ pg_SSPI_continue(PGconn *conn, int payloadlen)
 		if (!inputbuf)
 		{
 			libpq_append_conn_error(conn, "out of memory allocating SSPI buffer (%d)",
-							  payloadlen);
+									payloadlen);
 			return STATUS_ERROR;
 		}
 		if (pqGetnchar(inputbuf, payloadlen, conn))
@@ -623,7 +623,7 @@ pg_SASL_continue(PGconn *conn, int payloadlen, bool final)
 	if (!challenge)
 	{
 		libpq_append_conn_error(conn, "out of memory allocating SASL buffer (%d)",
-						  payloadlen);
+								payloadlen);
 		return STATUS_ERROR;
 	}
 
@@ -1277,7 +1277,7 @@ PQencryptPasswordConn(PGconn *conn, const char *passwd, const char *user,
 	else
 	{
 		libpq_append_conn_error(conn, "unrecognized password encryption algorithm \"%s\"",
-						  algorithm);
+								algorithm);
 		return NULL;
 	}
 
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 50b5df3490b..773e9e1f3a2 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -1079,7 +1079,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "could not match %d host names to %d hostaddr values",
-							   count_comma_separated_elems(conn->pghost), conn->nconnhost);
+									count_comma_separated_elems(conn->pghost), conn->nconnhost);
 			return false;
 		}
 	}
@@ -1159,7 +1159,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "could not match %d port numbers to %d hosts",
-							   count_comma_separated_elems(conn->pgport), conn->nconnhost);
+									count_comma_separated_elems(conn->pgport), conn->nconnhost);
 			return false;
 		}
 	}
@@ -1248,7 +1248,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "channel_binding", conn->channel_binding);
+									"channel_binding", conn->channel_binding);
 			return false;
 		}
 	}
@@ -1273,7 +1273,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "sslmode", conn->sslmode);
+									"sslmode", conn->sslmode);
 			return false;
 		}
 
@@ -1293,7 +1293,7 @@ connectOptions2(PGconn *conn)
 			case 'v':			/* "verify-ca" or "verify-full" */
 				conn->status = CONNECTION_BAD;
 				libpq_append_conn_error(conn, "sslmode value \"%s\" invalid when SSL support is not compiled in",
-								   conn->sslmode);
+										conn->sslmode);
 				return false;
 		}
 #endif
@@ -1313,16 +1313,16 @@ connectOptions2(PGconn *conn)
 	{
 		conn->status = CONNECTION_BAD;
 		libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-						   "ssl_min_protocol_version",
-						   conn->ssl_min_protocol_version);
+								"ssl_min_protocol_version",
+								conn->ssl_min_protocol_version);
 		return false;
 	}
 	if (!sslVerifyProtocolVersion(conn->ssl_max_protocol_version))
 	{
 		conn->status = CONNECTION_BAD;
 		libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-						   "ssl_max_protocol_version",
-						   conn->ssl_max_protocol_version);
+								"ssl_max_protocol_version",
+								conn->ssl_max_protocol_version);
 		return false;
 	}
 
@@ -1359,7 +1359,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "gssencmode value \"%s\" invalid when GSSAPI support is not compiled in",
-							   conn->gssencmode);
+									conn->gssencmode);
 			return false;
 		}
 #endif
@@ -1392,8 +1392,8 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "target_session_attrs",
-							   conn->target_session_attrs);
+									"target_session_attrs",
+									conn->target_session_attrs);
 			return false;
 		}
 	}
@@ -1609,7 +1609,7 @@ connectNoDelay(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "could not set socket to TCP no delay mode: %s",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1787,7 +1787,7 @@ parse_int_param(const char *value, int *result, PGconn *conn,
 
 error:
 	libpq_append_conn_error(conn, "invalid integer value \"%s\" for connection option \"%s\"",
-					   value, context);
+							value, context);
 	return false;
 }
 
@@ -1816,9 +1816,9 @@ setKeepalivesIdle(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   PG_TCP_KEEPALIVE_IDLE_STR,
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								PG_TCP_KEEPALIVE_IDLE_STR,
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1850,9 +1850,9 @@ setKeepalivesInterval(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_KEEPINTVL",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_KEEPINTVL",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1885,9 +1885,9 @@ setKeepalivesCount(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_KEEPCNT",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_KEEPCNT",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1949,8 +1949,8 @@ prepKeepalivesWin32(PGconn *conn)
 	if (!setKeepalivesWin32(conn->sock, idle, interval))
 	{
 		libpq_append_conn_error(conn, "%s(%s) failed: error code %d",
-						  "WSAIoctl", "SIO_KEEPALIVE_VALS",
-						  WSAGetLastError());
+								"WSAIoctl", "SIO_KEEPALIVE_VALS",
+								WSAGetLastError());
 		return 0;
 	}
 	return 1;
@@ -1983,9 +1983,9 @@ setTCPUserTimeout(PGconn *conn)
 		char		sebuf[256];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_USER_TIMEOUT",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_USER_TIMEOUT",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -2354,7 +2354,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
-									   ch->host, gai_strerror(ret));
+											ch->host, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2366,7 +2366,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
-									   ch->hostaddr, gai_strerror(ret));
+											ch->hostaddr, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2377,8 +2377,8 @@ keep_going:						/* We will come back to here until there is
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
 					libpq_append_conn_error(conn, "Unix-domain socket path \"%s\" is too long (maximum %d bytes)",
-									   portstr,
-									   (int) (UNIXSOCK_PATH_BUFLEN - 1));
+											portstr,
+											(int) (UNIXSOCK_PATH_BUFLEN - 1));
 					goto keep_going;
 				}
 
@@ -2391,7 +2391,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
-									   portstr, gai_strerror(ret));
+											portstr, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2513,7 +2513,7 @@ keep_going:						/* We will come back to here until there is
 						}
 						emitHostIdentityInfo(conn, host_addr);
 						libpq_append_conn_error(conn, "could not create socket: %s",
-										   SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2543,7 +2543,7 @@ keep_going:						/* We will come back to here until there is
 					if (!pg_set_noblock(conn->sock))
 					{
 						libpq_append_conn_error(conn, "could not set socket to nonblocking mode: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						conn->try_next_addr = true;
 						goto keep_going;
 					}
@@ -2552,7 +2552,7 @@ keep_going:						/* We will come back to here until there is
 					if (fcntl(conn->sock, F_SETFD, FD_CLOEXEC) == -1)
 					{
 						libpq_append_conn_error(conn, "could not set socket to close-on-exec mode: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						conn->try_next_addr = true;
 						goto keep_going;
 					}
@@ -2581,9 +2581,9 @@ keep_going:						/* We will come back to here until there is
 											(char *) &on, sizeof(on)) < 0)
 						{
 							libpq_append_conn_error(conn, "%s(%s) failed: %s",
-											   "setsockopt",
-											   "SO_KEEPALIVE",
-											   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+													"setsockopt",
+													"SO_KEEPALIVE",
+													SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 							err = 1;
 						}
 						else if (!setKeepalivesIdle(conn)
@@ -2708,7 +2708,7 @@ keep_going:						/* We will come back to here until there is
 							   (char *) &optval, &optlen) == -1)
 				{
 					libpq_append_conn_error(conn, "could not get socket error status: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					goto error_return;
 				}
 				else if (optval != 0)
@@ -2735,7 +2735,7 @@ keep_going:						/* We will come back to here until there is
 								&conn->laddr.salen) < 0)
 				{
 					libpq_append_conn_error(conn, "could not get client address from socket: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					goto error_return;
 				}
 
@@ -2775,7 +2775,7 @@ keep_going:						/* We will come back to here until there is
 							libpq_append_conn_error(conn, "requirepeer parameter is not supported on this platform");
 						else
 							libpq_append_conn_error(conn, "could not get peer credentials: %s",
-											   strerror_r(errno, sebuf, sizeof(sebuf)));
+													strerror_r(errno, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2788,7 +2788,7 @@ keep_going:						/* We will come back to here until there is
 					if (strcmp(remote_username, conn->requirepeer) != 0)
 					{
 						libpq_append_conn_error(conn, "requirepeer specifies \"%s\", but actual peer user name is \"%s\"",
-										   conn->requirepeer, remote_username);
+												conn->requirepeer, remote_username);
 						free(remote_username);
 						goto error_return;
 					}
@@ -2829,7 +2829,7 @@ keep_going:						/* We will come back to here until there is
 					if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
 					{
 						libpq_append_conn_error(conn, "could not send GSSAPI negotiation packet: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2840,7 +2840,7 @@ keep_going:						/* We will come back to here until there is
 				else if (!conn->gctx && conn->gssencmode[0] == 'r')
 				{
 					libpq_append_conn_error(conn,
-									   "GSSAPI encryption required but was impossible (possibly no credential cache, no server support, or using a local socket)");
+											"GSSAPI encryption required but was impossible (possibly no credential cache, no server support, or using a local socket)");
 					goto error_return;
 				}
 #endif
@@ -2882,7 +2882,7 @@ keep_going:						/* We will come back to here until there is
 					if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
 					{
 						libpq_append_conn_error(conn, "could not send SSL negotiation packet: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 					/* Ok, wait for response */
@@ -2911,7 +2911,7 @@ keep_going:						/* We will come back to here until there is
 				if (pqPacketSend(conn, 0, startpacket, packetlen) != STATUS_OK)
 				{
 					libpq_append_conn_error(conn, "could not send startup packet: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					free(startpacket);
 					goto error_return;
 				}
@@ -3012,7 +3012,7 @@ keep_going:						/* We will come back to here until there is
 					else
 					{
 						libpq_append_conn_error(conn, "received invalid response to SSL negotiation: %c",
-										   SSLok);
+												SSLok);
 						goto error_return;
 					}
 				}
@@ -3123,7 +3123,7 @@ keep_going:						/* We will come back to here until there is
 					else if (gss_ok != 'G')
 					{
 						libpq_append_conn_error(conn, "received invalid response to GSSAPI negotiation: %c",
-										   gss_ok);
+												gss_ok);
 						goto error_return;
 					}
 				}
@@ -3201,7 +3201,7 @@ keep_going:						/* We will come back to here until there is
 				if (!(beresp == 'R' || beresp == 'v' || beresp == 'E'))
 				{
 					libpq_append_conn_error(conn, "expected authentication request from server, but received %c",
-									   beresp);
+											beresp);
 					goto error_return;
 				}
 
@@ -3216,17 +3216,17 @@ keep_going:						/* We will come back to here until there is
 				 * Try to validate message length before using it.
 				 * Authentication requests can't be very large, although GSS
 				 * auth requests may not be that small.  Same for
-				 * NegotiateProtocolVersion.  Errors can be a
-				 * little larger, but not huge.  If we see a large apparent
-				 * length in an error, it means we're really talking to a
-				 * pre-3.0-protocol server; cope.  (Before version 14, the
-				 * server also used the old protocol for errors that happened
-				 * before processing the startup packet.)
+				 * NegotiateProtocolVersion.  Errors can be a little larger,
+				 * but not huge.  If we see a large apparent length in an
+				 * error, it means we're really talking to a pre-3.0-protocol
+				 * server; cope.  (Before version 14, the server also used the
+				 * old protocol for errors that happened before processing the
+				 * startup packet.)
 				 */
 				if ((beresp == 'R' || beresp == 'v') && (msgLength < 8 || msgLength > 2000))
 				{
 					libpq_append_conn_error(conn, "expected authentication request from server, but received %c",
-									   beresp);
+											beresp);
 					goto error_return;
 				}
 
@@ -3705,7 +3705,7 @@ keep_going:						/* We will come back to here until there is
 
 				/* Append error report to conn->errorMessage. */
 				libpq_append_conn_error(conn, "\"%s\" failed",
-								  "SHOW transaction_read_only");
+										"SHOW transaction_read_only");
 
 				/* Close connection politely. */
 				conn->status = CONNECTION_OK;
@@ -3755,7 +3755,7 @@ keep_going:						/* We will come back to here until there is
 
 				/* Append error report to conn->errorMessage. */
 				libpq_append_conn_error(conn, "\"%s\" failed",
-								  "SELECT pg_is_in_recovery()");
+										"SELECT pg_is_in_recovery()");
 
 				/* Close connection politely. */
 				conn->status = CONNECTION_OK;
@@ -3768,8 +3768,8 @@ keep_going:						/* We will come back to here until there is
 
 		default:
 			libpq_append_conn_error(conn,
-							   "invalid connection state %d, probably indicative of memory corruption",
-							  conn->status);
+									"invalid connection state %d, probably indicative of memory corruption",
+									conn->status);
 			goto error_return;
 	}
 
@@ -7148,7 +7148,7 @@ pgpassfileWarning(PGconn *conn)
 
 		if (sqlstate && strcmp(sqlstate, ERRCODE_INVALID_PASSWORD) == 0)
 			libpq_append_conn_error(conn, "password retrieved from file \"%s\"",
-							  conn->pgpassfile);
+									conn->pgpassfile);
 	}
 }
 
diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index ec62550e385..0c2dae6ed9e 100644
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -1444,7 +1444,7 @@ PQsendQueryInternal(PGconn *conn, const char *query, bool newQuery)
 	if (conn->pipelineStatus != PQ_PIPELINE_OFF)
 	{
 		libpq_append_conn_error(conn, "%s not allowed in pipeline mode",
-						  "PQsendQuery");
+								"PQsendQuery");
 		return 0;
 	}
 
@@ -1512,7 +1512,7 @@ PQsendQueryParams(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1558,7 +1558,7 @@ PQsendPrepare(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1652,7 +1652,7 @@ PQsendQueryPrepared(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -2099,10 +2099,9 @@ PQgetResult(PGconn *conn)
 
 			/*
 			 * We're about to return the NULL that terminates the round of
-			 * results from the current query; prepare to send the results
-			 * of the next query, if any, when we're called next.  If there's
-			 * no next element in the command queue, this gets us in IDLE
-			 * state.
+			 * results from the current query; prepare to send the results of
+			 * the next query, if any, when we're called next.  If there's no
+			 * next element in the command queue, this gets us in IDLE state.
 			 */
 			pqPipelineProcessQueue(conn);
 			res = NULL;			/* query is complete */
@@ -3047,6 +3046,7 @@ pqPipelineProcessQueue(PGconn *conn)
 			return;
 
 		case PGASYNC_IDLE:
+
 			/*
 			 * If we're in IDLE mode and there's some command in the queue,
 			 * get us into PIPELINE_IDLE mode and process normally.  Otherwise
diff --git a/src/interfaces/libpq/fe-lobj.c b/src/interfaces/libpq/fe-lobj.c
index 4cb6a468597..206266fd043 100644
--- a/src/interfaces/libpq/fe-lobj.c
+++ b/src/interfaces/libpq/fe-lobj.c
@@ -142,7 +142,7 @@ lo_truncate(PGconn *conn, int fd, size_t len)
 	if (conn->lobjfuncs->fn_lo_truncate == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate");
+								"lo_truncate");
 		return -1;
 	}
 
@@ -205,7 +205,7 @@ lo_truncate64(PGconn *conn, int fd, pg_int64 len)
 	if (conn->lobjfuncs->fn_lo_truncate64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate64");
+								"lo_truncate64");
 		return -1;
 	}
 
@@ -395,7 +395,7 @@ lo_lseek64(PGconn *conn, int fd, pg_int64 offset, int whence)
 	if (conn->lobjfuncs->fn_lo_lseek64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek64");
+								"lo_lseek64");
 		return -1;
 	}
 
@@ -485,7 +485,7 @@ lo_create(PGconn *conn, Oid lobjId)
 	if (conn->lobjfuncs->fn_lo_create == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_create");
+								"lo_create");
 		return InvalidOid;
 	}
 
@@ -558,7 +558,7 @@ lo_tell64(PGconn *conn, int fd)
 	if (conn->lobjfuncs->fn_lo_tell64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell64");
+								"lo_tell64");
 		return -1;
 	}
 
@@ -667,7 +667,7 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 	if (fd < 0)
 	{							/* error */
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -723,8 +723,8 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not read from file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -778,8 +778,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -799,8 +799,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 			/* deliberately overwrite any error from lo_close */
 			pqClearConnErrorState(conn);
 			libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-							  filename,
-							  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+									filename,
+									strerror_r(save_errno, sebuf, sizeof(sebuf)));
 			return -1;
 		}
 	}
@@ -822,7 +822,7 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 	if (close(fd) != 0 && result >= 0)
 	{
 		libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		result = -1;
 	}
 
@@ -954,56 +954,56 @@ lo_initialize(PGconn *conn)
 	if (lobjfuncs->fn_lo_open == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_open");
+								"lo_open");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_close == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_close");
+								"lo_close");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_creat == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_creat");
+								"lo_creat");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_unlink == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_unlink");
+								"lo_unlink");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_lseek == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek");
+								"lo_lseek");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_tell == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell");
+								"lo_tell");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_read == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "loread");
+								"loread");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_write == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lowrite");
+								"lowrite");
 		free(lobjfuncs);
 		return -1;
 	}
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 3653a1a8a62..660cdec93c9 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -749,8 +749,8 @@ retry4:
 	 */
 definitelyEOF:
 	libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-					   "\tThis probably means the server terminated abnormally\n"
-					   "\tbefore or while processing the request.");
+							"\tThis probably means the server terminated abnormally\n"
+							"\tbefore or while processing the request.");
 
 	/* Come here if lower-level code already set a suitable errorMessage */
 definitelyFailed:
@@ -1067,7 +1067,7 @@ pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s() failed: %s", "select",
-						  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 	}
 
 	return result;
@@ -1280,7 +1280,7 @@ libpq_ngettext(const char *msgid, const char *msgid_plural, unsigned long n)
  * newline.
  */
 void
-libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
+libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
@@ -1309,7 +1309,7 @@ libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
  * format should not end with a newline.
  */
 void
-libpq_append_conn_error(PGconn *conn, const char *fmt, ...)
+libpq_append_conn_error(PGconn *conn, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index 8ab6a884165..b79d74f7489 100644
--- a/src/interfaces/libpq/fe-protocol3.c
+++ b/src/interfaces/libpq/fe-protocol3.c
@@ -466,7 +466,7 @@ static void
 handleSyncLoss(PGconn *conn, char id, int msgLength)
 {
 	libpq_append_conn_error(conn, "lost synchronization with server: got message type \"%c\", length %d",
-					  id, msgLength);
+							id, msgLength);
 	/* build an error result holding the error message */
 	pqSaveErrorResult(conn);
 	conn->asyncStatus = PGASYNC_READY;	/* drop out of PQgetResult wait loop */
diff --git a/src/interfaces/libpq/fe-secure-common.c b/src/interfaces/libpq/fe-secure-common.c
index de115b37649..3ecc7bf6159 100644
--- a/src/interfaces/libpq/fe-secure-common.c
+++ b/src/interfaces/libpq/fe-secure-common.c
@@ -226,7 +226,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 		 * wrong given the subject matter.
 		 */
 		libpq_append_conn_error(conn, "certificate contains IP address with invalid length %zu",
-						  iplen);
+								iplen);
 		return -1;
 	}
 
@@ -235,7 +235,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 	if (!addrstr)
 	{
 		libpq_append_conn_error(conn, "could not convert certificate's IP address to string: %s",
-						  strerror_r(errno, sebuf, sizeof(sebuf)));
+								strerror_r(errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -292,7 +292,7 @@ pq_verify_peer_name_matches_certificate(PGconn *conn)
 		else if (names_examined == 1)
 		{
 			libpq_append_conn_error(conn, "server certificate for \"%s\" does not match host name \"%s\"",
-							  first_name, host);
+									first_name, host);
 		}
 		else
 		{
diff --git a/src/interfaces/libpq/fe-secure-gssapi.c b/src/interfaces/libpq/fe-secure-gssapi.c
index 6220e4a1014..bed6e62435b 100644
--- a/src/interfaces/libpq/fe-secure-gssapi.c
+++ b/src/interfaces/libpq/fe-secure-gssapi.c
@@ -213,8 +213,8 @@ pg_GSS_write(PGconn *conn, const void *ptr, size_t len)
 		if (output.length > PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "client tried to send oversize GSSAPI packet (%zu > %zu)",
-							  (size_t) output.length,
-							  PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
+									(size_t) output.length,
+									PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			goto cleanup;
 		}
@@ -349,8 +349,8 @@ pg_GSS_read(PGconn *conn, void *ptr, size_t len)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			return -1;
 		}
@@ -588,8 +588,8 @@ pqsecure_open_gss(PGconn *conn)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			return PGRES_POLLING_FAILED;
 		}
 
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index 983536de251..ab2cbf045b8 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -213,12 +213,12 @@ rloop:
 				if (result_errno == EPIPE ||
 					result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -313,12 +313,12 @@ pgtls_write(PGconn *conn, const void *ptr, size_t len)
 				result_errno = SOCK_ERRNO;
 				if (result_errno == EPIPE || result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -410,7 +410,7 @@ pgtls_get_peer_certificate_hash(PGconn *conn, size_t *len)
 			if (algo_type == NULL)
 			{
 				libpq_append_conn_error(conn, "could not find digest for NID %s",
-								  OBJ_nid2sn(algo_nid));
+										OBJ_nid2sn(algo_nid));
 				return NULL;
 			}
 			break;
@@ -962,7 +962,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_min_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for minimum SSL protocol version",
-							  conn->ssl_min_protocol_version);
+									conn->ssl_min_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -988,7 +988,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_max_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for maximum SSL protocol version",
-							  conn->ssl_max_protocol_version);
+									conn->ssl_max_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1032,7 +1032,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read root certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1084,10 +1084,10 @@ initialize_SSL(PGconn *conn)
 			 */
 			if (fnbuf[0] == '\0')
 				libpq_append_conn_error(conn, "could not get home directory to locate root certificate file\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.");
+										"Either provide the file or change sslmode to disable server certificate verification.");
 			else
 				libpq_append_conn_error(conn, "root certificate file \"%s\" does not exist\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
+										"Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1117,7 +1117,7 @@ initialize_SSL(PGconn *conn)
 		if (errno != ENOENT && errno != ENOTDIR)
 		{
 			libpq_append_conn_error(conn, "could not open certificate file \"%s\": %s",
-							  fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
+									fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1135,7 +1135,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1234,7 +1234,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				free(engine_str);
 				return -1;
@@ -1245,7 +1245,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not initialize SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				ENGINE_free(conn->engine);
 				conn->engine = NULL;
@@ -1260,7 +1260,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not read private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1273,7 +1273,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1310,10 +1310,10 @@ initialize_SSL(PGconn *conn)
 		{
 			if (errno == ENOENT)
 				libpq_append_conn_error(conn, "certificate present, but not private key file \"%s\"",
-								  fnbuf);
+										fnbuf);
 			else
 				libpq_append_conn_error(conn, "could not stat private key file \"%s\": %m",
-								  fnbuf);
+										fnbuf);
 			return -1;
 		}
 
@@ -1321,7 +1321,7 @@ initialize_SSL(PGconn *conn)
 		if (!S_ISREG(buf.st_mode))
 		{
 			libpq_append_conn_error(conn, "private key file \"%s\" is not a regular file",
-							  fnbuf);
+									fnbuf);
 			return -1;
 		}
 
@@ -1378,7 +1378,7 @@ initialize_SSL(PGconn *conn)
 			if (SSL_use_PrivateKey_file(conn->ssl, fnbuf, SSL_FILETYPE_ASN1) != 1)
 			{
 				libpq_append_conn_error(conn, "could not load private key file \"%s\": %s",
-								  fnbuf, err);
+										fnbuf, err);
 				SSLerrfree(err);
 				return -1;
 			}
@@ -1394,7 +1394,7 @@ initialize_SSL(PGconn *conn)
 		char	   *err = SSLerrmessage(ERR_get_error());
 
 		libpq_append_conn_error(conn, "certificate does not match private key file \"%s\": %s",
-						  fnbuf, err);
+								fnbuf, err);
 		SSLerrfree(err);
 		return -1;
 	}
@@ -1447,7 +1447,7 @@ open_client_SSL(PGconn *conn)
 
 					if (r == -1)
 						libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-										  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					else
 						libpq_append_conn_error(conn, "SSL SYSCALL error: EOF detected");
 					pgtls_close(conn);
@@ -1489,12 +1489,12 @@ open_client_SSL(PGconn *conn)
 						case SSL_R_VERSION_TOO_LOW:
 #endif
 							libpq_append_conn_error(conn, "This may indicate that the server does not support any SSL protocol version between %s and %s.",
-											  conn->ssl_min_protocol_version ?
-											  conn->ssl_min_protocol_version :
-											  MIN_OPENSSL_TLS_VERSION,
-											  conn->ssl_max_protocol_version ?
-											  conn->ssl_max_protocol_version :
-											  MAX_OPENSSL_TLS_VERSION);
+													conn->ssl_min_protocol_version ?
+													conn->ssl_min_protocol_version :
+													MIN_OPENSSL_TLS_VERSION,
+													conn->ssl_max_protocol_version ?
+													conn->ssl_max_protocol_version :
+													MAX_OPENSSL_TLS_VERSION);
 							break;
 						default:
 							break;
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index 66e401bf3d9..8069e381424 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -255,14 +255,14 @@ pqsecure_raw_read(PGconn *conn, void *ptr, size_t len)
 			case EPIPE:
 			case ECONNRESET:
 				libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-								   "\tThis probably means the server terminated abnormally\n"
-								   "\tbefore or while processing the request.");
+										"\tThis probably means the server terminated abnormally\n"
+										"\tbefore or while processing the request.");
 				break;
 
 			default:
 				libpq_append_conn_error(conn, "could not receive data from server: %s",
-								  SOCK_STRERROR(result_errno,
-												sebuf, sizeof(sebuf)));
+										SOCK_STRERROR(result_errno,
+													  sebuf, sizeof(sebuf)));
 				break;
 		}
 	}
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index d94b648ea5b..712d572373c 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -888,8 +888,8 @@ extern char *libpq_ngettext(const char *msgid, const char *msgid_plural, unsigne
  */
 #undef _
 
-extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...) pg_attribute_printf(2, 3);
-extern void libpq_append_conn_error(PGconn *conn, const char *fmt, ...) pg_attribute_printf(2, 3);
+extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...) pg_attribute_printf(2, 3);
+extern void libpq_append_conn_error(PGconn *conn, const char *fmt,...) pg_attribute_printf(2, 3);
 
 /*
  * These macros are needed to let error-handling code be portable between
-- 
2.34.1

From 71bce9441ed2ba4311cbbcb0fa51f5d89766b701 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Fri, 13 Jan 2023 17:11:00 +0100
Subject: [PATCH v7 4/4] Share prng state between all PGconns in process

Instead of having a PRNG state per connection this adds a process wide
prng state that is protected by a mutex.
---
 src/interfaces/libpq/fe-connect.c | 37 ++++++++++++++++++++++++++-----
 src/interfaces/libpq/libpq-int.h  |  1 -
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 69ed891703a..ec974ac6b84 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -442,6 +442,10 @@ static bool parse_int_param(const char *value, int *result, PGconn *conn,
 /* global variable because fe-auth.c needs to access it */
 pgthreadlock_t pg_g_threadlock = default_threadlock;
 
+static pglock_t prng_lock = PGLOCK_INITIALIZER;
+static bool prng_seed_set = false;
+static pg_prng_state prng_state;
+
 
 /*
  *		pqDropConnection
@@ -1028,16 +1032,25 @@ parse_comma_separated_list(char **startptr, bool *more)
 static bool
 libpq_prng_init(PGconn *conn)
 {
+	if (!pglock(&prng_lock))
+		return false;
+
+	if (likely(prng_seed_set))
+		return pgunlock(&prng_lock);
+
 	if (unlikely(conn->randomseed))
 	{
 		int			rseed;
 
 		if (!parse_int_param(conn->randomseed, &rseed, conn, "random_seed"))
+		{
+			pgunlock(&prng_lock);
 			return false;
+		}
 
-		pg_prng_seed(&conn->prng_state, rseed);
+		pg_prng_seed(&prng_state, rseed);
 	}
-	else if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	else if (unlikely(!pg_prng_strong_seed(&prng_state)))
 	{
 		uint64		rseed;
 		time_t		now = time(NULL);
@@ -1053,8 +1066,12 @@ libpq_prng_init(PGconn *conn)
 			((uint64) now << 12) ^
 			((uint64) now >> 20);
 
-		pg_prng_seed(&conn->prng_state, rseed);
+		pg_prng_seed(&prng_state, rseed);
 	}
+
+	prng_seed_set = true;
+	if (!pgunlock(&prng_lock))
+		return false;
 	return true;
 }
 
@@ -1477,6 +1494,9 @@ connectOptions2(PGconn *conn)
 		if (!libpq_prng_init(conn))
 			return false;
 
+		if (!pglock(&prng_lock))
+			return false;
+
 		/*
 		 * Shuffle connhost with a Durstenfeld/Knuth version of the
 		 * Fisher-Yates shuffle. Source:
@@ -1484,12 +1504,14 @@ connectOptions2(PGconn *conn)
 		 */
 		for (i = conn->nconnhost - 1; i > 0; i--)
 		{
-			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			int			j = pg_prng_uint64_range(&prng_state, 0, i);
 			pg_conn_host temp = conn->connhost[j];
 
 			conn->connhost[j] = conn->connhost[i];
 			conn->connhost[i] = temp;
 		}
+		if (!pgunlock(&prng_lock))
+			return false;
 	}
 
 	/*
@@ -4175,6 +4197,9 @@ store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
 
 	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
 	{
+		if (!pglock(&prng_lock))
+			return false;
+
 		/*
 		 * Shuffle addr with a Durstenfeld/Knuth version of the Fisher-Yates
 		 * shuffle. Source:
@@ -4185,12 +4210,14 @@ store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
 		 */
 		for (int i = conn->naddr - 1; i > 0; i--)
 		{
-			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			int			j = pg_prng_uint64_range(&prng_state, 0, i);
 			AddrInfo	temp = conn->addr[j];
 
 			conn->addr[j] = conn->addr[i];
 			conn->addr[i] = temp;
 		}
+		if (!pgunlock(&prng_lock))
+			return false;
 	}
 	return true;
 }
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 01dd4190f33..0ecac062090 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -492,7 +492,6 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
-	pg_prng_state prng_state;	/* prng state for load balancing connections */
 
 
 	/* Buffer for data received from backend and not yet processed */
-- 
2.34.1

From c92a730bff697d7e2ce694013ca677bcd947e3c6 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <github-tech@jeltef.nl>
Date: Mon, 12 Sep 2022 09:44:06 +0200
Subject: [PATCH v7 2/4] Support load balancing in libpq

This adds support for load balancing to libpq using the newly added
load_balance_hosts parameter. When setting the load_balance_hosts
parameter to random, hosts and addresses will be connected to in a
random order. This then results in load balancing across these
hosts/addresses if multiple clients do this at the same time.

This patch implements two levels of random load balancing:
1. The given hosts are randomly shuffled, before resolving them
    one-by-one.
2. Once a host its addresses get resolved, those addresses are shuffled,
    before trying to connect to them one-by-one.
---
 .cirrus.yml                               |  14 ++
 doc/src/sgml/libpq.sgml                   |  69 +++++++
 src/include/libpq/pqcomm.h                |   6 +
 src/interfaces/libpq/fe-connect.c         | 215 ++++++++++++++++++----
 src/interfaces/libpq/libpq-int.h          |  21 ++-
 src/interfaces/libpq/meson.build          |   1 +
 src/interfaces/libpq/t/003_loadbalance.pl | 167 +++++++++++++++++
 7 files changed, 460 insertions(+), 33 deletions(-)
 create mode 100644 src/interfaces/libpq/t/003_loadbalance.pl

diff --git a/.cirrus.yml b/.cirrus.yml
index 69837bcd5ad..f71e93451fa 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -308,6 +308,14 @@ task:
     mkdir -m 770 /tmp/cores
     chown root:postgres /tmp/cores
     sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core'
+
+  setup_hosts_file_script: |
+    cat >> /etc/hosts <<-EOF
+      127.0.0.1 pg-loadbalancetest
+      127.0.0.2 pg-loadbalancetest
+      127.0.0.3 pg-loadbalancetest
+    EOF
+
   setup_additional_packages_script: |
     #apt-get update
     #DEBIAN_FRONTEND=noninteractive apt-get -y install ...
@@ -557,6 +565,12 @@ task:
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
+  setup_hosts_file_script: |
+    echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    type c:\Windows\System32\Drivers\etc\hosts
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 0e7ae70c706..c540554ade7 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1964,6 +1964,75 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="libpq-connect-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls the order in which the client tries to connect to the available
+        hosts and addresses. It's typically used in combination with multiple
+        host names or a DNS record that returns multiple IPs. This parameter be
+        used in combination with <xref linkend="libpq-connect-target-session-attrs"/>
+        to, for example, load balance over stanby servers only. Once successfully
+        connected, subsequent queries on the returned connection will all be
+        sent to the same server. There are currently two modes:
+        <variablelist>
+         <varlistentry>
+          <term><literal>disable</literal> (default)</term>
+          <listitem>
+           <para>
+            Hosts are tried in the order in which they are provided and
+            addresses are tried in the order they are received from DNS or a
+            hosts file.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>random</literal></term>
+          <listitem>
+           <para>
+            The provided hosts and the addresses that they resolve to are
+            tried in random order. This value is mostly useful when opening
+            multiple connections at the same time, possibly from different
+            machines. This way connections can be load balanced across multiple
+            Postgres servers.
+           </para>
+           <para>
+            This algorithm uses two levels of random choices: First the hosts
+            will be resolved in random order. Then before resolving the next
+            host, all resolved addresses for the current host will be tried in
+            random order. This behaviour can lead to non-uniform address
+            selection in certain cases, for instance when some hosts resolve to
+            more addresses than others. So if you want uniform load balancing,
+            this is something to keep in mind. However, non-uniform load
+            balancing also can be used to your advantage, e.g. by providing the
+            hostname of a larger server multiple times in the host string so it
+            gets more connections.
+           </para>
+           <para>
+            When using this value it's recommended to also configure a reasonable
+            value for <xref linkend="libpq-connect-connect-timeout"/>. Because then,
+            if one of the nodes that are used for load balancing is not responding,
+            a new node will be tried.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-random-seed" xreflabel="random_seed">
+      <term><literal>random_seed</literal></term>
+      <listitem>
+       <para>
+        Sets the random seed that is used by <xref linkend="libpq-connect-load-balance-hosts"/>
+        to randomize the host order. This option is mostly useful when running
+        tests that require a stable random order.
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
    </para>
   </sect2>
diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index 66ba359390f..ee28e223bd7 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+} AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 773e9e1f3a2..18a07d810dc 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -123,6 +123,7 @@ static int	ldapServiceLookup(const char *purl, PQconninfoOption *options,
 #define DefaultChannelBinding	"disable"
 #endif
 #define DefaultTargetSessionAttrs	"any"
+#define DefaultLoadBalanceHosts	"disable"
 #ifdef USE_SSL
 #define DefaultSSLMode "prefer"
 #else
@@ -341,6 +342,15 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Target-Session-Attrs", "", 15, /* sizeof("prefer-standby") = 15 */
 	offsetof(struct pg_conn, target_session_attrs)},
 
+	{"load_balance_hosts", "PGLOADBALANCEHOSTS",
+		DefaultLoadBalanceHosts, NULL,
+		"Load-Balance-Hosts", "", 8,	/* sizeof("disable") = 8 */
+	offsetof(struct pg_conn, load_balance_hosts)},
+
+	{"random_seed", NULL, NULL, NULL,
+		"Random-Seed", "", 10,	/* strlen(INT32_MAX) == 10 */
+	offsetof(struct pg_conn, randomseed)},
+
 	/* Terminating entry --- MUST BE LAST */
 	{NULL, NULL, NULL, NULL,
 	NULL, NULL, 0}
@@ -379,6 +389,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *connstr,
@@ -424,6 +435,8 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static bool parse_int_param(const char *value, int *result, PGconn *conn,
+							const char *context);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1007,6 +1020,44 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on timestamp and PID.
+ */
+static bool
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(conn->randomseed))
+	{
+		int			rseed;
+
+		if (!parse_int_param(conn->randomseed, &rseed, conn, "random_seed"))
+			return false;
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	else if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		time_t		now = time(NULL);
+
+		/*
+		 * Since PIDs and timestamps tend to change more frequently in their
+		 * least significant bits, shift the timestamp left to allow a larger
+		 * total number of seeds in a given time period.  Since that would
+		 * leave only 20 bits of the timestamp that cycle every ~1 second,
+		 * also mix in some higher bits.
+		 */
+		rseed = ((uint64) getpid()) ^
+			((uint64) now << 12) ^
+			((uint64) now >> 20);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	return true;
+}
+
 /*
  *		connectOptions2
  *
@@ -1400,6 +1451,47 @@ connectOptions2(PGconn *conn)
 	else
 		conn->target_server_type = SERVER_TYPE_ANY;
 
+	/*
+	 * validate load_balance_hosts option, and set load_balance_type
+	 */
+	if (conn->load_balance_hosts)
+	{
+		if (strcmp(conn->load_balance_hosts, "disable") == 0)
+			conn->load_balance_type = LOAD_BALANCE_DISABLE;
+		else if (strcmp(conn->load_balance_hosts, "random") == 0)
+			conn->load_balance_type = LOAD_BALANCE_RANDOM;
+		else
+		{
+			conn->status = CONNECTION_BAD;
+			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
+									"load_balance_hosts",
+									conn->load_balance_hosts);
+			return false;
+		}
+	}
+	else
+		conn->load_balance_type = LOAD_BALANCE_DISABLE;
+
+	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+	{
+		if (!libpq_prng_init(conn))
+			return false;
+
+		/*
+		 * Shuffle connhost with a Durstenfeld/Knuth version of the
+		 * Fisher-Yates shuffle. Source:
+		 * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
+		 */
+		for (i = conn->nconnhost - 1; i > 0; i--)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
 	/*
 	 * Resolve special "auto" client_encoding from the locale
 	 */
@@ -2077,7 +2169,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2121,11 +2213,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2272,9 +2364,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2287,6 +2379,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2327,7 +2420,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2350,8 +2443,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
 											ch->host, gai_strerror(ret));
@@ -2362,8 +2455,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
 											ch->hostaddr, gai_strerror(ret));
@@ -2372,7 +2465,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2387,8 +2480,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
 											portstr, gai_strerror(ret));
@@ -2397,8 +2490,14 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		if (!store_conn_addrinfo(conn, addrlist))
+		{
+			pg_freeaddrinfo_all(hint.ai_family, addrlist);
+			libpq_append_conn_error(conn, "out of memory");
+			goto error_return;
+		}
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2455,30 +2554,29 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2494,7 +2592,7 @@ keep_going:						/* We will come back to here until there is
 						conn->connip = strdup(host_addr);
 
 					/* Try to create the socket */
-					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
+					conn->sock = socket(addr_cur->family, SOCK_STREAM, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2505,7 +2603,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2531,7 +2629,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2558,7 +2656,7 @@ keep_going:						/* We will come back to here until there is
 					}
 #endif							/* F_SETFD */
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2650,8 +2748,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4035,12 +4133,68 @@ freePGconn(PGconn *conn)
 	free(conn->outBuffer);
 	free(conn->rowBuf);
 	free(conn->target_session_attrs);
+	free(conn->load_balance_hosts);
+	free(conn->randomseed);
 	termPQExpBuffer(&conn->errorMessage);
 	termPQExpBuffer(&conn->workBuffer);
 
 	free(conn);
 }
 
+/*
+ * Copies over the AddrInfos from addrlist to the PGconn.
+ */
+static bool
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+		return false;
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+	{
+		/*
+		 * Shuffle addr with a Durstenfeld/Knuth version of the Fisher-Yates
+		 * shuffle. Source:
+		 * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm
+		 *
+		 * We don't need to initialize conn->prng_state here, because that
+		 * already happened in connectOptions2.
+		 */
+		for (int i = conn->naddr - 1; i > 0; i--)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			AddrInfo	temp = conn->addr[j];
+
+			conn->addr[j] = conn->addr[i];
+			conn->addr[i] = temp;
+		}
+	}
+	return true;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4048,11 +4202,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 712d572373c..86dd1d6d405 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -82,6 +82,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -242,6 +244,13 @@ typedef enum
 	SERVER_TYPE_PREFER_STANDBY_PASS2	/* second pass - behaves same as ANY */
 } PGTargetServerType;
 
+/* Target server type (decoded value of load_balance_hosts) */
+typedef enum
+{
+	LOAD_BALANCE_DISABLE = 0,	/* Use the existing host order (default) */
+	LOAD_BALANCE_RANDOM,		/* Read-write server */
+}			PGLoadBalanceType;
+
 /* Boolean value plus a not-known state, for GUCs we might have to fetch */
 typedef enum
 {
@@ -396,6 +405,8 @@ struct pg_conn
 	char	   *ssl_min_protocol_version;	/* minimum TLS protocol version */
 	char	   *ssl_max_protocol_version;	/* maximum TLS protocol version */
 	char	   *target_session_attrs;	/* desired session properties */
+	char	   *load_balance_hosts; /* load balance over hosts */
+	char	   *randomseed;		/* seed for randomization of load balancing */
 
 	/* Optional file to write trace info to */
 	FILE	   *Pfdebug;
@@ -459,10 +470,14 @@ struct pg_conn
 
 	/* Transient state needed while establishing connection */
 	PGTargetServerType target_server_type;	/* desired session properties */
+	PGLoadBalanceType load_balance_type;	/* desired load balancing
+											 * algorithm */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
+	int			naddr;			/* number of addresses returned by getaddrinfo */
+	int			whichaddr;		/* the address currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	int			addrlist_family;	/* needed to know how to free addrlist */
 	bool		send_appname;	/* okay to send application_name? */
 
@@ -477,6 +492,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index 573fd9b6ea4..52b327500c7 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -116,6 +116,7 @@ tests += {
     'tests': [
       't/001_uri.pl',
       't/002_api.pl',
+      't/003_loadbalance.pl',
     ],
     'env': {'with_ssl': get_option('ssl')},
   },
diff --git a/src/interfaces/libpq/t/003_loadbalance.pl b/src/interfaces/libpq/t/003_loadbalance.pl
new file mode 100644
index 00000000000..1b4e8fd8133
--- /dev/null
+++ b/src/interfaces/libpq/t/003_loadbalance.pl
@@ -0,0 +1,167 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use File::Spec::Functions 'catfile';
+use Test::More;
+
+# This tests two different methods of load balancing from libpq
+# 1. Load balancing by providing multiple host and port combinations in the
+#    libpq connection string.
+# 2. By using a hosts file where hostname maps to multiple different IP
+#    addresses. Regular Postgres users wouldn't usually use such a host file,
+#    but this is the easiest way to immitate behaviour of a DNS server that
+#    returns multiple IP addresses for the same DNS record.
+#
+# Testing method 1 is supported on all platforms and works out of the box. But
+# testing method 2 has some more requirements, both on the platform and on the
+# initial setup. If any of these requirements are not met, then method 2 is
+# simply not tested.
+#
+# The requirements to test method 2 are as follows:
+# 1. Windows or Linux should be used.
+# 2. The OS hosts file at /etc/hosts or c:\Windows\System32\Drivers\etc\hosts
+#    should contain the following contents:
+#
+# 127.0.0.1 pg-loadbalancetest
+# 127.0.0.2 pg-loadbalancetest
+# 127.0.0.3 pg-loadbalancetest
+#
+#
+# Windows or Linux are required to test method 2 because these OSes allow
+# binding to 127.0.0.2 and 127.0.0.3 addresess by default, but other OSes
+# don't. We need to bind to different IP addresses, so that we can use these
+# different IP addresses in the hosts file.
+#
+# The hosts file needs to be prepared before running this test. We don't do it
+# on the fly, because it requires root permissions to change the hosts file. In
+# CI we set up the previously mentioned rules in the hosts file, so that this
+# load balancing method is tested.
+
+
+# Cluster setup which is shared for testing both load balancing methods
+my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os;
+
+if ($can_bind_to_127_0_0_2)
+{
+	$PostgreSQL::Test::Cluster::use_tcp = 1;
+	$PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1';
+}
+my $port = PostgreSQL::Test::Cluster::get_free_port();
+my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port);
+my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# Start the tests for load balancing method 1
+my $hostlist = $node1->host . ',' . $node2->host . ',' . $node3->host;
+my $portlist = "$port,$port,$port";
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=123",
+	"seed 123 selects node 1 first",
+	sql => "SELECT 'connect1'",
+	log_like => [qr/statement: SELECT 'connect1'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=123",
+	"seed 123 does not select node 2 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=123",
+	"seed 123 does not select node 3 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 selects node 3 first",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 1 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node3->stop();
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does select node 1 second",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 second",
+	sql => "SELECT 'connect3'",
+	log_unlike => [qr/statement: SELECT 'connect3'/]);
+
+$node3->start();
+
+# Checks for the requirements for testing load balancing method 2
+if (!$can_bind_to_127_0_0_2) {
+	# The OS requirement is not met
+	done_testing();
+	exit;
+}
+
+my $hosts_path;
+if ($windows_os) {
+	$hosts_path = 'c:\Windows\System32\Drivers\etc\hosts';
+}
+else
+{
+	$hosts_path = '/etc/hosts';
+}
+
+my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path);
+
+if ($hosts_content !~ m/pg-loadbalancetest/) {
+	# Host file is not prepared for this test
+	done_testing();
+	exit;
+}
+
+# Start the tests for load balancing method 2
+$node2->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=44",
+	"seed 44 selects node 2 first",
+	sql => "SELECT 'connect4'",
+	log_like => [qr/statement: SELECT 'connect4'/]);
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=44",
+	"seed 44 does not select node 1 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=44",
+	"seed 44 does not select node 3 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node2->stop();
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=44",
+	"seed 44 does select node 1 second",
+	sql => "SELECT 'connect5'",
+	log_like => [qr/statement: SELECT 'connect5'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=44",
+	"seed 44 does not select node 3 second",
+	sql => "SELECT 'connect5'",
+	log_unlike => [qr/statement: SELECT 'connect5'/]);
+
+done_testing();
-- 
2.34.1

From 4904b1aa4fac90f9677a26b9a882f613e728edeb Mon Sep 17 00:00:00 2001
From: Jelte Fennema <github-tech@jeltef.nl>
Date: Mon, 12 Sep 2022 09:44:06 +0200
Subject: [PATCH v8 3/3] Support load balancing in libpq

This adds support for load balancing to libpq using the newly added
load_balance_hosts parameter. When setting the load_balance_hosts
parameter to random, hosts and addresses will be connected to in a
random order. This then results in load balancing across these
hosts/addresses if multiple clients do this at the same time.

This patch implements two levels of random load balancing:
1. The given hosts are randomly shuffled, before resolving them
    one-by-one.
2. Once a host its addresses get resolved, those addresses are shuffled,
    before trying to connect to them one-by-one.
---
 .cirrus.yml                                   |  16 ++-
 doc/src/sgml/libpq.sgml                       |  69 ++++++++++
 doc/src/sgml/regress.sgml                     |  11 +-
 src/interfaces/libpq/fe-connect.c             | 120 ++++++++++++++++++
 src/interfaces/libpq/libpq-int.h              |  18 ++-
 src/interfaces/libpq/meson.build              |   2 +
 .../libpq/t/003_loadbalance_host_list.pl      |  76 +++++++++++
 src/interfaces/libpq/t/004_loadbalance_dns.pl | 103 +++++++++++++++
 8 files changed, 412 insertions(+), 3 deletions(-)
 create mode 100644 src/interfaces/libpq/t/003_loadbalance_host_list.pl
 create mode 100644 src/interfaces/libpq/t/004_loadbalance_dns.pl

diff --git a/.cirrus.yml b/.cirrus.yml
index 69837bcd5ad..e332fbf0f8f 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -25,7 +25,7 @@ env:
   MTEST_ARGS: --print-errorlogs --no-rebuild -C build
   PGCTLTIMEOUT: 120 # avoids spurious failures during parallel tests
   TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
-  PG_TEST_EXTRA: kerberos ldap ssl
+  PG_TEST_EXTRA: kerberos ldap ssl loadbalance
 
 
 # What files to preserve in case tests fail
@@ -308,6 +308,14 @@ task:
     mkdir -m 770 /tmp/cores
     chown root:postgres /tmp/cores
     sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core'
+
+  setup_hosts_file_script: |
+    cat >> /etc/hosts <<-EOF
+      127.0.0.1 pg-loadbalancetest
+      127.0.0.2 pg-loadbalancetest
+      127.0.0.3 pg-loadbalancetest
+    EOF
+
   setup_additional_packages_script: |
     #apt-get update
     #DEBIAN_FRONTEND=noninteractive apt-get -y install ...
@@ -557,6 +565,12 @@ task:
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
+  setup_hosts_file_script: |
+    echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    type c:\Windows\System32\Drivers\etc\hosts
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 0e7ae70c706..c540554ade7 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1964,6 +1964,75 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="libpq-connect-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls the order in which the client tries to connect to the available
+        hosts and addresses. It's typically used in combination with multiple
+        host names or a DNS record that returns multiple IPs. This parameter be
+        used in combination with <xref linkend="libpq-connect-target-session-attrs"/>
+        to, for example, load balance over stanby servers only. Once successfully
+        connected, subsequent queries on the returned connection will all be
+        sent to the same server. There are currently two modes:
+        <variablelist>
+         <varlistentry>
+          <term><literal>disable</literal> (default)</term>
+          <listitem>
+           <para>
+            Hosts are tried in the order in which they are provided and
+            addresses are tried in the order they are received from DNS or a
+            hosts file.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>random</literal></term>
+          <listitem>
+           <para>
+            The provided hosts and the addresses that they resolve to are
+            tried in random order. This value is mostly useful when opening
+            multiple connections at the same time, possibly from different
+            machines. This way connections can be load balanced across multiple
+            Postgres servers.
+           </para>
+           <para>
+            This algorithm uses two levels of random choices: First the hosts
+            will be resolved in random order. Then before resolving the next
+            host, all resolved addresses for the current host will be tried in
+            random order. This behaviour can lead to non-uniform address
+            selection in certain cases, for instance when some hosts resolve to
+            more addresses than others. So if you want uniform load balancing,
+            this is something to keep in mind. However, non-uniform load
+            balancing also can be used to your advantage, e.g. by providing the
+            hostname of a larger server multiple times in the host string so it
+            gets more connections.
+           </para>
+           <para>
+            When using this value it's recommended to also configure a reasonable
+            value for <xref linkend="libpq-connect-connect-timeout"/>. Because then,
+            if one of the nodes that are used for load balancing is not responding,
+            a new node will be tried.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-random-seed" xreflabel="random_seed">
+      <term><literal>random_seed</literal></term>
+      <listitem>
+       <para>
+        Sets the random seed that is used by <xref linkend="libpq-connect-load-balance-hosts"/>
+        to randomize the host order. This option is mostly useful when running
+        tests that require a stable random order.
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
    </para>
   </sect2>
diff --git a/doc/src/sgml/regress.sgml b/doc/src/sgml/regress.sgml
index 117d097390c..6fe254023fd 100644
--- a/doc/src/sgml/regress.sgml
+++ b/doc/src/sgml/regress.sgml
@@ -256,7 +256,7 @@ make check-world -j8 >/dev/null
    <varname>PG_TEST_EXTRA</varname> to a whitespace-separated list, for
    example:
 <programlisting>
-make check-world PG_TEST_EXTRA='kerberos ldap ssl'
+make check-world PG_TEST_EXTRA='kerberos ldap ssl loadbalance'
 </programlisting>
    The following values are currently supported:
    <variablelist>
@@ -290,6 +290,15 @@ make check-world PG_TEST_EXTRA='kerberos ldap ssl'
      </listitem>
     </varlistentry>
 
+    <varlistentry>
+     <term><literal>loadbalance</literal></term>
+     <listitem>
+      <para>
+       Runs the test <filename>src/interfaces/libpq/t/004_loadbalance_dns.pl</filename>.  This opens TCP/IP listen sockets.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry>
      <term><literal>wal_consistency_checking</literal></term>
      <listitem>
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 46afe127f15..98b13f57a07 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -123,6 +123,7 @@ static int	ldapServiceLookup(const char *purl, PQconninfoOption *options,
 #define DefaultChannelBinding	"disable"
 #endif
 #define DefaultTargetSessionAttrs	"any"
+#define DefaultLoadBalanceHosts	"disable"
 #ifdef USE_SSL
 #define DefaultSSLMode "prefer"
 #else
@@ -341,6 +342,15 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Target-Session-Attrs", "", 15, /* sizeof("prefer-standby") = 15 */
 	offsetof(struct pg_conn, target_session_attrs)},
 
+	{"load_balance_hosts", "PGLOADBALANCEHOSTS",
+		DefaultLoadBalanceHosts, NULL,
+		"Load-Balance-Hosts", "", 8,	/* sizeof("disable") = 8 */
+	offsetof(struct pg_conn, load_balance_hosts)},
+
+	{"random_seed", NULL, NULL, NULL,
+		"Random-Seed", "", 10,	/* strlen(INT32_MAX) == 10 */
+	offsetof(struct pg_conn, randomseed)},
+
 	/* Terminating entry --- MUST BE LAST */
 	{NULL, NULL, NULL, NULL,
 	NULL, NULL, 0}
@@ -425,6 +435,8 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static bool parse_int_param(const char *value, int *result, PGconn *conn,
+							const char *context);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1008,6 +1020,40 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on timestamp and PID.
+ */
+static bool
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(conn->randomseed))
+	{
+		int			rseed;
+
+		if (!parse_int_param(conn->randomseed, &rseed, conn, "random_seed"))
+			return false;
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	else if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		struct timeval tval = {0};
+
+		gettimeofday(&tval, NULL);
+
+		rseed = ((uint64) conn) ^
+			((uint64) getpid()) ^
+			((uint64) tval.tv_usec) ^
+			((uint64) tval.tv_sec);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	return true;
+}
+
 /*
  *		connectOptions2
  *
@@ -1401,6 +1447,51 @@ connectOptions2(PGconn *conn)
 	else
 		conn->target_server_type = SERVER_TYPE_ANY;
 
+	/*
+	 * validate load_balance_hosts option, and set load_balance_type
+	 */
+	if (conn->load_balance_hosts)
+	{
+		if (strcmp(conn->load_balance_hosts, "disable") == 0)
+			conn->load_balance_type = LOAD_BALANCE_DISABLE;
+		else if (strcmp(conn->load_balance_hosts, "random") == 0)
+			conn->load_balance_type = LOAD_BALANCE_RANDOM;
+		else
+		{
+			conn->status = CONNECTION_BAD;
+			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
+									"load_balance_hosts",
+									conn->load_balance_hosts);
+			return false;
+		}
+	}
+	else
+		conn->load_balance_type = LOAD_BALANCE_DISABLE;
+
+	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+	{
+		if (!libpq_prng_init(conn))
+			return false;
+
+		/*
+		 * This is the "inside-out" variant of the Fisher-Yates shuffle
+		 * algorithm. Notionally, we append each new value to the array and
+		 * then swap it with a randomly-chosen array element (possibly
+		 * including itself, else we fail to generate permutations with the
+		 * last integer last).  The swap step can be optimized by combining it
+		 * with the insertion.
+		 */
+		for (i = 1; i < conn->nconnhost; i++)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			if (j < i)			/* avoid fetching undefined data if j=i */
+				conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
 	/*
 	 * Resolve special "auto" client_encoding from the locale
 	 */
@@ -2407,6 +2498,33 @@ keep_going:						/* We will come back to here until there is
 		}
 		pg_freeaddrinfo_all(hint.ai_family, addrlist);
 
+		/*
+		 * If random load balancing is enabled we shuffle the addresses.
+		 */
+		if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+		{
+			/*
+			 * This is the "inside-out" variant of the Fisher-Yates shuffle
+			 * algorithm. Notionally, we append each new value to the array
+			 * and then swap it with a randomly-chosen array element (possibly
+			 * including itself, else we fail to generate permutations with
+			 * the last integer last).  The swap step can be optimized by
+			 * combining it with the insertion.
+			 *
+			 * We don't need to initialize conn->prng_state here, because that
+			 * already happened in connectOptions2.
+			 */
+			for (int i = 1; i < conn->naddr; i++)
+			{
+				int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+				AddrInfo	temp = conn->addr[j];
+
+				if (j < i)		/* avoid fetching undefined data if j=i */
+					conn->addr[j] = conn->addr[i];
+				conn->addr[i] = temp;
+			}
+		}
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -4042,6 +4160,8 @@ freePGconn(PGconn *conn)
 	free(conn->outBuffer);
 	free(conn->rowBuf);
 	free(conn->target_session_attrs);
+	free(conn->load_balance_hosts);
+	free(conn->randomseed);
 	termPQExpBuffer(&conn->errorMessage);
 	termPQExpBuffer(&conn->workBuffer);
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 940db7ecc8c..36c05b9a712 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -26,7 +26,8 @@
 #include <netdb.h>
 #include <sys/socket.h>
 #include <time.h>
-#ifndef WIN32
+/* MinGW has sys/time.h, but MSVC doesn't */
+#ifndef _MSC_VER
 #include <sys/time.h>
 #endif
 
@@ -82,6 +83,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -242,6 +245,13 @@ typedef enum
 	SERVER_TYPE_PREFER_STANDBY_PASS2	/* second pass - behaves same as ANY */
 } PGTargetServerType;
 
+/* Target server type (decoded value of load_balance_hosts) */
+typedef enum
+{
+	LOAD_BALANCE_DISABLE = 0,	/* Use the existing host order (default) */
+	LOAD_BALANCE_RANDOM,		/* Read-write server */
+}			PGLoadBalanceType;
+
 /* Boolean value plus a not-known state, for GUCs we might have to fetch */
 typedef enum
 {
@@ -396,6 +406,8 @@ struct pg_conn
 	char	   *ssl_min_protocol_version;	/* minimum TLS protocol version */
 	char	   *ssl_max_protocol_version;	/* maximum TLS protocol version */
 	char	   *target_session_attrs;	/* desired session properties */
+	char	   *load_balance_hosts; /* load balance over hosts */
+	char	   *randomseed;		/* seed for randomization of load balancing */
 
 	/* Optional file to write trace info to */
 	FILE	   *Pfdebug;
@@ -459,6 +471,8 @@ struct pg_conn
 
 	/* Transient state needed while establishing connection */
 	PGTargetServerType target_server_type;	/* desired session properties */
+	PGLoadBalanceType load_balance_type;	/* desired load balancing
+											 * algorithm */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
 	int			naddr;			/* number of addresses returned by getaddrinfo */
@@ -479,6 +493,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index 573fd9b6ea4..edebb014362 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -116,6 +116,8 @@ tests += {
     'tests': [
       't/001_uri.pl',
       't/002_api.pl',
+      't/003_loadbalance_host_list.pl',
+      't/004_loadbalance_dns.pl',
     ],
     'env': {'with_ssl': get_option('ssl')},
   },
diff --git a/src/interfaces/libpq/t/003_loadbalance_host_list.pl b/src/interfaces/libpq/t/003_loadbalance_host_list.pl
new file mode 100644
index 00000000000..547b7d34fa4
--- /dev/null
+++ b/src/interfaces/libpq/t/003_loadbalance_host_list.pl
@@ -0,0 +1,76 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests load balancing across the list of different hosts in the host
+# parameter of the connection string.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $node1 = PostgreSQL::Test::Cluster->new('node1');
+my $node2 = PostgreSQL::Test::Cluster->new('node2', own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# Start the tests for load balancing method 1
+my $hostlist = $node1->host . ',' . $node2->host . ',' . $node3->host;
+my $portlist = $node1->port . ',' . $node2->port . ',' . $node3->port;
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 selects node 1 first",
+	sql => "SELECT 'connect1'",
+	log_like => [qr/statement: SELECT 'connect1'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 does not select node 2 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 does not select node 3 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 selects node 3 first",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 1 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node3->stop();
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does select node 1 second",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 second",
+	sql => "SELECT 'connect3'",
+	log_unlike => [qr/statement: SELECT 'connect3'/]);
+
+$node3->start();
+
+done_testing();
+
diff --git a/src/interfaces/libpq/t/004_loadbalance_dns.pl b/src/interfaces/libpq/t/004_loadbalance_dns.pl
new file mode 100644
index 00000000000..2512c41c466
--- /dev/null
+++ b/src/interfaces/libpq/t/004_loadbalance_dns.pl
@@ -0,0 +1,103 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests loadbalancing based on a DNS entry that contains multiple records
+# for different IPs. Since setting up a DNS server is more effort than we
+# consider reasonable to run this test, this situation is instead immitated by
+# using a hosts file where a single hostname maps to multiple different IP
+# addresses. This test requires the adminstrator to add the following lines to
+# the hosts file (if we detect that this hasn't happend we skip the test):
+#
+# 127.0.0.1 pg-loadbalancetest
+# 127.0.0.2 pg-loadbalancetest
+# 127.0.0.3 pg-loadbalancetest
+#
+# Windows or Linux are required to run this test because these OSes allow
+# binding to 127.0.0.2 and 127.0.0.3 addresess by default, but other OSes
+# don't. We need to bind to different IP addresses, so that we can use these
+# different IP addresses in the hosts file.
+#
+# The hosts file needs to be prepared before running this test. We don't do it
+# on the fly, because it requires root permissions to change the hosts file. In
+# CI we set up the previously mentioned rules in the hosts file, so that this
+# load balancing method is tested.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os;
+
+# Checks for the requirements for testing load balancing method 2
+if (!$can_bind_to_127_0_0_2) {
+	plan skip_all => "OS could not bind to 127.0.0.2"
+}
+
+my $hosts_path;
+if ($windows_os) {
+	$hosts_path = 'c:\Windows\System32\Drivers\etc\hosts';
+}
+else
+{
+	$hosts_path = '/etc/hosts';
+}
+
+my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path);
+
+if ($hosts_content !~ m/pg-loadbalancetest/) {
+	# Host file is not prepared for this test
+	plan skip_all => "hosts file was not prepared for DNS load balance test"
+}
+
+if ($ENV{PG_TEST_EXTRA} !~ /\bloadbalance\b/)
+{
+	plan skip_all => 'Potentially unsafe test loadbalance not enabled in PG_TEST_EXTRA';
+}
+
+$PostgreSQL::Test::Cluster::use_tcp = 1;
+$PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1';
+my $port = PostgreSQL::Test::Cluster::get_free_port();
+my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port);
+my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+$node2->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 selects node 2 first",
+	sql => "SELECT 'connect4'",
+	log_like => [qr/statement: SELECT 'connect4'/]);
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 1 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 3 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node2->stop();
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does select node 1 second",
+	sql => "SELECT 'connect5'",
+	log_like => [qr/statement: SELECT 'connect5'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 3 second",
+	sql => "SELECT 'connect5'",
+	log_unlike => [qr/statement: SELECT 'connect5'/]);
+
+done_testing();
-- 
2.34.1

From ed14a0414122717d69d19bf8378206bf3a8ed6a2 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 25 Jan 2023 10:22:41 +0100
Subject: [PATCH v8 2/3] Refactor libpq to store addrinfo in a libpq owned
 array

This refactors libpq to copy addrinfos returned by getaddrinfo to
memory owned by us. This refactoring is useful for two upcoming patches,
which need to change the addrinfo list in some way. Doing that with the
original addrinfo list is risky since we don't control how memory is
freed. Also changing the contents of a C array is quite a bit easier
than changing a linked list.

As a nice side effect of this refactor the is that mechanism for
iteration over addresses in PQconnectPoll is now identical to its
iteration over hosts.
---
 src/include/libpq/pqcomm.h        |   6 ++
 src/interfaces/libpq/fe-connect.c | 107 +++++++++++++++++++++---------
 src/interfaces/libpq/libpq-int.h  |   6 +-
 src/tools/pgindent/typedefs.list  |   1 +
 4 files changed, 87 insertions(+), 33 deletions(-)

diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index 66ba359390f..ee28e223bd7 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+} AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 773e9e1f3a2..46afe127f15 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -379,6 +379,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *connstr,
@@ -2077,7 +2078,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2121,11 +2122,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2272,9 +2273,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2287,6 +2288,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2327,7 +2329,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2350,8 +2352,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
 											ch->host, gai_strerror(ret));
@@ -2362,8 +2364,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
 											ch->hostaddr, gai_strerror(ret));
@@ -2372,7 +2374,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2387,8 +2389,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
 											portstr, gai_strerror(ret));
@@ -2397,8 +2399,14 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		if (!store_conn_addrinfo(conn, addrlist))
+		{
+			pg_freeaddrinfo_all(hint.ai_family, addrlist);
+			libpq_append_conn_error(conn, "out of memory");
+			goto error_return;
+		}
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2455,30 +2463,29 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2494,7 +2501,7 @@ keep_going:						/* We will come back to here until there is
 						conn->connip = strdup(host_addr);
 
 					/* Try to create the socket */
-					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
+					conn->sock = socket(addr_cur->family, SOCK_STREAM, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2505,7 +2512,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2531,7 +2538,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2558,7 +2565,7 @@ keep_going:						/* We will come back to here until there is
 					}
 #endif							/* F_SETFD */
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2650,8 +2657,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4041,6 +4048,45 @@ freePGconn(PGconn *conn)
 	free(conn);
 }
 
+/*
+ * Copies over the addrinfos from addrlist to the PGconn. The reason we do this
+ * so that we can edit the resulting list as we please, because now the memory
+ * is owned by us. Changing the original addrinfo directly is risky, since we
+ * don't control how the memory is freed and by changing it we might confuse
+ * the implementation of freeaddrinfo.
+ */
+static bool
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+		return false;
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	return true;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4048,11 +4094,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 712d572373c..940db7ecc8c 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -461,8 +461,10 @@ struct pg_conn
 	PGTargetServerType target_server_type;	/* desired session properties */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
+	int			naddr;			/* number of addresses returned by getaddrinfo */
+	int			whichaddr;		/* the address currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	int			addrlist_family;	/* needed to know how to free addrlist */
 	bool		send_appname;	/* okay to send application_name? */
 
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 51484ca7e2f..6762f4dc70f 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -26,6 +26,7 @@ AcquireSampleRowsFunc
 ActionList
 ActiveSnapshotElt
 AddForeignUpdateTargets_function
+AddrInfo
 AffixNode
 AffixNodeData
 AfterTriggerEvent
-- 
2.34.1

From 556359f17858cb2ac251a8180fbed8191948c9bd Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 30 Nov 2022 10:07:19 +0100
Subject: [PATCH v8 1/3] libpq: Run pgindent after a9e9a9f32b3

It seems that pgindent was not run after the error handling refactor in
commit a9e9a9f32b35edf129c88e8b929ef223f8511f59. This fixes that and
also addresses a few other things pgindent wanted to change in libpq.
---
 src/interfaces/libpq/fe-auth-scram.c     |   2 +-
 src/interfaces/libpq/fe-auth.c           |   8 +-
 src/interfaces/libpq/fe-connect.c        | 124 +++++++++++------------
 src/interfaces/libpq/fe-exec.c           |  16 +--
 src/interfaces/libpq/fe-lobj.c           |  42 ++++----
 src/interfaces/libpq/fe-misc.c           |  10 +-
 src/interfaces/libpq/fe-protocol3.c      |   2 +-
 src/interfaces/libpq/fe-secure-common.c  |   6 +-
 src/interfaces/libpq/fe-secure-gssapi.c  |  12 +--
 src/interfaces/libpq/fe-secure-openssl.c |  64 ++++++------
 src/interfaces/libpq/fe-secure.c         |   8 +-
 src/interfaces/libpq/libpq-int.h         |   4 +-
 12 files changed, 149 insertions(+), 149 deletions(-)

diff --git a/src/interfaces/libpq/fe-auth-scram.c b/src/interfaces/libpq/fe-auth-scram.c
index 9c42ea4f819..12c3d0bc333 100644
--- a/src/interfaces/libpq/fe-auth-scram.c
+++ b/src/interfaces/libpq/fe-auth-scram.c
@@ -716,7 +716,7 @@ read_server_final_message(fe_scram_state *state, char *input)
 			return false;
 		}
 		libpq_append_conn_error(conn, "error received from server in SCRAM exchange: %s",
-						   errmsg);
+								errmsg);
 		return false;
 	}
 
diff --git a/src/interfaces/libpq/fe-auth.c b/src/interfaces/libpq/fe-auth.c
index 9afc6f19b9a..ab454e6cd02 100644
--- a/src/interfaces/libpq/fe-auth.c
+++ b/src/interfaces/libpq/fe-auth.c
@@ -73,7 +73,7 @@ pg_GSS_continue(PGconn *conn, int payloadlen)
 		if (!ginbuf.value)
 		{
 			libpq_append_conn_error(conn, "out of memory allocating GSSAPI buffer (%d)",
-							  payloadlen);
+									payloadlen);
 			return STATUS_ERROR;
 		}
 		if (pqGetnchar(ginbuf.value, payloadlen, conn))
@@ -223,7 +223,7 @@ pg_SSPI_continue(PGconn *conn, int payloadlen)
 		if (!inputbuf)
 		{
 			libpq_append_conn_error(conn, "out of memory allocating SSPI buffer (%d)",
-							  payloadlen);
+									payloadlen);
 			return STATUS_ERROR;
 		}
 		if (pqGetnchar(inputbuf, payloadlen, conn))
@@ -623,7 +623,7 @@ pg_SASL_continue(PGconn *conn, int payloadlen, bool final)
 	if (!challenge)
 	{
 		libpq_append_conn_error(conn, "out of memory allocating SASL buffer (%d)",
-						  payloadlen);
+								payloadlen);
 		return STATUS_ERROR;
 	}
 
@@ -1277,7 +1277,7 @@ PQencryptPasswordConn(PGconn *conn, const char *passwd, const char *user,
 	else
 	{
 		libpq_append_conn_error(conn, "unrecognized password encryption algorithm \"%s\"",
-						  algorithm);
+								algorithm);
 		return NULL;
 	}
 
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 50b5df3490b..773e9e1f3a2 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -1079,7 +1079,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "could not match %d host names to %d hostaddr values",
-							   count_comma_separated_elems(conn->pghost), conn->nconnhost);
+									count_comma_separated_elems(conn->pghost), conn->nconnhost);
 			return false;
 		}
 	}
@@ -1159,7 +1159,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "could not match %d port numbers to %d hosts",
-							   count_comma_separated_elems(conn->pgport), conn->nconnhost);
+									count_comma_separated_elems(conn->pgport), conn->nconnhost);
 			return false;
 		}
 	}
@@ -1248,7 +1248,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "channel_binding", conn->channel_binding);
+									"channel_binding", conn->channel_binding);
 			return false;
 		}
 	}
@@ -1273,7 +1273,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "sslmode", conn->sslmode);
+									"sslmode", conn->sslmode);
 			return false;
 		}
 
@@ -1293,7 +1293,7 @@ connectOptions2(PGconn *conn)
 			case 'v':			/* "verify-ca" or "verify-full" */
 				conn->status = CONNECTION_BAD;
 				libpq_append_conn_error(conn, "sslmode value \"%s\" invalid when SSL support is not compiled in",
-								   conn->sslmode);
+										conn->sslmode);
 				return false;
 		}
 #endif
@@ -1313,16 +1313,16 @@ connectOptions2(PGconn *conn)
 	{
 		conn->status = CONNECTION_BAD;
 		libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-						   "ssl_min_protocol_version",
-						   conn->ssl_min_protocol_version);
+								"ssl_min_protocol_version",
+								conn->ssl_min_protocol_version);
 		return false;
 	}
 	if (!sslVerifyProtocolVersion(conn->ssl_max_protocol_version))
 	{
 		conn->status = CONNECTION_BAD;
 		libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-						   "ssl_max_protocol_version",
-						   conn->ssl_max_protocol_version);
+								"ssl_max_protocol_version",
+								conn->ssl_max_protocol_version);
 		return false;
 	}
 
@@ -1359,7 +1359,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "gssencmode value \"%s\" invalid when GSSAPI support is not compiled in",
-							   conn->gssencmode);
+									conn->gssencmode);
 			return false;
 		}
 #endif
@@ -1392,8 +1392,8 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "target_session_attrs",
-							   conn->target_session_attrs);
+									"target_session_attrs",
+									conn->target_session_attrs);
 			return false;
 		}
 	}
@@ -1609,7 +1609,7 @@ connectNoDelay(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "could not set socket to TCP no delay mode: %s",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1787,7 +1787,7 @@ parse_int_param(const char *value, int *result, PGconn *conn,
 
 error:
 	libpq_append_conn_error(conn, "invalid integer value \"%s\" for connection option \"%s\"",
-					   value, context);
+							value, context);
 	return false;
 }
 
@@ -1816,9 +1816,9 @@ setKeepalivesIdle(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   PG_TCP_KEEPALIVE_IDLE_STR,
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								PG_TCP_KEEPALIVE_IDLE_STR,
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1850,9 +1850,9 @@ setKeepalivesInterval(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_KEEPINTVL",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_KEEPINTVL",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1885,9 +1885,9 @@ setKeepalivesCount(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_KEEPCNT",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_KEEPCNT",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1949,8 +1949,8 @@ prepKeepalivesWin32(PGconn *conn)
 	if (!setKeepalivesWin32(conn->sock, idle, interval))
 	{
 		libpq_append_conn_error(conn, "%s(%s) failed: error code %d",
-						  "WSAIoctl", "SIO_KEEPALIVE_VALS",
-						  WSAGetLastError());
+								"WSAIoctl", "SIO_KEEPALIVE_VALS",
+								WSAGetLastError());
 		return 0;
 	}
 	return 1;
@@ -1983,9 +1983,9 @@ setTCPUserTimeout(PGconn *conn)
 		char		sebuf[256];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_USER_TIMEOUT",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_USER_TIMEOUT",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -2354,7 +2354,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
-									   ch->host, gai_strerror(ret));
+											ch->host, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2366,7 +2366,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
-									   ch->hostaddr, gai_strerror(ret));
+											ch->hostaddr, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2377,8 +2377,8 @@ keep_going:						/* We will come back to here until there is
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
 					libpq_append_conn_error(conn, "Unix-domain socket path \"%s\" is too long (maximum %d bytes)",
-									   portstr,
-									   (int) (UNIXSOCK_PATH_BUFLEN - 1));
+											portstr,
+											(int) (UNIXSOCK_PATH_BUFLEN - 1));
 					goto keep_going;
 				}
 
@@ -2391,7 +2391,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
-									   portstr, gai_strerror(ret));
+											portstr, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2513,7 +2513,7 @@ keep_going:						/* We will come back to here until there is
 						}
 						emitHostIdentityInfo(conn, host_addr);
 						libpq_append_conn_error(conn, "could not create socket: %s",
-										   SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2543,7 +2543,7 @@ keep_going:						/* We will come back to here until there is
 					if (!pg_set_noblock(conn->sock))
 					{
 						libpq_append_conn_error(conn, "could not set socket to nonblocking mode: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						conn->try_next_addr = true;
 						goto keep_going;
 					}
@@ -2552,7 +2552,7 @@ keep_going:						/* We will come back to here until there is
 					if (fcntl(conn->sock, F_SETFD, FD_CLOEXEC) == -1)
 					{
 						libpq_append_conn_error(conn, "could not set socket to close-on-exec mode: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						conn->try_next_addr = true;
 						goto keep_going;
 					}
@@ -2581,9 +2581,9 @@ keep_going:						/* We will come back to here until there is
 											(char *) &on, sizeof(on)) < 0)
 						{
 							libpq_append_conn_error(conn, "%s(%s) failed: %s",
-											   "setsockopt",
-											   "SO_KEEPALIVE",
-											   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+													"setsockopt",
+													"SO_KEEPALIVE",
+													SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 							err = 1;
 						}
 						else if (!setKeepalivesIdle(conn)
@@ -2708,7 +2708,7 @@ keep_going:						/* We will come back to here until there is
 							   (char *) &optval, &optlen) == -1)
 				{
 					libpq_append_conn_error(conn, "could not get socket error status: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					goto error_return;
 				}
 				else if (optval != 0)
@@ -2735,7 +2735,7 @@ keep_going:						/* We will come back to here until there is
 								&conn->laddr.salen) < 0)
 				{
 					libpq_append_conn_error(conn, "could not get client address from socket: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					goto error_return;
 				}
 
@@ -2775,7 +2775,7 @@ keep_going:						/* We will come back to here until there is
 							libpq_append_conn_error(conn, "requirepeer parameter is not supported on this platform");
 						else
 							libpq_append_conn_error(conn, "could not get peer credentials: %s",
-											   strerror_r(errno, sebuf, sizeof(sebuf)));
+													strerror_r(errno, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2788,7 +2788,7 @@ keep_going:						/* We will come back to here until there is
 					if (strcmp(remote_username, conn->requirepeer) != 0)
 					{
 						libpq_append_conn_error(conn, "requirepeer specifies \"%s\", but actual peer user name is \"%s\"",
-										   conn->requirepeer, remote_username);
+												conn->requirepeer, remote_username);
 						free(remote_username);
 						goto error_return;
 					}
@@ -2829,7 +2829,7 @@ keep_going:						/* We will come back to here until there is
 					if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
 					{
 						libpq_append_conn_error(conn, "could not send GSSAPI negotiation packet: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2840,7 +2840,7 @@ keep_going:						/* We will come back to here until there is
 				else if (!conn->gctx && conn->gssencmode[0] == 'r')
 				{
 					libpq_append_conn_error(conn,
-									   "GSSAPI encryption required but was impossible (possibly no credential cache, no server support, or using a local socket)");
+											"GSSAPI encryption required but was impossible (possibly no credential cache, no server support, or using a local socket)");
 					goto error_return;
 				}
 #endif
@@ -2882,7 +2882,7 @@ keep_going:						/* We will come back to here until there is
 					if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
 					{
 						libpq_append_conn_error(conn, "could not send SSL negotiation packet: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 					/* Ok, wait for response */
@@ -2911,7 +2911,7 @@ keep_going:						/* We will come back to here until there is
 				if (pqPacketSend(conn, 0, startpacket, packetlen) != STATUS_OK)
 				{
 					libpq_append_conn_error(conn, "could not send startup packet: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					free(startpacket);
 					goto error_return;
 				}
@@ -3012,7 +3012,7 @@ keep_going:						/* We will come back to here until there is
 					else
 					{
 						libpq_append_conn_error(conn, "received invalid response to SSL negotiation: %c",
-										   SSLok);
+												SSLok);
 						goto error_return;
 					}
 				}
@@ -3123,7 +3123,7 @@ keep_going:						/* We will come back to here until there is
 					else if (gss_ok != 'G')
 					{
 						libpq_append_conn_error(conn, "received invalid response to GSSAPI negotiation: %c",
-										   gss_ok);
+												gss_ok);
 						goto error_return;
 					}
 				}
@@ -3201,7 +3201,7 @@ keep_going:						/* We will come back to here until there is
 				if (!(beresp == 'R' || beresp == 'v' || beresp == 'E'))
 				{
 					libpq_append_conn_error(conn, "expected authentication request from server, but received %c",
-									   beresp);
+											beresp);
 					goto error_return;
 				}
 
@@ -3216,17 +3216,17 @@ keep_going:						/* We will come back to here until there is
 				 * Try to validate message length before using it.
 				 * Authentication requests can't be very large, although GSS
 				 * auth requests may not be that small.  Same for
-				 * NegotiateProtocolVersion.  Errors can be a
-				 * little larger, but not huge.  If we see a large apparent
-				 * length in an error, it means we're really talking to a
-				 * pre-3.0-protocol server; cope.  (Before version 14, the
-				 * server also used the old protocol for errors that happened
-				 * before processing the startup packet.)
+				 * NegotiateProtocolVersion.  Errors can be a little larger,
+				 * but not huge.  If we see a large apparent length in an
+				 * error, it means we're really talking to a pre-3.0-protocol
+				 * server; cope.  (Before version 14, the server also used the
+				 * old protocol for errors that happened before processing the
+				 * startup packet.)
 				 */
 				if ((beresp == 'R' || beresp == 'v') && (msgLength < 8 || msgLength > 2000))
 				{
 					libpq_append_conn_error(conn, "expected authentication request from server, but received %c",
-									   beresp);
+											beresp);
 					goto error_return;
 				}
 
@@ -3705,7 +3705,7 @@ keep_going:						/* We will come back to here until there is
 
 				/* Append error report to conn->errorMessage. */
 				libpq_append_conn_error(conn, "\"%s\" failed",
-								  "SHOW transaction_read_only");
+										"SHOW transaction_read_only");
 
 				/* Close connection politely. */
 				conn->status = CONNECTION_OK;
@@ -3755,7 +3755,7 @@ keep_going:						/* We will come back to here until there is
 
 				/* Append error report to conn->errorMessage. */
 				libpq_append_conn_error(conn, "\"%s\" failed",
-								  "SELECT pg_is_in_recovery()");
+										"SELECT pg_is_in_recovery()");
 
 				/* Close connection politely. */
 				conn->status = CONNECTION_OK;
@@ -3768,8 +3768,8 @@ keep_going:						/* We will come back to here until there is
 
 		default:
 			libpq_append_conn_error(conn,
-							   "invalid connection state %d, probably indicative of memory corruption",
-							  conn->status);
+									"invalid connection state %d, probably indicative of memory corruption",
+									conn->status);
 			goto error_return;
 	}
 
@@ -7148,7 +7148,7 @@ pgpassfileWarning(PGconn *conn)
 
 		if (sqlstate && strcmp(sqlstate, ERRCODE_INVALID_PASSWORD) == 0)
 			libpq_append_conn_error(conn, "password retrieved from file \"%s\"",
-							  conn->pgpassfile);
+									conn->pgpassfile);
 	}
 }
 
diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index ec62550e385..0c2dae6ed9e 100644
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -1444,7 +1444,7 @@ PQsendQueryInternal(PGconn *conn, const char *query, bool newQuery)
 	if (conn->pipelineStatus != PQ_PIPELINE_OFF)
 	{
 		libpq_append_conn_error(conn, "%s not allowed in pipeline mode",
-						  "PQsendQuery");
+								"PQsendQuery");
 		return 0;
 	}
 
@@ -1512,7 +1512,7 @@ PQsendQueryParams(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1558,7 +1558,7 @@ PQsendPrepare(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1652,7 +1652,7 @@ PQsendQueryPrepared(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -2099,10 +2099,9 @@ PQgetResult(PGconn *conn)
 
 			/*
 			 * We're about to return the NULL that terminates the round of
-			 * results from the current query; prepare to send the results
-			 * of the next query, if any, when we're called next.  If there's
-			 * no next element in the command queue, this gets us in IDLE
-			 * state.
+			 * results from the current query; prepare to send the results of
+			 * the next query, if any, when we're called next.  If there's no
+			 * next element in the command queue, this gets us in IDLE state.
 			 */
 			pqPipelineProcessQueue(conn);
 			res = NULL;			/* query is complete */
@@ -3047,6 +3046,7 @@ pqPipelineProcessQueue(PGconn *conn)
 			return;
 
 		case PGASYNC_IDLE:
+
 			/*
 			 * If we're in IDLE mode and there's some command in the queue,
 			 * get us into PIPELINE_IDLE mode and process normally.  Otherwise
diff --git a/src/interfaces/libpq/fe-lobj.c b/src/interfaces/libpq/fe-lobj.c
index 4cb6a468597..206266fd043 100644
--- a/src/interfaces/libpq/fe-lobj.c
+++ b/src/interfaces/libpq/fe-lobj.c
@@ -142,7 +142,7 @@ lo_truncate(PGconn *conn, int fd, size_t len)
 	if (conn->lobjfuncs->fn_lo_truncate == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate");
+								"lo_truncate");
 		return -1;
 	}
 
@@ -205,7 +205,7 @@ lo_truncate64(PGconn *conn, int fd, pg_int64 len)
 	if (conn->lobjfuncs->fn_lo_truncate64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate64");
+								"lo_truncate64");
 		return -1;
 	}
 
@@ -395,7 +395,7 @@ lo_lseek64(PGconn *conn, int fd, pg_int64 offset, int whence)
 	if (conn->lobjfuncs->fn_lo_lseek64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek64");
+								"lo_lseek64");
 		return -1;
 	}
 
@@ -485,7 +485,7 @@ lo_create(PGconn *conn, Oid lobjId)
 	if (conn->lobjfuncs->fn_lo_create == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_create");
+								"lo_create");
 		return InvalidOid;
 	}
 
@@ -558,7 +558,7 @@ lo_tell64(PGconn *conn, int fd)
 	if (conn->lobjfuncs->fn_lo_tell64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell64");
+								"lo_tell64");
 		return -1;
 	}
 
@@ -667,7 +667,7 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 	if (fd < 0)
 	{							/* error */
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -723,8 +723,8 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not read from file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -778,8 +778,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -799,8 +799,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 			/* deliberately overwrite any error from lo_close */
 			pqClearConnErrorState(conn);
 			libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-							  filename,
-							  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+									filename,
+									strerror_r(save_errno, sebuf, sizeof(sebuf)));
 			return -1;
 		}
 	}
@@ -822,7 +822,7 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 	if (close(fd) != 0 && result >= 0)
 	{
 		libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		result = -1;
 	}
 
@@ -954,56 +954,56 @@ lo_initialize(PGconn *conn)
 	if (lobjfuncs->fn_lo_open == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_open");
+								"lo_open");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_close == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_close");
+								"lo_close");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_creat == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_creat");
+								"lo_creat");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_unlink == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_unlink");
+								"lo_unlink");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_lseek == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek");
+								"lo_lseek");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_tell == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell");
+								"lo_tell");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_read == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "loread");
+								"loread");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_write == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lowrite");
+								"lowrite");
 		free(lobjfuncs);
 		return -1;
 	}
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 3653a1a8a62..660cdec93c9 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -749,8 +749,8 @@ retry4:
 	 */
 definitelyEOF:
 	libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-					   "\tThis probably means the server terminated abnormally\n"
-					   "\tbefore or while processing the request.");
+							"\tThis probably means the server terminated abnormally\n"
+							"\tbefore or while processing the request.");
 
 	/* Come here if lower-level code already set a suitable errorMessage */
 definitelyFailed:
@@ -1067,7 +1067,7 @@ pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s() failed: %s", "select",
-						  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 	}
 
 	return result;
@@ -1280,7 +1280,7 @@ libpq_ngettext(const char *msgid, const char *msgid_plural, unsigned long n)
  * newline.
  */
 void
-libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
+libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
@@ -1309,7 +1309,7 @@ libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
  * format should not end with a newline.
  */
 void
-libpq_append_conn_error(PGconn *conn, const char *fmt, ...)
+libpq_append_conn_error(PGconn *conn, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index 8ab6a884165..b79d74f7489 100644
--- a/src/interfaces/libpq/fe-protocol3.c
+++ b/src/interfaces/libpq/fe-protocol3.c
@@ -466,7 +466,7 @@ static void
 handleSyncLoss(PGconn *conn, char id, int msgLength)
 {
 	libpq_append_conn_error(conn, "lost synchronization with server: got message type \"%c\", length %d",
-					  id, msgLength);
+							id, msgLength);
 	/* build an error result holding the error message */
 	pqSaveErrorResult(conn);
 	conn->asyncStatus = PGASYNC_READY;	/* drop out of PQgetResult wait loop */
diff --git a/src/interfaces/libpq/fe-secure-common.c b/src/interfaces/libpq/fe-secure-common.c
index de115b37649..3ecc7bf6159 100644
--- a/src/interfaces/libpq/fe-secure-common.c
+++ b/src/interfaces/libpq/fe-secure-common.c
@@ -226,7 +226,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 		 * wrong given the subject matter.
 		 */
 		libpq_append_conn_error(conn, "certificate contains IP address with invalid length %zu",
-						  iplen);
+								iplen);
 		return -1;
 	}
 
@@ -235,7 +235,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 	if (!addrstr)
 	{
 		libpq_append_conn_error(conn, "could not convert certificate's IP address to string: %s",
-						  strerror_r(errno, sebuf, sizeof(sebuf)));
+								strerror_r(errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -292,7 +292,7 @@ pq_verify_peer_name_matches_certificate(PGconn *conn)
 		else if (names_examined == 1)
 		{
 			libpq_append_conn_error(conn, "server certificate for \"%s\" does not match host name \"%s\"",
-							  first_name, host);
+									first_name, host);
 		}
 		else
 		{
diff --git a/src/interfaces/libpq/fe-secure-gssapi.c b/src/interfaces/libpq/fe-secure-gssapi.c
index 6220e4a1014..bed6e62435b 100644
--- a/src/interfaces/libpq/fe-secure-gssapi.c
+++ b/src/interfaces/libpq/fe-secure-gssapi.c
@@ -213,8 +213,8 @@ pg_GSS_write(PGconn *conn, const void *ptr, size_t len)
 		if (output.length > PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "client tried to send oversize GSSAPI packet (%zu > %zu)",
-							  (size_t) output.length,
-							  PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
+									(size_t) output.length,
+									PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			goto cleanup;
 		}
@@ -349,8 +349,8 @@ pg_GSS_read(PGconn *conn, void *ptr, size_t len)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			return -1;
 		}
@@ -588,8 +588,8 @@ pqsecure_open_gss(PGconn *conn)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			return PGRES_POLLING_FAILED;
 		}
 
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index 983536de251..ab2cbf045b8 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -213,12 +213,12 @@ rloop:
 				if (result_errno == EPIPE ||
 					result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -313,12 +313,12 @@ pgtls_write(PGconn *conn, const void *ptr, size_t len)
 				result_errno = SOCK_ERRNO;
 				if (result_errno == EPIPE || result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -410,7 +410,7 @@ pgtls_get_peer_certificate_hash(PGconn *conn, size_t *len)
 			if (algo_type == NULL)
 			{
 				libpq_append_conn_error(conn, "could not find digest for NID %s",
-								  OBJ_nid2sn(algo_nid));
+										OBJ_nid2sn(algo_nid));
 				return NULL;
 			}
 			break;
@@ -962,7 +962,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_min_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for minimum SSL protocol version",
-							  conn->ssl_min_protocol_version);
+									conn->ssl_min_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -988,7 +988,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_max_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for maximum SSL protocol version",
-							  conn->ssl_max_protocol_version);
+									conn->ssl_max_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1032,7 +1032,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read root certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1084,10 +1084,10 @@ initialize_SSL(PGconn *conn)
 			 */
 			if (fnbuf[0] == '\0')
 				libpq_append_conn_error(conn, "could not get home directory to locate root certificate file\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.");
+										"Either provide the file or change sslmode to disable server certificate verification.");
 			else
 				libpq_append_conn_error(conn, "root certificate file \"%s\" does not exist\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
+										"Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1117,7 +1117,7 @@ initialize_SSL(PGconn *conn)
 		if (errno != ENOENT && errno != ENOTDIR)
 		{
 			libpq_append_conn_error(conn, "could not open certificate file \"%s\": %s",
-							  fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
+									fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1135,7 +1135,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1234,7 +1234,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				free(engine_str);
 				return -1;
@@ -1245,7 +1245,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not initialize SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				ENGINE_free(conn->engine);
 				conn->engine = NULL;
@@ -1260,7 +1260,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not read private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1273,7 +1273,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1310,10 +1310,10 @@ initialize_SSL(PGconn *conn)
 		{
 			if (errno == ENOENT)
 				libpq_append_conn_error(conn, "certificate present, but not private key file \"%s\"",
-								  fnbuf);
+										fnbuf);
 			else
 				libpq_append_conn_error(conn, "could not stat private key file \"%s\": %m",
-								  fnbuf);
+										fnbuf);
 			return -1;
 		}
 
@@ -1321,7 +1321,7 @@ initialize_SSL(PGconn *conn)
 		if (!S_ISREG(buf.st_mode))
 		{
 			libpq_append_conn_error(conn, "private key file \"%s\" is not a regular file",
-							  fnbuf);
+									fnbuf);
 			return -1;
 		}
 
@@ -1378,7 +1378,7 @@ initialize_SSL(PGconn *conn)
 			if (SSL_use_PrivateKey_file(conn->ssl, fnbuf, SSL_FILETYPE_ASN1) != 1)
 			{
 				libpq_append_conn_error(conn, "could not load private key file \"%s\": %s",
-								  fnbuf, err);
+										fnbuf, err);
 				SSLerrfree(err);
 				return -1;
 			}
@@ -1394,7 +1394,7 @@ initialize_SSL(PGconn *conn)
 		char	   *err = SSLerrmessage(ERR_get_error());
 
 		libpq_append_conn_error(conn, "certificate does not match private key file \"%s\": %s",
-						  fnbuf, err);
+								fnbuf, err);
 		SSLerrfree(err);
 		return -1;
 	}
@@ -1447,7 +1447,7 @@ open_client_SSL(PGconn *conn)
 
 					if (r == -1)
 						libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-										  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					else
 						libpq_append_conn_error(conn, "SSL SYSCALL error: EOF detected");
 					pgtls_close(conn);
@@ -1489,12 +1489,12 @@ open_client_SSL(PGconn *conn)
 						case SSL_R_VERSION_TOO_LOW:
 #endif
 							libpq_append_conn_error(conn, "This may indicate that the server does not support any SSL protocol version between %s and %s.",
-											  conn->ssl_min_protocol_version ?
-											  conn->ssl_min_protocol_version :
-											  MIN_OPENSSL_TLS_VERSION,
-											  conn->ssl_max_protocol_version ?
-											  conn->ssl_max_protocol_version :
-											  MAX_OPENSSL_TLS_VERSION);
+													conn->ssl_min_protocol_version ?
+													conn->ssl_min_protocol_version :
+													MIN_OPENSSL_TLS_VERSION,
+													conn->ssl_max_protocol_version ?
+													conn->ssl_max_protocol_version :
+													MAX_OPENSSL_TLS_VERSION);
 							break;
 						default:
 							break;
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index 66e401bf3d9..8069e381424 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -255,14 +255,14 @@ pqsecure_raw_read(PGconn *conn, void *ptr, size_t len)
 			case EPIPE:
 			case ECONNRESET:
 				libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-								   "\tThis probably means the server terminated abnormally\n"
-								   "\tbefore or while processing the request.");
+										"\tThis probably means the server terminated abnormally\n"
+										"\tbefore or while processing the request.");
 				break;
 
 			default:
 				libpq_append_conn_error(conn, "could not receive data from server: %s",
-								  SOCK_STRERROR(result_errno,
-												sebuf, sizeof(sebuf)));
+										SOCK_STRERROR(result_errno,
+													  sebuf, sizeof(sebuf)));
 				break;
 		}
 	}
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index d94b648ea5b..712d572373c 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -888,8 +888,8 @@ extern char *libpq_ngettext(const char *msgid, const char *msgid_plural, unsigne
  */
 #undef _
 
-extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...) pg_attribute_printf(2, 3);
-extern void libpq_append_conn_error(PGconn *conn, const char *fmt, ...) pg_attribute_printf(2, 3);
+extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...) pg_attribute_printf(2, 3);
+extern void libpq_append_conn_error(PGconn *conn, const char *fmt,...) pg_attribute_printf(2, 3);
 
 /*
  * These macros are needed to let error-handling code be portable between
-- 
2.34.1

From df38b507278cf2f2dffb564b370b6f07c3116079 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 25 Jan 2023 10:22:41 +0100
Subject: [PATCH v9 2/3] Refactor libpq to store addrinfo in a libpq owned
 array

This refactors libpq to copy addrinfos returned by getaddrinfo to
memory owned by us. This refactoring is useful for two upcoming patches,
which need to change the addrinfo list in some way. Doing that with the
original addrinfo list is risky since we don't control how memory is
freed. Also changing the contents of a C array is quite a bit easier
than changing a linked list.

As a nice side effect of this refactor the is that mechanism for
iteration over addresses in PQconnectPoll is now identical to its
iteration over hosts.
---
 src/include/libpq/pqcomm.h        |   6 ++
 src/interfaces/libpq/fe-connect.c | 107 +++++++++++++++++++++---------
 src/interfaces/libpq/libpq-int.h  |   6 +-
 src/tools/pgindent/typedefs.list  |   1 +
 4 files changed, 87 insertions(+), 33 deletions(-)

diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index 66ba359390f..ee28e223bd7 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+} AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 97e47f05852..41deeee9a63 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -379,6 +379,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *connstr,
@@ -2077,7 +2078,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2121,11 +2122,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2272,9 +2273,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2287,6 +2288,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2327,7 +2329,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2350,8 +2352,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
 											ch->host, gai_strerror(ret));
@@ -2362,8 +2364,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
 											ch->hostaddr, gai_strerror(ret));
@@ -2372,7 +2374,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2387,8 +2389,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
 											portstr, gai_strerror(ret));
@@ -2397,8 +2399,14 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		if (!store_conn_addrinfo(conn, addrlist))
+		{
+			pg_freeaddrinfo_all(hint.ai_family, addrlist);
+			libpq_append_conn_error(conn, "out of memory");
+			goto error_return;
+		}
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2455,30 +2463,29 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2494,7 +2501,7 @@ keep_going:						/* We will come back to here until there is
 						conn->connip = strdup(host_addr);
 
 					/* Try to create the socket */
-					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
+					conn->sock = socket(addr_cur->family, SOCK_STREAM, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2505,7 +2512,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2531,7 +2538,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2558,7 +2565,7 @@ keep_going:						/* We will come back to here until there is
 					}
 #endif							/* F_SETFD */
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2650,8 +2657,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4068,6 +4075,45 @@ freePGconn(PGconn *conn)
 	free(conn);
 }
 
+/*
+ * Copies over the addrinfos from addrlist to the PGconn. The reason we do this
+ * so that we can edit the resulting list as we please, because now the memory
+ * is owned by us. Changing the original addrinfo directly is risky, since we
+ * don't control how the memory is freed and by changing it we might confuse
+ * the implementation of freeaddrinfo.
+ */
+static bool
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+		return false;
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	return true;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4075,11 +4121,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 85289980a11..4d40e8a2fbb 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -461,8 +461,10 @@ struct pg_conn
 	PGTargetServerType target_server_type;	/* desired session properties */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
+	int			naddr;			/* number of addresses returned by getaddrinfo */
+	int			whichaddr;		/* the address currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	int			addrlist_family;	/* needed to know how to free addrlist */
 	bool		send_appname;	/* okay to send application_name? */
 
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 86a9303bf56..fa8881c9d93 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -26,6 +26,7 @@ AcquireSampleRowsFunc
 ActionList
 ActiveSnapshotElt
 AddForeignUpdateTargets_function
+AddrInfo
 AffixNode
 AffixNodeData
 AfterTriggerEvent
-- 
2.34.1

From 94e7d6f9078bdfa0c9421acf3588e5128b9109e5 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <github-tech@jeltef.nl>
Date: Mon, 12 Sep 2022 09:44:06 +0200
Subject: [PATCH v9 3/3] Support load balancing in libpq

This adds support for load balancing to libpq using the newly added
load_balance_hosts parameter. When setting the load_balance_hosts
parameter to random, hosts and addresses will be connected to in a
random order. This then results in load balancing across these
hosts/addresses if multiple clients do this at the same time.

This patch implements two levels of random load balancing:
1. The given hosts are randomly shuffled, before resolving them
    one-by-one.
2. Once a host its addresses get resolved, those addresses are shuffled,
    before trying to connect to them one-by-one.
---
 .cirrus.yml                                   |  16 ++-
 doc/src/sgml/libpq.sgml                       |  69 ++++++++++
 doc/src/sgml/regress.sgml                     |  11 +-
 src/interfaces/libpq/fe-connect.c             | 120 ++++++++++++++++++
 src/interfaces/libpq/libpq-int.h              |  18 ++-
 src/interfaces/libpq/meson.build              |   2 +
 .../libpq/t/003_loadbalance_host_list.pl      |  76 +++++++++++
 src/interfaces/libpq/t/004_loadbalance_dns.pl | 103 +++++++++++++++
 8 files changed, 412 insertions(+), 3 deletions(-)
 create mode 100644 src/interfaces/libpq/t/003_loadbalance_host_list.pl
 create mode 100644 src/interfaces/libpq/t/004_loadbalance_dns.pl

diff --git a/.cirrus.yml b/.cirrus.yml
index f2129787529..51f810a4031 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -25,7 +25,7 @@ env:
   MTEST_ARGS: --print-errorlogs --no-rebuild -C build
   PGCTLTIMEOUT: 120 # avoids spurious failures during parallel tests
   TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
-  PG_TEST_EXTRA: kerberos ldap ssl
+  PG_TEST_EXTRA: kerberos ldap ssl loadbalance
 
 
 # What files to preserve in case tests fail
@@ -314,6 +314,14 @@ task:
     mkdir -m 770 /tmp/cores
     chown root:postgres /tmp/cores
     sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core'
+
+  setup_hosts_file_script: |
+    cat >> /etc/hosts <<-EOF
+      127.0.0.1 pg-loadbalancetest
+      127.0.0.2 pg-loadbalancetest
+      127.0.0.3 pg-loadbalancetest
+    EOF
+
   setup_additional_packages_script: |
     #apt-get update
     #DEBIAN_FRONTEND=noninteractive apt-get -y install ...
@@ -565,6 +573,12 @@ task:
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
+  setup_hosts_file_script: |
+    echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    type c:\Windows\System32\Drivers\etc\hosts
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 3ccd8ff9421..ee5869c9274 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1964,6 +1964,75 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="libpq-connect-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls the order in which the client tries to connect to the available
+        hosts and addresses. It's typically used in combination with multiple
+        host names or a DNS record that returns multiple IPs. This parameter be
+        used in combination with <xref linkend="libpq-connect-target-session-attrs"/>
+        to, for example, load balance over stanby servers only. Once successfully
+        connected, subsequent queries on the returned connection will all be
+        sent to the same server. There are currently two modes:
+        <variablelist>
+         <varlistentry>
+          <term><literal>disable</literal> (default)</term>
+          <listitem>
+           <para>
+            Hosts are tried in the order in which they are provided and
+            addresses are tried in the order they are received from DNS or a
+            hosts file.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>random</literal></term>
+          <listitem>
+           <para>
+            The provided hosts and the addresses that they resolve to are
+            tried in random order. This value is mostly useful when opening
+            multiple connections at the same time, possibly from different
+            machines. This way connections can be load balanced across multiple
+            Postgres servers.
+           </para>
+           <para>
+            This algorithm uses two levels of random choices: First the hosts
+            will be resolved in random order. Then before resolving the next
+            host, all resolved addresses for the current host will be tried in
+            random order. This behaviour can lead to non-uniform address
+            selection in certain cases, for instance when some hosts resolve to
+            more addresses than others. So if you want uniform load balancing,
+            this is something to keep in mind. However, non-uniform load
+            balancing also can be used to your advantage, e.g. by providing the
+            hostname of a larger server multiple times in the host string so it
+            gets more connections.
+           </para>
+           <para>
+            When using this value it's recommended to also configure a reasonable
+            value for <xref linkend="libpq-connect-connect-timeout"/>. Because then,
+            if one of the nodes that are used for load balancing is not responding,
+            a new node will be tried.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-random-seed" xreflabel="random_seed">
+      <term><literal>random_seed</literal></term>
+      <listitem>
+       <para>
+        Sets the random seed that is used by <xref linkend="libpq-connect-load-balance-hosts"/>
+        to randomize the host order. This option is mostly useful when running
+        tests that require a stable random order.
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
    </para>
   </sect2>
diff --git a/doc/src/sgml/regress.sgml b/doc/src/sgml/regress.sgml
index a08c7a78af8..026ac05c755 100644
--- a/doc/src/sgml/regress.sgml
+++ b/doc/src/sgml/regress.sgml
@@ -256,7 +256,7 @@ make check-world -j8 >/dev/null
    <varname>PG_TEST_EXTRA</varname> to a whitespace-separated list, for
    example:
 <programlisting>
-make check-world PG_TEST_EXTRA='kerberos ldap ssl'
+make check-world PG_TEST_EXTRA='kerberos ldap ssl loadbalance'
 </programlisting>
    The following values are currently supported:
    <variablelist>
@@ -290,6 +290,15 @@ make check-world PG_TEST_EXTRA='kerberos ldap ssl'
      </listitem>
     </varlistentry>
 
+    <varlistentry>
+     <term><literal>loadbalance</literal></term>
+     <listitem>
+      <para>
+       Runs the test <filename>src/interfaces/libpq/t/004_loadbalance_dns.pl</filename>.  This opens TCP/IP listen sockets.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry>
      <term><literal>wal_consistency_checking</literal></term>
      <listitem>
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 41deeee9a63..5e214e0b788 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -123,6 +123,7 @@ static int	ldapServiceLookup(const char *purl, PQconninfoOption *options,
 #define DefaultChannelBinding	"disable"
 #endif
 #define DefaultTargetSessionAttrs	"any"
+#define DefaultLoadBalanceHosts	"disable"
 #ifdef USE_SSL
 #define DefaultSSLMode "prefer"
 #else
@@ -341,6 +342,15 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Target-Session-Attrs", "", 15, /* sizeof("prefer-standby") = 15 */
 	offsetof(struct pg_conn, target_session_attrs)},
 
+	{"load_balance_hosts", "PGLOADBALANCEHOSTS",
+		DefaultLoadBalanceHosts, NULL,
+		"Load-Balance-Hosts", "", 8,	/* sizeof("disable") = 8 */
+	offsetof(struct pg_conn, load_balance_hosts)},
+
+	{"random_seed", NULL, NULL, NULL,
+		"Random-Seed", "", 10,	/* strlen(INT32_MAX) == 10 */
+	offsetof(struct pg_conn, randomseed)},
+
 	/* Terminating entry --- MUST BE LAST */
 	{NULL, NULL, NULL, NULL,
 	NULL, NULL, 0}
@@ -425,6 +435,8 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static bool parse_int_param(const char *value, int *result, PGconn *conn,
+							const char *context);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1008,6 +1020,40 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on timestamp and PID.
+ */
+static bool
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(conn->randomseed))
+	{
+		int			rseed;
+
+		if (!parse_int_param(conn->randomseed, &rseed, conn, "random_seed"))
+			return false;
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	else if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		struct timeval tval = {0};
+
+		gettimeofday(&tval, NULL);
+
+		rseed = ((uint64) conn) ^
+			((uint64) getpid()) ^
+			((uint64) tval.tv_usec) ^
+			((uint64) tval.tv_sec);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	return true;
+}
+
 /*
  *		connectOptions2
  *
@@ -1401,6 +1447,51 @@ connectOptions2(PGconn *conn)
 	else
 		conn->target_server_type = SERVER_TYPE_ANY;
 
+	/*
+	 * validate load_balance_hosts option, and set load_balance_type
+	 */
+	if (conn->load_balance_hosts)
+	{
+		if (strcmp(conn->load_balance_hosts, "disable") == 0)
+			conn->load_balance_type = LOAD_BALANCE_DISABLE;
+		else if (strcmp(conn->load_balance_hosts, "random") == 0)
+			conn->load_balance_type = LOAD_BALANCE_RANDOM;
+		else
+		{
+			conn->status = CONNECTION_BAD;
+			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
+									"load_balance_hosts",
+									conn->load_balance_hosts);
+			return false;
+		}
+	}
+	else
+		conn->load_balance_type = LOAD_BALANCE_DISABLE;
+
+	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+	{
+		if (!libpq_prng_init(conn))
+			return false;
+
+		/*
+		 * This is the "inside-out" variant of the Fisher-Yates shuffle
+		 * algorithm. Notionally, we append each new value to the array and
+		 * then swap it with a randomly-chosen array element (possibly
+		 * including itself, else we fail to generate permutations with the
+		 * last integer last).  The swap step can be optimized by combining it
+		 * with the insertion.
+		 */
+		for (i = 1; i < conn->nconnhost; i++)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			if (j < i)			/* avoid fetching undefined data if j=i */
+				conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
 	/*
 	 * Resolve special "auto" client_encoding from the locale
 	 */
@@ -2407,6 +2498,33 @@ keep_going:						/* We will come back to here until there is
 		}
 		pg_freeaddrinfo_all(hint.ai_family, addrlist);
 
+		/*
+		 * If random load balancing is enabled we shuffle the addresses.
+		 */
+		if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+		{
+			/*
+			 * This is the "inside-out" variant of the Fisher-Yates shuffle
+			 * algorithm. Notionally, we append each new value to the array
+			 * and then swap it with a randomly-chosen array element (possibly
+			 * including itself, else we fail to generate permutations with
+			 * the last integer last).  The swap step can be optimized by
+			 * combining it with the insertion.
+			 *
+			 * We don't need to initialize conn->prng_state here, because that
+			 * already happened in connectOptions2.
+			 */
+			for (int i = 1; i < conn->naddr; i++)
+			{
+				int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+				AddrInfo	temp = conn->addr[j];
+
+				if (j < i)		/* avoid fetching undefined data if j=i */
+					conn->addr[j] = conn->addr[i];
+				conn->addr[i] = temp;
+			}
+		}
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -4069,6 +4187,8 @@ freePGconn(PGconn *conn)
 	free(conn->outBuffer);
 	free(conn->rowBuf);
 	free(conn->target_session_attrs);
+	free(conn->load_balance_hosts);
+	free(conn->randomseed);
 	termPQExpBuffer(&conn->errorMessage);
 	termPQExpBuffer(&conn->workBuffer);
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 4d40e8a2fbb..0fabe969c70 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -26,7 +26,8 @@
 #include <netdb.h>
 #include <sys/socket.h>
 #include <time.h>
-#ifndef WIN32
+/* MinGW has sys/time.h, but MSVC doesn't */
+#ifndef _MSC_VER
 #include <sys/time.h>
 #endif
 
@@ -82,6 +83,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -242,6 +245,13 @@ typedef enum
 	SERVER_TYPE_PREFER_STANDBY_PASS2	/* second pass - behaves same as ANY */
 } PGTargetServerType;
 
+/* Target server type (decoded value of load_balance_hosts) */
+typedef enum
+{
+	LOAD_BALANCE_DISABLE = 0,	/* Use the existing host order (default) */
+	LOAD_BALANCE_RANDOM,		/* Read-write server */
+}			PGLoadBalanceType;
+
 /* Boolean value plus a not-known state, for GUCs we might have to fetch */
 typedef enum
 {
@@ -396,6 +406,8 @@ struct pg_conn
 	char	   *ssl_min_protocol_version;	/* minimum TLS protocol version */
 	char	   *ssl_max_protocol_version;	/* maximum TLS protocol version */
 	char	   *target_session_attrs;	/* desired session properties */
+	char	   *load_balance_hosts; /* load balance over hosts */
+	char	   *randomseed;		/* seed for randomization of load balancing */
 
 	/* Optional file to write trace info to */
 	FILE	   *Pfdebug;
@@ -459,6 +471,8 @@ struct pg_conn
 
 	/* Transient state needed while establishing connection */
 	PGTargetServerType target_server_type;	/* desired session properties */
+	PGLoadBalanceType load_balance_type;	/* desired load balancing
+											 * algorithm */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
 	int			naddr;			/* number of addresses returned by getaddrinfo */
@@ -479,6 +493,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index 573fd9b6ea4..edebb014362 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -116,6 +116,8 @@ tests += {
     'tests': [
       't/001_uri.pl',
       't/002_api.pl',
+      't/003_loadbalance_host_list.pl',
+      't/004_loadbalance_dns.pl',
     ],
     'env': {'with_ssl': get_option('ssl')},
   },
diff --git a/src/interfaces/libpq/t/003_loadbalance_host_list.pl b/src/interfaces/libpq/t/003_loadbalance_host_list.pl
new file mode 100644
index 00000000000..547b7d34fa4
--- /dev/null
+++ b/src/interfaces/libpq/t/003_loadbalance_host_list.pl
@@ -0,0 +1,76 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests load balancing across the list of different hosts in the host
+# parameter of the connection string.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $node1 = PostgreSQL::Test::Cluster->new('node1');
+my $node2 = PostgreSQL::Test::Cluster->new('node2', own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# Start the tests for load balancing method 1
+my $hostlist = $node1->host . ',' . $node2->host . ',' . $node3->host;
+my $portlist = $node1->port . ',' . $node2->port . ',' . $node3->port;
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 selects node 1 first",
+	sql => "SELECT 'connect1'",
+	log_like => [qr/statement: SELECT 'connect1'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 does not select node 2 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 does not select node 3 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 selects node 3 first",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 1 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node3->stop();
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does select node 1 second",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 second",
+	sql => "SELECT 'connect3'",
+	log_unlike => [qr/statement: SELECT 'connect3'/]);
+
+$node3->start();
+
+done_testing();
+
diff --git a/src/interfaces/libpq/t/004_loadbalance_dns.pl b/src/interfaces/libpq/t/004_loadbalance_dns.pl
new file mode 100644
index 00000000000..2512c41c466
--- /dev/null
+++ b/src/interfaces/libpq/t/004_loadbalance_dns.pl
@@ -0,0 +1,103 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests loadbalancing based on a DNS entry that contains multiple records
+# for different IPs. Since setting up a DNS server is more effort than we
+# consider reasonable to run this test, this situation is instead immitated by
+# using a hosts file where a single hostname maps to multiple different IP
+# addresses. This test requires the adminstrator to add the following lines to
+# the hosts file (if we detect that this hasn't happend we skip the test):
+#
+# 127.0.0.1 pg-loadbalancetest
+# 127.0.0.2 pg-loadbalancetest
+# 127.0.0.3 pg-loadbalancetest
+#
+# Windows or Linux are required to run this test because these OSes allow
+# binding to 127.0.0.2 and 127.0.0.3 addresess by default, but other OSes
+# don't. We need to bind to different IP addresses, so that we can use these
+# different IP addresses in the hosts file.
+#
+# The hosts file needs to be prepared before running this test. We don't do it
+# on the fly, because it requires root permissions to change the hosts file. In
+# CI we set up the previously mentioned rules in the hosts file, so that this
+# load balancing method is tested.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os;
+
+# Checks for the requirements for testing load balancing method 2
+if (!$can_bind_to_127_0_0_2) {
+	plan skip_all => "OS could not bind to 127.0.0.2"
+}
+
+my $hosts_path;
+if ($windows_os) {
+	$hosts_path = 'c:\Windows\System32\Drivers\etc\hosts';
+}
+else
+{
+	$hosts_path = '/etc/hosts';
+}
+
+my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path);
+
+if ($hosts_content !~ m/pg-loadbalancetest/) {
+	# Host file is not prepared for this test
+	plan skip_all => "hosts file was not prepared for DNS load balance test"
+}
+
+if ($ENV{PG_TEST_EXTRA} !~ /\bloadbalance\b/)
+{
+	plan skip_all => 'Potentially unsafe test loadbalance not enabled in PG_TEST_EXTRA';
+}
+
+$PostgreSQL::Test::Cluster::use_tcp = 1;
+$PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1';
+my $port = PostgreSQL::Test::Cluster::get_free_port();
+my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port);
+my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+$node2->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 selects node 2 first",
+	sql => "SELECT 'connect4'",
+	log_like => [qr/statement: SELECT 'connect4'/]);
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 1 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 3 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node2->stop();
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does select node 1 second",
+	sql => "SELECT 'connect5'",
+	log_like => [qr/statement: SELECT 'connect5'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 3 second",
+	sql => "SELECT 'connect5'",
+	log_unlike => [qr/statement: SELECT 'connect5'/]);
+
+done_testing();
-- 
2.34.1

From 38e4e78bd0e768d03f99d50605e1782b5fdafd66 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 30 Nov 2022 10:07:19 +0100
Subject: [PATCH v9 1/3] libpq: Run pgindent after a9e9a9f32b3

It seems that pgindent was not run after the error handling refactor in
commit a9e9a9f32b35edf129c88e8b929ef223f8511f59. This fixes that and
also addresses a few other things pgindent wanted to change in libpq.
---
 src/interfaces/libpq/fe-auth-scram.c     |   2 +-
 src/interfaces/libpq/fe-auth.c           |   8 +-
 src/interfaces/libpq/fe-connect.c        | 110 +++++++++++------------
 src/interfaces/libpq/fe-exec.c           |  16 ++--
 src/interfaces/libpq/fe-lobj.c           |  42 ++++-----
 src/interfaces/libpq/fe-misc.c           |  10 +--
 src/interfaces/libpq/fe-protocol3.c      |   2 +-
 src/interfaces/libpq/fe-secure-common.c  |   6 +-
 src/interfaces/libpq/fe-secure-gssapi.c  |  12 +--
 src/interfaces/libpq/fe-secure-openssl.c |  64 ++++++-------
 src/interfaces/libpq/fe-secure.c         |   8 +-
 src/interfaces/libpq/libpq-int.h         |   4 +-
 12 files changed, 142 insertions(+), 142 deletions(-)

diff --git a/src/interfaces/libpq/fe-auth-scram.c b/src/interfaces/libpq/fe-auth-scram.c
index 9c42ea4f819..12c3d0bc333 100644
--- a/src/interfaces/libpq/fe-auth-scram.c
+++ b/src/interfaces/libpq/fe-auth-scram.c
@@ -716,7 +716,7 @@ read_server_final_message(fe_scram_state *state, char *input)
 			return false;
 		}
 		libpq_append_conn_error(conn, "error received from server in SCRAM exchange: %s",
-						   errmsg);
+								errmsg);
 		return false;
 	}
 
diff --git a/src/interfaces/libpq/fe-auth.c b/src/interfaces/libpq/fe-auth.c
index 9afc6f19b9a..ab454e6cd02 100644
--- a/src/interfaces/libpq/fe-auth.c
+++ b/src/interfaces/libpq/fe-auth.c
@@ -73,7 +73,7 @@ pg_GSS_continue(PGconn *conn, int payloadlen)
 		if (!ginbuf.value)
 		{
 			libpq_append_conn_error(conn, "out of memory allocating GSSAPI buffer (%d)",
-							  payloadlen);
+									payloadlen);
 			return STATUS_ERROR;
 		}
 		if (pqGetnchar(ginbuf.value, payloadlen, conn))
@@ -223,7 +223,7 @@ pg_SSPI_continue(PGconn *conn, int payloadlen)
 		if (!inputbuf)
 		{
 			libpq_append_conn_error(conn, "out of memory allocating SSPI buffer (%d)",
-							  payloadlen);
+									payloadlen);
 			return STATUS_ERROR;
 		}
 		if (pqGetnchar(inputbuf, payloadlen, conn))
@@ -623,7 +623,7 @@ pg_SASL_continue(PGconn *conn, int payloadlen, bool final)
 	if (!challenge)
 	{
 		libpq_append_conn_error(conn, "out of memory allocating SASL buffer (%d)",
-						  payloadlen);
+								payloadlen);
 		return STATUS_ERROR;
 	}
 
@@ -1277,7 +1277,7 @@ PQencryptPasswordConn(PGconn *conn, const char *passwd, const char *user,
 	else
 	{
 		libpq_append_conn_error(conn, "unrecognized password encryption algorithm \"%s\"",
-						  algorithm);
+								algorithm);
 		return NULL;
 	}
 
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 8f80c35c894..97e47f05852 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -1079,7 +1079,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "could not match %d host names to %d hostaddr values",
-							   count_comma_separated_elems(conn->pghost), conn->nconnhost);
+									count_comma_separated_elems(conn->pghost), conn->nconnhost);
 			return false;
 		}
 	}
@@ -1159,7 +1159,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "could not match %d port numbers to %d hosts",
-							   count_comma_separated_elems(conn->pgport), conn->nconnhost);
+									count_comma_separated_elems(conn->pgport), conn->nconnhost);
 			return false;
 		}
 	}
@@ -1248,7 +1248,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "channel_binding", conn->channel_binding);
+									"channel_binding", conn->channel_binding);
 			return false;
 		}
 	}
@@ -1273,7 +1273,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "sslmode", conn->sslmode);
+									"sslmode", conn->sslmode);
 			return false;
 		}
 
@@ -1293,7 +1293,7 @@ connectOptions2(PGconn *conn)
 			case 'v':			/* "verify-ca" or "verify-full" */
 				conn->status = CONNECTION_BAD;
 				libpq_append_conn_error(conn, "sslmode value \"%s\" invalid when SSL support is not compiled in",
-								   conn->sslmode);
+										conn->sslmode);
 				return false;
 		}
 #endif
@@ -1313,16 +1313,16 @@ connectOptions2(PGconn *conn)
 	{
 		conn->status = CONNECTION_BAD;
 		libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-						   "ssl_min_protocol_version",
-						   conn->ssl_min_protocol_version);
+								"ssl_min_protocol_version",
+								conn->ssl_min_protocol_version);
 		return false;
 	}
 	if (!sslVerifyProtocolVersion(conn->ssl_max_protocol_version))
 	{
 		conn->status = CONNECTION_BAD;
 		libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-						   "ssl_max_protocol_version",
-						   conn->ssl_max_protocol_version);
+								"ssl_max_protocol_version",
+								conn->ssl_max_protocol_version);
 		return false;
 	}
 
@@ -1359,7 +1359,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "gssencmode value \"%s\" invalid when GSSAPI support is not compiled in",
-							   conn->gssencmode);
+									conn->gssencmode);
 			return false;
 		}
 #endif
@@ -1392,8 +1392,8 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "target_session_attrs",
-							   conn->target_session_attrs);
+									"target_session_attrs",
+									conn->target_session_attrs);
 			return false;
 		}
 	}
@@ -1609,7 +1609,7 @@ connectNoDelay(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "could not set socket to TCP no delay mode: %s",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1787,7 +1787,7 @@ parse_int_param(const char *value, int *result, PGconn *conn,
 
 error:
 	libpq_append_conn_error(conn, "invalid integer value \"%s\" for connection option \"%s\"",
-					   value, context);
+							value, context);
 	return false;
 }
 
@@ -1816,9 +1816,9 @@ setKeepalivesIdle(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   PG_TCP_KEEPALIVE_IDLE_STR,
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								PG_TCP_KEEPALIVE_IDLE_STR,
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1850,9 +1850,9 @@ setKeepalivesInterval(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_KEEPINTVL",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_KEEPINTVL",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1885,9 +1885,9 @@ setKeepalivesCount(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_KEEPCNT",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_KEEPCNT",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1949,8 +1949,8 @@ prepKeepalivesWin32(PGconn *conn)
 	if (!setKeepalivesWin32(conn->sock, idle, interval))
 	{
 		libpq_append_conn_error(conn, "%s(%s) failed: error code %d",
-						  "WSAIoctl", "SIO_KEEPALIVE_VALS",
-						  WSAGetLastError());
+								"WSAIoctl", "SIO_KEEPALIVE_VALS",
+								WSAGetLastError());
 		return 0;
 	}
 	return 1;
@@ -1983,9 +1983,9 @@ setTCPUserTimeout(PGconn *conn)
 		char		sebuf[256];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_USER_TIMEOUT",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_USER_TIMEOUT",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -2354,7 +2354,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
-									   ch->host, gai_strerror(ret));
+											ch->host, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2366,7 +2366,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
-									   ch->hostaddr, gai_strerror(ret));
+											ch->hostaddr, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2377,8 +2377,8 @@ keep_going:						/* We will come back to here until there is
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
 					libpq_append_conn_error(conn, "Unix-domain socket path \"%s\" is too long (maximum %d bytes)",
-									   portstr,
-									   (int) (UNIXSOCK_PATH_BUFLEN - 1));
+											portstr,
+											(int) (UNIXSOCK_PATH_BUFLEN - 1));
 					goto keep_going;
 				}
 
@@ -2391,7 +2391,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
-									   portstr, gai_strerror(ret));
+											portstr, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2513,7 +2513,7 @@ keep_going:						/* We will come back to here until there is
 						}
 						emitHostIdentityInfo(conn, host_addr);
 						libpq_append_conn_error(conn, "could not create socket: %s",
-										   SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2543,7 +2543,7 @@ keep_going:						/* We will come back to here until there is
 					if (!pg_set_noblock(conn->sock))
 					{
 						libpq_append_conn_error(conn, "could not set socket to nonblocking mode: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						conn->try_next_addr = true;
 						goto keep_going;
 					}
@@ -2552,7 +2552,7 @@ keep_going:						/* We will come back to here until there is
 					if (fcntl(conn->sock, F_SETFD, FD_CLOEXEC) == -1)
 					{
 						libpq_append_conn_error(conn, "could not set socket to close-on-exec mode: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						conn->try_next_addr = true;
 						goto keep_going;
 					}
@@ -2581,9 +2581,9 @@ keep_going:						/* We will come back to here until there is
 											(char *) &on, sizeof(on)) < 0)
 						{
 							libpq_append_conn_error(conn, "%s(%s) failed: %s",
-											   "setsockopt",
-											   "SO_KEEPALIVE",
-											   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+													"setsockopt",
+													"SO_KEEPALIVE",
+													SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 							err = 1;
 						}
 						else if (!setKeepalivesIdle(conn)
@@ -2708,7 +2708,7 @@ keep_going:						/* We will come back to here until there is
 							   (char *) &optval, &optlen) == -1)
 				{
 					libpq_append_conn_error(conn, "could not get socket error status: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					goto error_return;
 				}
 				else if (optval != 0)
@@ -2735,7 +2735,7 @@ keep_going:						/* We will come back to here until there is
 								&conn->laddr.salen) < 0)
 				{
 					libpq_append_conn_error(conn, "could not get client address from socket: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					goto error_return;
 				}
 
@@ -2775,7 +2775,7 @@ keep_going:						/* We will come back to here until there is
 							libpq_append_conn_error(conn, "requirepeer parameter is not supported on this platform");
 						else
 							libpq_append_conn_error(conn, "could not get peer credentials: %s",
-											   strerror_r(errno, sebuf, sizeof(sebuf)));
+													strerror_r(errno, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2788,7 +2788,7 @@ keep_going:						/* We will come back to here until there is
 					if (strcmp(remote_username, conn->requirepeer) != 0)
 					{
 						libpq_append_conn_error(conn, "requirepeer specifies \"%s\", but actual peer user name is \"%s\"",
-										   conn->requirepeer, remote_username);
+												conn->requirepeer, remote_username);
 						free(remote_username);
 						goto error_return;
 					}
@@ -2829,7 +2829,7 @@ keep_going:						/* We will come back to here until there is
 					if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
 					{
 						libpq_append_conn_error(conn, "could not send GSSAPI negotiation packet: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2840,7 +2840,7 @@ keep_going:						/* We will come back to here until there is
 				else if (!conn->gctx && conn->gssencmode[0] == 'r')
 				{
 					libpq_append_conn_error(conn,
-									   "GSSAPI encryption required but was impossible (possibly no credential cache, no server support, or using a local socket)");
+											"GSSAPI encryption required but was impossible (possibly no credential cache, no server support, or using a local socket)");
 					goto error_return;
 				}
 #endif
@@ -2882,7 +2882,7 @@ keep_going:						/* We will come back to here until there is
 					if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
 					{
 						libpq_append_conn_error(conn, "could not send SSL negotiation packet: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 					/* Ok, wait for response */
@@ -2911,7 +2911,7 @@ keep_going:						/* We will come back to here until there is
 				if (pqPacketSend(conn, 0, startpacket, packetlen) != STATUS_OK)
 				{
 					libpq_append_conn_error(conn, "could not send startup packet: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					free(startpacket);
 					goto error_return;
 				}
@@ -3012,7 +3012,7 @@ keep_going:						/* We will come back to here until there is
 					else
 					{
 						libpq_append_conn_error(conn, "received invalid response to SSL negotiation: %c",
-										   SSLok);
+												SSLok);
 						goto error_return;
 					}
 				}
@@ -3123,7 +3123,7 @@ keep_going:						/* We will come back to here until there is
 					else if (gss_ok != 'G')
 					{
 						libpq_append_conn_error(conn, "received invalid response to GSSAPI negotiation: %c",
-										   gss_ok);
+												gss_ok);
 						goto error_return;
 					}
 				}
@@ -3201,7 +3201,7 @@ keep_going:						/* We will come back to here until there is
 				if (!(beresp == 'R' || beresp == 'v' || beresp == 'E'))
 				{
 					libpq_append_conn_error(conn, "expected authentication request from server, but received %c",
-									   beresp);
+											beresp);
 					goto error_return;
 				}
 
@@ -3732,7 +3732,7 @@ keep_going:						/* We will come back to here until there is
 
 				/* Append error report to conn->errorMessage. */
 				libpq_append_conn_error(conn, "\"%s\" failed",
-								  "SHOW transaction_read_only");
+										"SHOW transaction_read_only");
 
 				/* Close connection politely. */
 				conn->status = CONNECTION_OK;
@@ -3782,7 +3782,7 @@ keep_going:						/* We will come back to here until there is
 
 				/* Append error report to conn->errorMessage. */
 				libpq_append_conn_error(conn, "\"%s\" failed",
-								  "SELECT pg_is_in_recovery()");
+										"SELECT pg_is_in_recovery()");
 
 				/* Close connection politely. */
 				conn->status = CONNECTION_OK;
@@ -3795,8 +3795,8 @@ keep_going:						/* We will come back to here until there is
 
 		default:
 			libpq_append_conn_error(conn,
-							   "invalid connection state %d, probably indicative of memory corruption",
-							  conn->status);
+									"invalid connection state %d, probably indicative of memory corruption",
+									conn->status);
 			goto error_return;
 	}
 
@@ -7175,7 +7175,7 @@ pgpassfileWarning(PGconn *conn)
 
 		if (sqlstate && strcmp(sqlstate, ERRCODE_INVALID_PASSWORD) == 0)
 			libpq_append_conn_error(conn, "password retrieved from file \"%s\"",
-							  conn->pgpassfile);
+									conn->pgpassfile);
 	}
 }
 
diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index ec62550e385..0c2dae6ed9e 100644
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -1444,7 +1444,7 @@ PQsendQueryInternal(PGconn *conn, const char *query, bool newQuery)
 	if (conn->pipelineStatus != PQ_PIPELINE_OFF)
 	{
 		libpq_append_conn_error(conn, "%s not allowed in pipeline mode",
-						  "PQsendQuery");
+								"PQsendQuery");
 		return 0;
 	}
 
@@ -1512,7 +1512,7 @@ PQsendQueryParams(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1558,7 +1558,7 @@ PQsendPrepare(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1652,7 +1652,7 @@ PQsendQueryPrepared(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -2099,10 +2099,9 @@ PQgetResult(PGconn *conn)
 
 			/*
 			 * We're about to return the NULL that terminates the round of
-			 * results from the current query; prepare to send the results
-			 * of the next query, if any, when we're called next.  If there's
-			 * no next element in the command queue, this gets us in IDLE
-			 * state.
+			 * results from the current query; prepare to send the results of
+			 * the next query, if any, when we're called next.  If there's no
+			 * next element in the command queue, this gets us in IDLE state.
 			 */
 			pqPipelineProcessQueue(conn);
 			res = NULL;			/* query is complete */
@@ -3047,6 +3046,7 @@ pqPipelineProcessQueue(PGconn *conn)
 			return;
 
 		case PGASYNC_IDLE:
+
 			/*
 			 * If we're in IDLE mode and there's some command in the queue,
 			 * get us into PIPELINE_IDLE mode and process normally.  Otherwise
diff --git a/src/interfaces/libpq/fe-lobj.c b/src/interfaces/libpq/fe-lobj.c
index 4cb6a468597..206266fd043 100644
--- a/src/interfaces/libpq/fe-lobj.c
+++ b/src/interfaces/libpq/fe-lobj.c
@@ -142,7 +142,7 @@ lo_truncate(PGconn *conn, int fd, size_t len)
 	if (conn->lobjfuncs->fn_lo_truncate == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate");
+								"lo_truncate");
 		return -1;
 	}
 
@@ -205,7 +205,7 @@ lo_truncate64(PGconn *conn, int fd, pg_int64 len)
 	if (conn->lobjfuncs->fn_lo_truncate64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate64");
+								"lo_truncate64");
 		return -1;
 	}
 
@@ -395,7 +395,7 @@ lo_lseek64(PGconn *conn, int fd, pg_int64 offset, int whence)
 	if (conn->lobjfuncs->fn_lo_lseek64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek64");
+								"lo_lseek64");
 		return -1;
 	}
 
@@ -485,7 +485,7 @@ lo_create(PGconn *conn, Oid lobjId)
 	if (conn->lobjfuncs->fn_lo_create == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_create");
+								"lo_create");
 		return InvalidOid;
 	}
 
@@ -558,7 +558,7 @@ lo_tell64(PGconn *conn, int fd)
 	if (conn->lobjfuncs->fn_lo_tell64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell64");
+								"lo_tell64");
 		return -1;
 	}
 
@@ -667,7 +667,7 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 	if (fd < 0)
 	{							/* error */
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -723,8 +723,8 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not read from file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -778,8 +778,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -799,8 +799,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 			/* deliberately overwrite any error from lo_close */
 			pqClearConnErrorState(conn);
 			libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-							  filename,
-							  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+									filename,
+									strerror_r(save_errno, sebuf, sizeof(sebuf)));
 			return -1;
 		}
 	}
@@ -822,7 +822,7 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 	if (close(fd) != 0 && result >= 0)
 	{
 		libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		result = -1;
 	}
 
@@ -954,56 +954,56 @@ lo_initialize(PGconn *conn)
 	if (lobjfuncs->fn_lo_open == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_open");
+								"lo_open");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_close == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_close");
+								"lo_close");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_creat == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_creat");
+								"lo_creat");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_unlink == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_unlink");
+								"lo_unlink");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_lseek == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek");
+								"lo_lseek");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_tell == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell");
+								"lo_tell");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_read == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "loread");
+								"loread");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_write == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lowrite");
+								"lowrite");
 		free(lobjfuncs);
 		return -1;
 	}
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 3653a1a8a62..660cdec93c9 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -749,8 +749,8 @@ retry4:
 	 */
 definitelyEOF:
 	libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-					   "\tThis probably means the server terminated abnormally\n"
-					   "\tbefore or while processing the request.");
+							"\tThis probably means the server terminated abnormally\n"
+							"\tbefore or while processing the request.");
 
 	/* Come here if lower-level code already set a suitable errorMessage */
 definitelyFailed:
@@ -1067,7 +1067,7 @@ pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s() failed: %s", "select",
-						  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 	}
 
 	return result;
@@ -1280,7 +1280,7 @@ libpq_ngettext(const char *msgid, const char *msgid_plural, unsigned long n)
  * newline.
  */
 void
-libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
+libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
@@ -1309,7 +1309,7 @@ libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
  * format should not end with a newline.
  */
 void
-libpq_append_conn_error(PGconn *conn, const char *fmt, ...)
+libpq_append_conn_error(PGconn *conn, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index 8ab6a884165..b79d74f7489 100644
--- a/src/interfaces/libpq/fe-protocol3.c
+++ b/src/interfaces/libpq/fe-protocol3.c
@@ -466,7 +466,7 @@ static void
 handleSyncLoss(PGconn *conn, char id, int msgLength)
 {
 	libpq_append_conn_error(conn, "lost synchronization with server: got message type \"%c\", length %d",
-					  id, msgLength);
+							id, msgLength);
 	/* build an error result holding the error message */
 	pqSaveErrorResult(conn);
 	conn->asyncStatus = PGASYNC_READY;	/* drop out of PQgetResult wait loop */
diff --git a/src/interfaces/libpq/fe-secure-common.c b/src/interfaces/libpq/fe-secure-common.c
index de115b37649..3ecc7bf6159 100644
--- a/src/interfaces/libpq/fe-secure-common.c
+++ b/src/interfaces/libpq/fe-secure-common.c
@@ -226,7 +226,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 		 * wrong given the subject matter.
 		 */
 		libpq_append_conn_error(conn, "certificate contains IP address with invalid length %zu",
-						  iplen);
+								iplen);
 		return -1;
 	}
 
@@ -235,7 +235,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 	if (!addrstr)
 	{
 		libpq_append_conn_error(conn, "could not convert certificate's IP address to string: %s",
-						  strerror_r(errno, sebuf, sizeof(sebuf)));
+								strerror_r(errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -292,7 +292,7 @@ pq_verify_peer_name_matches_certificate(PGconn *conn)
 		else if (names_examined == 1)
 		{
 			libpq_append_conn_error(conn, "server certificate for \"%s\" does not match host name \"%s\"",
-							  first_name, host);
+									first_name, host);
 		}
 		else
 		{
diff --git a/src/interfaces/libpq/fe-secure-gssapi.c b/src/interfaces/libpq/fe-secure-gssapi.c
index 038e847b7e9..0af4de941af 100644
--- a/src/interfaces/libpq/fe-secure-gssapi.c
+++ b/src/interfaces/libpq/fe-secure-gssapi.c
@@ -213,8 +213,8 @@ pg_GSS_write(PGconn *conn, const void *ptr, size_t len)
 		if (output.length > PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "client tried to send oversize GSSAPI packet (%zu > %zu)",
-							  (size_t) output.length,
-							  PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
+									(size_t) output.length,
+									PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			goto cleanup;
 		}
@@ -349,8 +349,8 @@ pg_GSS_read(PGconn *conn, void *ptr, size_t len)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			return -1;
 		}
@@ -590,8 +590,8 @@ pqsecure_open_gss(PGconn *conn)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			return PGRES_POLLING_FAILED;
 		}
 
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index 6a4431ddfe9..e6da377fb9d 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -213,12 +213,12 @@ rloop:
 				if (result_errno == EPIPE ||
 					result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -313,12 +313,12 @@ pgtls_write(PGconn *conn, const void *ptr, size_t len)
 				result_errno = SOCK_ERRNO;
 				if (result_errno == EPIPE || result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -415,7 +415,7 @@ pgtls_get_peer_certificate_hash(PGconn *conn, size_t *len)
 			if (algo_type == NULL)
 			{
 				libpq_append_conn_error(conn, "could not find digest for NID %s",
-								  OBJ_nid2sn(algo_nid));
+										OBJ_nid2sn(algo_nid));
 				return NULL;
 			}
 			break;
@@ -967,7 +967,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_min_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for minimum SSL protocol version",
-							  conn->ssl_min_protocol_version);
+									conn->ssl_min_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -993,7 +993,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_max_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for maximum SSL protocol version",
-							  conn->ssl_max_protocol_version);
+									conn->ssl_max_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1037,7 +1037,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read root certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1089,10 +1089,10 @@ initialize_SSL(PGconn *conn)
 			 */
 			if (fnbuf[0] == '\0')
 				libpq_append_conn_error(conn, "could not get home directory to locate root certificate file\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.");
+										"Either provide the file or change sslmode to disable server certificate verification.");
 			else
 				libpq_append_conn_error(conn, "root certificate file \"%s\" does not exist\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
+										"Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1122,7 +1122,7 @@ initialize_SSL(PGconn *conn)
 		if (errno != ENOENT && errno != ENOTDIR)
 		{
 			libpq_append_conn_error(conn, "could not open certificate file \"%s\": %s",
-							  fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
+									fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1140,7 +1140,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1239,7 +1239,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				free(engine_str);
 				return -1;
@@ -1250,7 +1250,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not initialize SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				ENGINE_free(conn->engine);
 				conn->engine = NULL;
@@ -1265,7 +1265,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not read private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1278,7 +1278,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1315,10 +1315,10 @@ initialize_SSL(PGconn *conn)
 		{
 			if (errno == ENOENT)
 				libpq_append_conn_error(conn, "certificate present, but not private key file \"%s\"",
-								  fnbuf);
+										fnbuf);
 			else
 				libpq_append_conn_error(conn, "could not stat private key file \"%s\": %m",
-								  fnbuf);
+										fnbuf);
 			return -1;
 		}
 
@@ -1326,7 +1326,7 @@ initialize_SSL(PGconn *conn)
 		if (!S_ISREG(buf.st_mode))
 		{
 			libpq_append_conn_error(conn, "private key file \"%s\" is not a regular file",
-							  fnbuf);
+									fnbuf);
 			return -1;
 		}
 
@@ -1383,7 +1383,7 @@ initialize_SSL(PGconn *conn)
 			if (SSL_use_PrivateKey_file(conn->ssl, fnbuf, SSL_FILETYPE_ASN1) != 1)
 			{
 				libpq_append_conn_error(conn, "could not load private key file \"%s\": %s",
-								  fnbuf, err);
+										fnbuf, err);
 				SSLerrfree(err);
 				return -1;
 			}
@@ -1399,7 +1399,7 @@ initialize_SSL(PGconn *conn)
 		char	   *err = SSLerrmessage(ERR_get_error());
 
 		libpq_append_conn_error(conn, "certificate does not match private key file \"%s\": %s",
-						  fnbuf, err);
+								fnbuf, err);
 		SSLerrfree(err);
 		return -1;
 	}
@@ -1452,7 +1452,7 @@ open_client_SSL(PGconn *conn)
 
 					if (r == -1)
 						libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-										  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					else
 						libpq_append_conn_error(conn, "SSL SYSCALL error: EOF detected");
 					pgtls_close(conn);
@@ -1494,12 +1494,12 @@ open_client_SSL(PGconn *conn)
 						case SSL_R_VERSION_TOO_LOW:
 #endif
 							libpq_append_conn_error(conn, "This may indicate that the server does not support any SSL protocol version between %s and %s.",
-											  conn->ssl_min_protocol_version ?
-											  conn->ssl_min_protocol_version :
-											  MIN_OPENSSL_TLS_VERSION,
-											  conn->ssl_max_protocol_version ?
-											  conn->ssl_max_protocol_version :
-											  MAX_OPENSSL_TLS_VERSION);
+													conn->ssl_min_protocol_version ?
+													conn->ssl_min_protocol_version :
+													MIN_OPENSSL_TLS_VERSION,
+													conn->ssl_max_protocol_version ?
+													conn->ssl_max_protocol_version :
+													MAX_OPENSSL_TLS_VERSION);
 							break;
 						default:
 							break;
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index 66e401bf3d9..8069e381424 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -255,14 +255,14 @@ pqsecure_raw_read(PGconn *conn, void *ptr, size_t len)
 			case EPIPE:
 			case ECONNRESET:
 				libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-								   "\tThis probably means the server terminated abnormally\n"
-								   "\tbefore or while processing the request.");
+										"\tThis probably means the server terminated abnormally\n"
+										"\tbefore or while processing the request.");
 				break;
 
 			default:
 				libpq_append_conn_error(conn, "could not receive data from server: %s",
-								  SOCK_STRERROR(result_errno,
-												sebuf, sizeof(sebuf)));
+										SOCK_STRERROR(result_errno,
+													  sebuf, sizeof(sebuf)));
 				break;
 		}
 	}
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index d7ec5ed4293..85289980a11 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -888,8 +888,8 @@ extern char *libpq_ngettext(const char *msgid, const char *msgid_plural, unsigne
  */
 #undef _
 
-extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...) pg_attribute_printf(2, 3);
-extern void libpq_append_conn_error(PGconn *conn, const char *fmt, ...) pg_attribute_printf(2, 3);
+extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...) pg_attribute_printf(2, 3);
+extern void libpq_append_conn_error(PGconn *conn, const char *fmt,...) pg_attribute_printf(2, 3);
 
 /*
  * These macros are needed to let error-handling code be portable between
-- 
2.34.1

From 6913581f0e2fb94e99e006a6d2c4a402ddb7dc0d Mon Sep 17 00:00:00 2001
From: Jelte Fennema <github-tech@jeltef.nl>
Date: Mon, 12 Sep 2022 09:44:06 +0200
Subject: [PATCH v10 3/4] Support load balancing in libpq

This adds support for load balancing to libpq using the newly added
load_balance_hosts parameter. When setting the load_balance_hosts
parameter to random, hosts and addresses will be connected to in a
random order. This then results in load balancing across these
hosts/addresses if multiple clients do this at the same time.

This patch implements two levels of random load balancing:
1. The given hosts are randomly shuffled, before resolving them
    one-by-one.
2. Once a host its addresses get resolved, those addresses are shuffled,
    before trying to connect to them one-by-one.
---
 .cirrus.yml                                   |  16 ++-
 doc/src/sgml/libpq.sgml                       |  69 ++++++++++
 doc/src/sgml/regress.sgml                     |  11 +-
 src/interfaces/libpq/fe-connect.c             | 118 ++++++++++++++++++
 src/interfaces/libpq/libpq-int.h              |  18 ++-
 src/interfaces/libpq/meson.build              |   2 +
 .../libpq/t/003_loadbalance_host_list.pl      |  76 +++++++++++
 src/interfaces/libpq/t/004_loadbalance_dns.pl | 103 +++++++++++++++
 8 files changed, 410 insertions(+), 3 deletions(-)
 create mode 100644 src/interfaces/libpq/t/003_loadbalance_host_list.pl
 create mode 100644 src/interfaces/libpq/t/004_loadbalance_dns.pl

diff --git a/.cirrus.yml b/.cirrus.yml
index f2129787529..51f810a4031 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -25,7 +25,7 @@ env:
   MTEST_ARGS: --print-errorlogs --no-rebuild -C build
   PGCTLTIMEOUT: 120 # avoids spurious failures during parallel tests
   TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
-  PG_TEST_EXTRA: kerberos ldap ssl
+  PG_TEST_EXTRA: kerberos ldap ssl loadbalance
 
 
 # What files to preserve in case tests fail
@@ -314,6 +314,14 @@ task:
     mkdir -m 770 /tmp/cores
     chown root:postgres /tmp/cores
     sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core'
+
+  setup_hosts_file_script: |
+    cat >> /etc/hosts <<-EOF
+      127.0.0.1 pg-loadbalancetest
+      127.0.0.2 pg-loadbalancetest
+      127.0.0.3 pg-loadbalancetest
+    EOF
+
   setup_additional_packages_script: |
     #apt-get update
     #DEBIAN_FRONTEND=noninteractive apt-get -y install ...
@@ -565,6 +573,12 @@ task:
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
+  setup_hosts_file_script: |
+    echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    type c:\Windows\System32\Drivers\etc\hosts
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 3ccd8ff9421..ee5869c9274 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1964,6 +1964,75 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="libpq-connect-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls the order in which the client tries to connect to the available
+        hosts and addresses. It's typically used in combination with multiple
+        host names or a DNS record that returns multiple IPs. This parameter be
+        used in combination with <xref linkend="libpq-connect-target-session-attrs"/>
+        to, for example, load balance over stanby servers only. Once successfully
+        connected, subsequent queries on the returned connection will all be
+        sent to the same server. There are currently two modes:
+        <variablelist>
+         <varlistentry>
+          <term><literal>disable</literal> (default)</term>
+          <listitem>
+           <para>
+            Hosts are tried in the order in which they are provided and
+            addresses are tried in the order they are received from DNS or a
+            hosts file.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>random</literal></term>
+          <listitem>
+           <para>
+            The provided hosts and the addresses that they resolve to are
+            tried in random order. This value is mostly useful when opening
+            multiple connections at the same time, possibly from different
+            machines. This way connections can be load balanced across multiple
+            Postgres servers.
+           </para>
+           <para>
+            This algorithm uses two levels of random choices: First the hosts
+            will be resolved in random order. Then before resolving the next
+            host, all resolved addresses for the current host will be tried in
+            random order. This behaviour can lead to non-uniform address
+            selection in certain cases, for instance when some hosts resolve to
+            more addresses than others. So if you want uniform load balancing,
+            this is something to keep in mind. However, non-uniform load
+            balancing also can be used to your advantage, e.g. by providing the
+            hostname of a larger server multiple times in the host string so it
+            gets more connections.
+           </para>
+           <para>
+            When using this value it's recommended to also configure a reasonable
+            value for <xref linkend="libpq-connect-connect-timeout"/>. Because then,
+            if one of the nodes that are used for load balancing is not responding,
+            a new node will be tried.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-random-seed" xreflabel="random_seed">
+      <term><literal>random_seed</literal></term>
+      <listitem>
+       <para>
+        Sets the random seed that is used by <xref linkend="libpq-connect-load-balance-hosts"/>
+        to randomize the host order. This option is mostly useful when running
+        tests that require a stable random order.
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
    </para>
   </sect2>
diff --git a/doc/src/sgml/regress.sgml b/doc/src/sgml/regress.sgml
index a08c7a78af8..026ac05c755 100644
--- a/doc/src/sgml/regress.sgml
+++ b/doc/src/sgml/regress.sgml
@@ -256,7 +256,7 @@ make check-world -j8 >/dev/null
    <varname>PG_TEST_EXTRA</varname> to a whitespace-separated list, for
    example:
 <programlisting>
-make check-world PG_TEST_EXTRA='kerberos ldap ssl'
+make check-world PG_TEST_EXTRA='kerberos ldap ssl loadbalance'
 </programlisting>
    The following values are currently supported:
    <variablelist>
@@ -290,6 +290,15 @@ make check-world PG_TEST_EXTRA='kerberos ldap ssl'
      </listitem>
     </varlistentry>
 
+    <varlistentry>
+     <term><literal>loadbalance</literal></term>
+     <listitem>
+      <para>
+       Runs the test <filename>src/interfaces/libpq/t/004_loadbalance_dns.pl</filename>.  This opens TCP/IP listen sockets.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry>
      <term><literal>wal_consistency_checking</literal></term>
      <listitem>
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 41deeee9a63..b2fb47272a3 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -123,6 +123,7 @@ static int	ldapServiceLookup(const char *purl, PQconninfoOption *options,
 #define DefaultChannelBinding	"disable"
 #endif
 #define DefaultTargetSessionAttrs	"any"
+#define DefaultLoadBalanceHosts	"disable"
 #ifdef USE_SSL
 #define DefaultSSLMode "prefer"
 #else
@@ -341,6 +342,15 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Target-Session-Attrs", "", 15, /* sizeof("prefer-standby") = 15 */
 	offsetof(struct pg_conn, target_session_attrs)},
 
+	{"load_balance_hosts", "PGLOADBALANCEHOSTS",
+		DefaultLoadBalanceHosts, NULL,
+		"Load-Balance-Hosts", "", 8,	/* sizeof("disable") = 8 */
+	offsetof(struct pg_conn, load_balance_hosts)},
+
+	{"random_seed", NULL, NULL, NULL,
+		"Random-Seed", "", 10,	/* strlen(INT32_MAX) == 10 */
+	offsetof(struct pg_conn, randomseed)},
+
 	/* Terminating entry --- MUST BE LAST */
 	{NULL, NULL, NULL, NULL,
 	NULL, NULL, 0}
@@ -425,6 +435,8 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static bool parse_int_param(const char *value, int *result, PGconn *conn,
+							const char *context);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1008,6 +1020,40 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on timestamp and PID.
+ */
+static bool
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(conn->randomseed))
+	{
+		int			rseed;
+
+		if (!parse_int_param(conn->randomseed, &rseed, conn, "random_seed"))
+			return false;
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	else if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		struct timeval tval = {0};
+
+		gettimeofday(&tval, NULL);
+
+		rseed = ((uint64) conn) ^
+			((uint64) getpid()) ^
+			((uint64) tval.tv_usec) ^
+			((uint64) tval.tv_sec);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	return true;
+}
+
 /*
  *		connectOptions2
  *
@@ -1401,6 +1447,50 @@ connectOptions2(PGconn *conn)
 	else
 		conn->target_server_type = SERVER_TYPE_ANY;
 
+	/*
+	 * validate load_balance_hosts option, and set load_balance_type
+	 */
+	if (conn->load_balance_hosts)
+	{
+		if (strcmp(conn->load_balance_hosts, "disable") == 0)
+			conn->load_balance_type = LOAD_BALANCE_DISABLE;
+		else if (strcmp(conn->load_balance_hosts, "random") == 0)
+			conn->load_balance_type = LOAD_BALANCE_RANDOM;
+		else
+		{
+			conn->status = CONNECTION_BAD;
+			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
+									"load_balance_hosts",
+									conn->load_balance_hosts);
+			return false;
+		}
+	}
+	else
+		conn->load_balance_type = LOAD_BALANCE_DISABLE;
+
+	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+	{
+		if (!libpq_prng_init(conn))
+			return false;
+
+		/*
+		 * This is the "inside-out" variant of the Fisher-Yates shuffle
+		 * algorithm. Notionally, we append each new value to the array and
+		 * then swap it with a randomly-chosen array element (possibly
+		 * including itself, else we fail to generate permutations with the
+		 * last integer last).  The swap step can be optimized by combining it
+		 * with the insertion.
+		 */
+		for (i = 1; i < conn->nconnhost; i++)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
 	/*
 	 * Resolve special "auto" client_encoding from the locale
 	 */
@@ -2407,6 +2497,32 @@ keep_going:						/* We will come back to here until there is
 		}
 		pg_freeaddrinfo_all(hint.ai_family, addrlist);
 
+		/*
+		 * If random load balancing is enabled we shuffle the addresses.
+		 */
+		if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+		{
+			/*
+			 * This is the "inside-out" variant of the Fisher-Yates shuffle
+			 * algorithm. Notionally, we append each new value to the array
+			 * and then swap it with a randomly-chosen array element (possibly
+			 * including itself, else we fail to generate permutations with
+			 * the last integer last).  The swap step can be optimized by
+			 * combining it with the insertion.
+			 *
+			 * We don't need to initialize conn->prng_state here, because that
+			 * already happened in connectOptions2.
+			 */
+			for (int i = 1; i < conn->naddr; i++)
+			{
+				int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+				AddrInfo	temp = conn->addr[j];
+
+				conn->addr[j] = conn->addr[i];
+				conn->addr[i] = temp;
+			}
+		}
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -4069,6 +4185,8 @@ freePGconn(PGconn *conn)
 	free(conn->outBuffer);
 	free(conn->rowBuf);
 	free(conn->target_session_attrs);
+	free(conn->load_balance_hosts);
+	free(conn->randomseed);
 	termPQExpBuffer(&conn->errorMessage);
 	termPQExpBuffer(&conn->workBuffer);
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 4d40e8a2fbb..0fabe969c70 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -26,7 +26,8 @@
 #include <netdb.h>
 #include <sys/socket.h>
 #include <time.h>
-#ifndef WIN32
+/* MinGW has sys/time.h, but MSVC doesn't */
+#ifndef _MSC_VER
 #include <sys/time.h>
 #endif
 
@@ -82,6 +83,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -242,6 +245,13 @@ typedef enum
 	SERVER_TYPE_PREFER_STANDBY_PASS2	/* second pass - behaves same as ANY */
 } PGTargetServerType;
 
+/* Target server type (decoded value of load_balance_hosts) */
+typedef enum
+{
+	LOAD_BALANCE_DISABLE = 0,	/* Use the existing host order (default) */
+	LOAD_BALANCE_RANDOM,		/* Read-write server */
+}			PGLoadBalanceType;
+
 /* Boolean value plus a not-known state, for GUCs we might have to fetch */
 typedef enum
 {
@@ -396,6 +406,8 @@ struct pg_conn
 	char	   *ssl_min_protocol_version;	/* minimum TLS protocol version */
 	char	   *ssl_max_protocol_version;	/* maximum TLS protocol version */
 	char	   *target_session_attrs;	/* desired session properties */
+	char	   *load_balance_hosts; /* load balance over hosts */
+	char	   *randomseed;		/* seed for randomization of load balancing */
 
 	/* Optional file to write trace info to */
 	FILE	   *Pfdebug;
@@ -459,6 +471,8 @@ struct pg_conn
 
 	/* Transient state needed while establishing connection */
 	PGTargetServerType target_server_type;	/* desired session properties */
+	PGLoadBalanceType load_balance_type;	/* desired load balancing
+											 * algorithm */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
 	int			naddr;			/* number of addresses returned by getaddrinfo */
@@ -479,6 +493,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index 573fd9b6ea4..edebb014362 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -116,6 +116,8 @@ tests += {
     'tests': [
       't/001_uri.pl',
       't/002_api.pl',
+      't/003_loadbalance_host_list.pl',
+      't/004_loadbalance_dns.pl',
     ],
     'env': {'with_ssl': get_option('ssl')},
   },
diff --git a/src/interfaces/libpq/t/003_loadbalance_host_list.pl b/src/interfaces/libpq/t/003_loadbalance_host_list.pl
new file mode 100644
index 00000000000..547b7d34fa4
--- /dev/null
+++ b/src/interfaces/libpq/t/003_loadbalance_host_list.pl
@@ -0,0 +1,76 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests load balancing across the list of different hosts in the host
+# parameter of the connection string.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $node1 = PostgreSQL::Test::Cluster->new('node1');
+my $node2 = PostgreSQL::Test::Cluster->new('node2', own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# Start the tests for load balancing method 1
+my $hostlist = $node1->host . ',' . $node2->host . ',' . $node3->host;
+my $portlist = $node1->port . ',' . $node2->port . ',' . $node3->port;
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 selects node 1 first",
+	sql => "SELECT 'connect1'",
+	log_like => [qr/statement: SELECT 'connect1'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 does not select node 2 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 does not select node 3 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 selects node 3 first",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 1 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node3->stop();
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does select node 1 second",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 second",
+	sql => "SELECT 'connect3'",
+	log_unlike => [qr/statement: SELECT 'connect3'/]);
+
+$node3->start();
+
+done_testing();
+
diff --git a/src/interfaces/libpq/t/004_loadbalance_dns.pl b/src/interfaces/libpq/t/004_loadbalance_dns.pl
new file mode 100644
index 00000000000..2512c41c466
--- /dev/null
+++ b/src/interfaces/libpq/t/004_loadbalance_dns.pl
@@ -0,0 +1,103 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests loadbalancing based on a DNS entry that contains multiple records
+# for different IPs. Since setting up a DNS server is more effort than we
+# consider reasonable to run this test, this situation is instead immitated by
+# using a hosts file where a single hostname maps to multiple different IP
+# addresses. This test requires the adminstrator to add the following lines to
+# the hosts file (if we detect that this hasn't happend we skip the test):
+#
+# 127.0.0.1 pg-loadbalancetest
+# 127.0.0.2 pg-loadbalancetest
+# 127.0.0.3 pg-loadbalancetest
+#
+# Windows or Linux are required to run this test because these OSes allow
+# binding to 127.0.0.2 and 127.0.0.3 addresess by default, but other OSes
+# don't. We need to bind to different IP addresses, so that we can use these
+# different IP addresses in the hosts file.
+#
+# The hosts file needs to be prepared before running this test. We don't do it
+# on the fly, because it requires root permissions to change the hosts file. In
+# CI we set up the previously mentioned rules in the hosts file, so that this
+# load balancing method is tested.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os;
+
+# Checks for the requirements for testing load balancing method 2
+if (!$can_bind_to_127_0_0_2) {
+	plan skip_all => "OS could not bind to 127.0.0.2"
+}
+
+my $hosts_path;
+if ($windows_os) {
+	$hosts_path = 'c:\Windows\System32\Drivers\etc\hosts';
+}
+else
+{
+	$hosts_path = '/etc/hosts';
+}
+
+my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path);
+
+if ($hosts_content !~ m/pg-loadbalancetest/) {
+	# Host file is not prepared for this test
+	plan skip_all => "hosts file was not prepared for DNS load balance test"
+}
+
+if ($ENV{PG_TEST_EXTRA} !~ /\bloadbalance\b/)
+{
+	plan skip_all => 'Potentially unsafe test loadbalance not enabled in PG_TEST_EXTRA';
+}
+
+$PostgreSQL::Test::Cluster::use_tcp = 1;
+$PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1';
+my $port = PostgreSQL::Test::Cluster::get_free_port();
+my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port);
+my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+$node2->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 selects node 2 first",
+	sql => "SELECT 'connect4'",
+	log_like => [qr/statement: SELECT 'connect4'/]);
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 1 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 3 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node2->stop();
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does select node 1 second",
+	sql => "SELECT 'connect5'",
+	log_like => [qr/statement: SELECT 'connect5'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 3 second",
+	sql => "SELECT 'connect5'",
+	log_unlike => [qr/statement: SELECT 'connect5'/]);
+
+done_testing();
-- 
2.34.1

From df38b507278cf2f2dffb564b370b6f07c3116079 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 25 Jan 2023 10:22:41 +0100
Subject: [PATCH v10 2/4] Refactor libpq to store addrinfo in a libpq owned
 array

This refactors libpq to copy addrinfos returned by getaddrinfo to
memory owned by us. This refactoring is useful for two upcoming patches,
which need to change the addrinfo list in some way. Doing that with the
original addrinfo list is risky since we don't control how memory is
freed. Also changing the contents of a C array is quite a bit easier
than changing a linked list.

As a nice side effect of this refactor the is that mechanism for
iteration over addresses in PQconnectPoll is now identical to its
iteration over hosts.
---
 src/include/libpq/pqcomm.h        |   6 ++
 src/interfaces/libpq/fe-connect.c | 107 +++++++++++++++++++++---------
 src/interfaces/libpq/libpq-int.h  |   6 +-
 src/tools/pgindent/typedefs.list  |   1 +
 4 files changed, 87 insertions(+), 33 deletions(-)

diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index 66ba359390f..ee28e223bd7 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+} AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 97e47f05852..41deeee9a63 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -379,6 +379,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *connstr,
@@ -2077,7 +2078,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2121,11 +2122,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2272,9 +2273,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2287,6 +2288,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2327,7 +2329,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2350,8 +2352,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
 											ch->host, gai_strerror(ret));
@@ -2362,8 +2364,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
 											ch->hostaddr, gai_strerror(ret));
@@ -2372,7 +2374,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2387,8 +2389,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
 											portstr, gai_strerror(ret));
@@ -2397,8 +2399,14 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		if (!store_conn_addrinfo(conn, addrlist))
+		{
+			pg_freeaddrinfo_all(hint.ai_family, addrlist);
+			libpq_append_conn_error(conn, "out of memory");
+			goto error_return;
+		}
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2455,30 +2463,29 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2494,7 +2501,7 @@ keep_going:						/* We will come back to here until there is
 						conn->connip = strdup(host_addr);
 
 					/* Try to create the socket */
-					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
+					conn->sock = socket(addr_cur->family, SOCK_STREAM, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2505,7 +2512,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2531,7 +2538,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2558,7 +2565,7 @@ keep_going:						/* We will come back to here until there is
 					}
 #endif							/* F_SETFD */
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2650,8 +2657,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4068,6 +4075,45 @@ freePGconn(PGconn *conn)
 	free(conn);
 }
 
+/*
+ * Copies over the addrinfos from addrlist to the PGconn. The reason we do this
+ * so that we can edit the resulting list as we please, because now the memory
+ * is owned by us. Changing the original addrinfo directly is risky, since we
+ * don't control how the memory is freed and by changing it we might confuse
+ * the implementation of freeaddrinfo.
+ */
+static bool
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+		return false;
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	return true;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4075,11 +4121,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 85289980a11..4d40e8a2fbb 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -461,8 +461,10 @@ struct pg_conn
 	PGTargetServerType target_server_type;	/* desired session properties */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
+	int			naddr;			/* number of addresses returned by getaddrinfo */
+	int			whichaddr;		/* the address currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	int			addrlist_family;	/* needed to know how to free addrlist */
 	bool		send_appname;	/* okay to send application_name? */
 
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 86a9303bf56..fa8881c9d93 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -26,6 +26,7 @@ AcquireSampleRowsFunc
 ActionList
 ActiveSnapshotElt
 AddForeignUpdateTargets_function
+AddrInfo
 AffixNode
 AffixNodeData
 AfterTriggerEvent
-- 
2.34.1

From 62712a80d9664ac97630eec3f30c1a3306953aa7 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Fri, 3 Mar 2023 15:27:21 +0100
Subject: [PATCH v10 4/4] Remove unnecessary check from Fisher-Yates
 implementation

Andrey Borodin pointed out that the "undefined data check" was
unnecessary for Fisher-Yates implementations when the data that was
fetched was known to be initialized. There was one such place in the
codebase, so this removes the check there.
---
 src/backend/optimizer/geqo/geqo_recombination.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/backend/optimizer/geqo/geqo_recombination.c b/src/backend/optimizer/geqo/geqo_recombination.c
index a5d3e47ad11..53bf0cc0a42 100644
--- a/src/backend/optimizer/geqo/geqo_recombination.c
+++ b/src/backend/optimizer/geqo/geqo_recombination.c
@@ -51,9 +51,7 @@ init_tour(PlannerInfo *root, Gene *tour, int num_gene)
 	for (i = 1; i < num_gene; i++)
 	{
 		j = geqo_randint(root, i, 0);
-		/* i != j check avoids fetching uninitialized array element */
-		if (i != j)
-			tour[i] = tour[j];
+		tour[i] = tour[j];
 		tour[j] = (Gene) (i + 1);
 	}
 }
-- 
2.34.1

From 38e4e78bd0e768d03f99d50605e1782b5fdafd66 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 30 Nov 2022 10:07:19 +0100
Subject: [PATCH v10 1/4] libpq: Run pgindent after a9e9a9f32b3

It seems that pgindent was not run after the error handling refactor in
commit a9e9a9f32b35edf129c88e8b929ef223f8511f59. This fixes that and
also addresses a few other things pgindent wanted to change in libpq.
---
 src/interfaces/libpq/fe-auth-scram.c     |   2 +-
 src/interfaces/libpq/fe-auth.c           |   8 +-
 src/interfaces/libpq/fe-connect.c        | 110 +++++++++++------------
 src/interfaces/libpq/fe-exec.c           |  16 ++--
 src/interfaces/libpq/fe-lobj.c           |  42 ++++-----
 src/interfaces/libpq/fe-misc.c           |  10 +--
 src/interfaces/libpq/fe-protocol3.c      |   2 +-
 src/interfaces/libpq/fe-secure-common.c  |   6 +-
 src/interfaces/libpq/fe-secure-gssapi.c  |  12 +--
 src/interfaces/libpq/fe-secure-openssl.c |  64 ++++++-------
 src/interfaces/libpq/fe-secure.c         |   8 +-
 src/interfaces/libpq/libpq-int.h         |   4 +-
 12 files changed, 142 insertions(+), 142 deletions(-)

diff --git a/src/interfaces/libpq/fe-auth-scram.c b/src/interfaces/libpq/fe-auth-scram.c
index 9c42ea4f819..12c3d0bc333 100644
--- a/src/interfaces/libpq/fe-auth-scram.c
+++ b/src/interfaces/libpq/fe-auth-scram.c
@@ -716,7 +716,7 @@ read_server_final_message(fe_scram_state *state, char *input)
 			return false;
 		}
 		libpq_append_conn_error(conn, "error received from server in SCRAM exchange: %s",
-						   errmsg);
+								errmsg);
 		return false;
 	}
 
diff --git a/src/interfaces/libpq/fe-auth.c b/src/interfaces/libpq/fe-auth.c
index 9afc6f19b9a..ab454e6cd02 100644
--- a/src/interfaces/libpq/fe-auth.c
+++ b/src/interfaces/libpq/fe-auth.c
@@ -73,7 +73,7 @@ pg_GSS_continue(PGconn *conn, int payloadlen)
 		if (!ginbuf.value)
 		{
 			libpq_append_conn_error(conn, "out of memory allocating GSSAPI buffer (%d)",
-							  payloadlen);
+									payloadlen);
 			return STATUS_ERROR;
 		}
 		if (pqGetnchar(ginbuf.value, payloadlen, conn))
@@ -223,7 +223,7 @@ pg_SSPI_continue(PGconn *conn, int payloadlen)
 		if (!inputbuf)
 		{
 			libpq_append_conn_error(conn, "out of memory allocating SSPI buffer (%d)",
-							  payloadlen);
+									payloadlen);
 			return STATUS_ERROR;
 		}
 		if (pqGetnchar(inputbuf, payloadlen, conn))
@@ -623,7 +623,7 @@ pg_SASL_continue(PGconn *conn, int payloadlen, bool final)
 	if (!challenge)
 	{
 		libpq_append_conn_error(conn, "out of memory allocating SASL buffer (%d)",
-						  payloadlen);
+								payloadlen);
 		return STATUS_ERROR;
 	}
 
@@ -1277,7 +1277,7 @@ PQencryptPasswordConn(PGconn *conn, const char *passwd, const char *user,
 	else
 	{
 		libpq_append_conn_error(conn, "unrecognized password encryption algorithm \"%s\"",
-						  algorithm);
+								algorithm);
 		return NULL;
 	}
 
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 8f80c35c894..97e47f05852 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -1079,7 +1079,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "could not match %d host names to %d hostaddr values",
-							   count_comma_separated_elems(conn->pghost), conn->nconnhost);
+									count_comma_separated_elems(conn->pghost), conn->nconnhost);
 			return false;
 		}
 	}
@@ -1159,7 +1159,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "could not match %d port numbers to %d hosts",
-							   count_comma_separated_elems(conn->pgport), conn->nconnhost);
+									count_comma_separated_elems(conn->pgport), conn->nconnhost);
 			return false;
 		}
 	}
@@ -1248,7 +1248,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "channel_binding", conn->channel_binding);
+									"channel_binding", conn->channel_binding);
 			return false;
 		}
 	}
@@ -1273,7 +1273,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "sslmode", conn->sslmode);
+									"sslmode", conn->sslmode);
 			return false;
 		}
 
@@ -1293,7 +1293,7 @@ connectOptions2(PGconn *conn)
 			case 'v':			/* "verify-ca" or "verify-full" */
 				conn->status = CONNECTION_BAD;
 				libpq_append_conn_error(conn, "sslmode value \"%s\" invalid when SSL support is not compiled in",
-								   conn->sslmode);
+										conn->sslmode);
 				return false;
 		}
 #endif
@@ -1313,16 +1313,16 @@ connectOptions2(PGconn *conn)
 	{
 		conn->status = CONNECTION_BAD;
 		libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-						   "ssl_min_protocol_version",
-						   conn->ssl_min_protocol_version);
+								"ssl_min_protocol_version",
+								conn->ssl_min_protocol_version);
 		return false;
 	}
 	if (!sslVerifyProtocolVersion(conn->ssl_max_protocol_version))
 	{
 		conn->status = CONNECTION_BAD;
 		libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-						   "ssl_max_protocol_version",
-						   conn->ssl_max_protocol_version);
+								"ssl_max_protocol_version",
+								conn->ssl_max_protocol_version);
 		return false;
 	}
 
@@ -1359,7 +1359,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "gssencmode value \"%s\" invalid when GSSAPI support is not compiled in",
-							   conn->gssencmode);
+									conn->gssencmode);
 			return false;
 		}
 #endif
@@ -1392,8 +1392,8 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "target_session_attrs",
-							   conn->target_session_attrs);
+									"target_session_attrs",
+									conn->target_session_attrs);
 			return false;
 		}
 	}
@@ -1609,7 +1609,7 @@ connectNoDelay(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "could not set socket to TCP no delay mode: %s",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1787,7 +1787,7 @@ parse_int_param(const char *value, int *result, PGconn *conn,
 
 error:
 	libpq_append_conn_error(conn, "invalid integer value \"%s\" for connection option \"%s\"",
-					   value, context);
+							value, context);
 	return false;
 }
 
@@ -1816,9 +1816,9 @@ setKeepalivesIdle(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   PG_TCP_KEEPALIVE_IDLE_STR,
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								PG_TCP_KEEPALIVE_IDLE_STR,
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1850,9 +1850,9 @@ setKeepalivesInterval(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_KEEPINTVL",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_KEEPINTVL",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1885,9 +1885,9 @@ setKeepalivesCount(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_KEEPCNT",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_KEEPCNT",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1949,8 +1949,8 @@ prepKeepalivesWin32(PGconn *conn)
 	if (!setKeepalivesWin32(conn->sock, idle, interval))
 	{
 		libpq_append_conn_error(conn, "%s(%s) failed: error code %d",
-						  "WSAIoctl", "SIO_KEEPALIVE_VALS",
-						  WSAGetLastError());
+								"WSAIoctl", "SIO_KEEPALIVE_VALS",
+								WSAGetLastError());
 		return 0;
 	}
 	return 1;
@@ -1983,9 +1983,9 @@ setTCPUserTimeout(PGconn *conn)
 		char		sebuf[256];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_USER_TIMEOUT",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_USER_TIMEOUT",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -2354,7 +2354,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
-									   ch->host, gai_strerror(ret));
+											ch->host, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2366,7 +2366,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
-									   ch->hostaddr, gai_strerror(ret));
+											ch->hostaddr, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2377,8 +2377,8 @@ keep_going:						/* We will come back to here until there is
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
 					libpq_append_conn_error(conn, "Unix-domain socket path \"%s\" is too long (maximum %d bytes)",
-									   portstr,
-									   (int) (UNIXSOCK_PATH_BUFLEN - 1));
+											portstr,
+											(int) (UNIXSOCK_PATH_BUFLEN - 1));
 					goto keep_going;
 				}
 
@@ -2391,7 +2391,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
-									   portstr, gai_strerror(ret));
+											portstr, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2513,7 +2513,7 @@ keep_going:						/* We will come back to here until there is
 						}
 						emitHostIdentityInfo(conn, host_addr);
 						libpq_append_conn_error(conn, "could not create socket: %s",
-										   SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2543,7 +2543,7 @@ keep_going:						/* We will come back to here until there is
 					if (!pg_set_noblock(conn->sock))
 					{
 						libpq_append_conn_error(conn, "could not set socket to nonblocking mode: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						conn->try_next_addr = true;
 						goto keep_going;
 					}
@@ -2552,7 +2552,7 @@ keep_going:						/* We will come back to here until there is
 					if (fcntl(conn->sock, F_SETFD, FD_CLOEXEC) == -1)
 					{
 						libpq_append_conn_error(conn, "could not set socket to close-on-exec mode: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						conn->try_next_addr = true;
 						goto keep_going;
 					}
@@ -2581,9 +2581,9 @@ keep_going:						/* We will come back to here until there is
 											(char *) &on, sizeof(on)) < 0)
 						{
 							libpq_append_conn_error(conn, "%s(%s) failed: %s",
-											   "setsockopt",
-											   "SO_KEEPALIVE",
-											   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+													"setsockopt",
+													"SO_KEEPALIVE",
+													SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 							err = 1;
 						}
 						else if (!setKeepalivesIdle(conn)
@@ -2708,7 +2708,7 @@ keep_going:						/* We will come back to here until there is
 							   (char *) &optval, &optlen) == -1)
 				{
 					libpq_append_conn_error(conn, "could not get socket error status: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					goto error_return;
 				}
 				else if (optval != 0)
@@ -2735,7 +2735,7 @@ keep_going:						/* We will come back to here until there is
 								&conn->laddr.salen) < 0)
 				{
 					libpq_append_conn_error(conn, "could not get client address from socket: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					goto error_return;
 				}
 
@@ -2775,7 +2775,7 @@ keep_going:						/* We will come back to here until there is
 							libpq_append_conn_error(conn, "requirepeer parameter is not supported on this platform");
 						else
 							libpq_append_conn_error(conn, "could not get peer credentials: %s",
-											   strerror_r(errno, sebuf, sizeof(sebuf)));
+													strerror_r(errno, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2788,7 +2788,7 @@ keep_going:						/* We will come back to here until there is
 					if (strcmp(remote_username, conn->requirepeer) != 0)
 					{
 						libpq_append_conn_error(conn, "requirepeer specifies \"%s\", but actual peer user name is \"%s\"",
-										   conn->requirepeer, remote_username);
+												conn->requirepeer, remote_username);
 						free(remote_username);
 						goto error_return;
 					}
@@ -2829,7 +2829,7 @@ keep_going:						/* We will come back to here until there is
 					if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
 					{
 						libpq_append_conn_error(conn, "could not send GSSAPI negotiation packet: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2840,7 +2840,7 @@ keep_going:						/* We will come back to here until there is
 				else if (!conn->gctx && conn->gssencmode[0] == 'r')
 				{
 					libpq_append_conn_error(conn,
-									   "GSSAPI encryption required but was impossible (possibly no credential cache, no server support, or using a local socket)");
+											"GSSAPI encryption required but was impossible (possibly no credential cache, no server support, or using a local socket)");
 					goto error_return;
 				}
 #endif
@@ -2882,7 +2882,7 @@ keep_going:						/* We will come back to here until there is
 					if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
 					{
 						libpq_append_conn_error(conn, "could not send SSL negotiation packet: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 					/* Ok, wait for response */
@@ -2911,7 +2911,7 @@ keep_going:						/* We will come back to here until there is
 				if (pqPacketSend(conn, 0, startpacket, packetlen) != STATUS_OK)
 				{
 					libpq_append_conn_error(conn, "could not send startup packet: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					free(startpacket);
 					goto error_return;
 				}
@@ -3012,7 +3012,7 @@ keep_going:						/* We will come back to here until there is
 					else
 					{
 						libpq_append_conn_error(conn, "received invalid response to SSL negotiation: %c",
-										   SSLok);
+												SSLok);
 						goto error_return;
 					}
 				}
@@ -3123,7 +3123,7 @@ keep_going:						/* We will come back to here until there is
 					else if (gss_ok != 'G')
 					{
 						libpq_append_conn_error(conn, "received invalid response to GSSAPI negotiation: %c",
-										   gss_ok);
+												gss_ok);
 						goto error_return;
 					}
 				}
@@ -3201,7 +3201,7 @@ keep_going:						/* We will come back to here until there is
 				if (!(beresp == 'R' || beresp == 'v' || beresp == 'E'))
 				{
 					libpq_append_conn_error(conn, "expected authentication request from server, but received %c",
-									   beresp);
+											beresp);
 					goto error_return;
 				}
 
@@ -3732,7 +3732,7 @@ keep_going:						/* We will come back to here until there is
 
 				/* Append error report to conn->errorMessage. */
 				libpq_append_conn_error(conn, "\"%s\" failed",
-								  "SHOW transaction_read_only");
+										"SHOW transaction_read_only");
 
 				/* Close connection politely. */
 				conn->status = CONNECTION_OK;
@@ -3782,7 +3782,7 @@ keep_going:						/* We will come back to here until there is
 
 				/* Append error report to conn->errorMessage. */
 				libpq_append_conn_error(conn, "\"%s\" failed",
-								  "SELECT pg_is_in_recovery()");
+										"SELECT pg_is_in_recovery()");
 
 				/* Close connection politely. */
 				conn->status = CONNECTION_OK;
@@ -3795,8 +3795,8 @@ keep_going:						/* We will come back to here until there is
 
 		default:
 			libpq_append_conn_error(conn,
-							   "invalid connection state %d, probably indicative of memory corruption",
-							  conn->status);
+									"invalid connection state %d, probably indicative of memory corruption",
+									conn->status);
 			goto error_return;
 	}
 
@@ -7175,7 +7175,7 @@ pgpassfileWarning(PGconn *conn)
 
 		if (sqlstate && strcmp(sqlstate, ERRCODE_INVALID_PASSWORD) == 0)
 			libpq_append_conn_error(conn, "password retrieved from file \"%s\"",
-							  conn->pgpassfile);
+									conn->pgpassfile);
 	}
 }
 
diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index ec62550e385..0c2dae6ed9e 100644
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -1444,7 +1444,7 @@ PQsendQueryInternal(PGconn *conn, const char *query, bool newQuery)
 	if (conn->pipelineStatus != PQ_PIPELINE_OFF)
 	{
 		libpq_append_conn_error(conn, "%s not allowed in pipeline mode",
-						  "PQsendQuery");
+								"PQsendQuery");
 		return 0;
 	}
 
@@ -1512,7 +1512,7 @@ PQsendQueryParams(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1558,7 +1558,7 @@ PQsendPrepare(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1652,7 +1652,7 @@ PQsendQueryPrepared(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -2099,10 +2099,9 @@ PQgetResult(PGconn *conn)
 
 			/*
 			 * We're about to return the NULL that terminates the round of
-			 * results from the current query; prepare to send the results
-			 * of the next query, if any, when we're called next.  If there's
-			 * no next element in the command queue, this gets us in IDLE
-			 * state.
+			 * results from the current query; prepare to send the results of
+			 * the next query, if any, when we're called next.  If there's no
+			 * next element in the command queue, this gets us in IDLE state.
 			 */
 			pqPipelineProcessQueue(conn);
 			res = NULL;			/* query is complete */
@@ -3047,6 +3046,7 @@ pqPipelineProcessQueue(PGconn *conn)
 			return;
 
 		case PGASYNC_IDLE:
+
 			/*
 			 * If we're in IDLE mode and there's some command in the queue,
 			 * get us into PIPELINE_IDLE mode and process normally.  Otherwise
diff --git a/src/interfaces/libpq/fe-lobj.c b/src/interfaces/libpq/fe-lobj.c
index 4cb6a468597..206266fd043 100644
--- a/src/interfaces/libpq/fe-lobj.c
+++ b/src/interfaces/libpq/fe-lobj.c
@@ -142,7 +142,7 @@ lo_truncate(PGconn *conn, int fd, size_t len)
 	if (conn->lobjfuncs->fn_lo_truncate == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate");
+								"lo_truncate");
 		return -1;
 	}
 
@@ -205,7 +205,7 @@ lo_truncate64(PGconn *conn, int fd, pg_int64 len)
 	if (conn->lobjfuncs->fn_lo_truncate64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate64");
+								"lo_truncate64");
 		return -1;
 	}
 
@@ -395,7 +395,7 @@ lo_lseek64(PGconn *conn, int fd, pg_int64 offset, int whence)
 	if (conn->lobjfuncs->fn_lo_lseek64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek64");
+								"lo_lseek64");
 		return -1;
 	}
 
@@ -485,7 +485,7 @@ lo_create(PGconn *conn, Oid lobjId)
 	if (conn->lobjfuncs->fn_lo_create == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_create");
+								"lo_create");
 		return InvalidOid;
 	}
 
@@ -558,7 +558,7 @@ lo_tell64(PGconn *conn, int fd)
 	if (conn->lobjfuncs->fn_lo_tell64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell64");
+								"lo_tell64");
 		return -1;
 	}
 
@@ -667,7 +667,7 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 	if (fd < 0)
 	{							/* error */
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -723,8 +723,8 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not read from file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -778,8 +778,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -799,8 +799,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 			/* deliberately overwrite any error from lo_close */
 			pqClearConnErrorState(conn);
 			libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-							  filename,
-							  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+									filename,
+									strerror_r(save_errno, sebuf, sizeof(sebuf)));
 			return -1;
 		}
 	}
@@ -822,7 +822,7 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 	if (close(fd) != 0 && result >= 0)
 	{
 		libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		result = -1;
 	}
 
@@ -954,56 +954,56 @@ lo_initialize(PGconn *conn)
 	if (lobjfuncs->fn_lo_open == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_open");
+								"lo_open");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_close == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_close");
+								"lo_close");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_creat == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_creat");
+								"lo_creat");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_unlink == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_unlink");
+								"lo_unlink");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_lseek == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek");
+								"lo_lseek");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_tell == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell");
+								"lo_tell");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_read == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "loread");
+								"loread");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_write == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lowrite");
+								"lowrite");
 		free(lobjfuncs);
 		return -1;
 	}
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 3653a1a8a62..660cdec93c9 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -749,8 +749,8 @@ retry4:
 	 */
 definitelyEOF:
 	libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-					   "\tThis probably means the server terminated abnormally\n"
-					   "\tbefore or while processing the request.");
+							"\tThis probably means the server terminated abnormally\n"
+							"\tbefore or while processing the request.");
 
 	/* Come here if lower-level code already set a suitable errorMessage */
 definitelyFailed:
@@ -1067,7 +1067,7 @@ pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s() failed: %s", "select",
-						  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 	}
 
 	return result;
@@ -1280,7 +1280,7 @@ libpq_ngettext(const char *msgid, const char *msgid_plural, unsigned long n)
  * newline.
  */
 void
-libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
+libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
@@ -1309,7 +1309,7 @@ libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
  * format should not end with a newline.
  */
 void
-libpq_append_conn_error(PGconn *conn, const char *fmt, ...)
+libpq_append_conn_error(PGconn *conn, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index 8ab6a884165..b79d74f7489 100644
--- a/src/interfaces/libpq/fe-protocol3.c
+++ b/src/interfaces/libpq/fe-protocol3.c
@@ -466,7 +466,7 @@ static void
 handleSyncLoss(PGconn *conn, char id, int msgLength)
 {
 	libpq_append_conn_error(conn, "lost synchronization with server: got message type \"%c\", length %d",
-					  id, msgLength);
+							id, msgLength);
 	/* build an error result holding the error message */
 	pqSaveErrorResult(conn);
 	conn->asyncStatus = PGASYNC_READY;	/* drop out of PQgetResult wait loop */
diff --git a/src/interfaces/libpq/fe-secure-common.c b/src/interfaces/libpq/fe-secure-common.c
index de115b37649..3ecc7bf6159 100644
--- a/src/interfaces/libpq/fe-secure-common.c
+++ b/src/interfaces/libpq/fe-secure-common.c
@@ -226,7 +226,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 		 * wrong given the subject matter.
 		 */
 		libpq_append_conn_error(conn, "certificate contains IP address with invalid length %zu",
-						  iplen);
+								iplen);
 		return -1;
 	}
 
@@ -235,7 +235,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 	if (!addrstr)
 	{
 		libpq_append_conn_error(conn, "could not convert certificate's IP address to string: %s",
-						  strerror_r(errno, sebuf, sizeof(sebuf)));
+								strerror_r(errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -292,7 +292,7 @@ pq_verify_peer_name_matches_certificate(PGconn *conn)
 		else if (names_examined == 1)
 		{
 			libpq_append_conn_error(conn, "server certificate for \"%s\" does not match host name \"%s\"",
-							  first_name, host);
+									first_name, host);
 		}
 		else
 		{
diff --git a/src/interfaces/libpq/fe-secure-gssapi.c b/src/interfaces/libpq/fe-secure-gssapi.c
index 038e847b7e9..0af4de941af 100644
--- a/src/interfaces/libpq/fe-secure-gssapi.c
+++ b/src/interfaces/libpq/fe-secure-gssapi.c
@@ -213,8 +213,8 @@ pg_GSS_write(PGconn *conn, const void *ptr, size_t len)
 		if (output.length > PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "client tried to send oversize GSSAPI packet (%zu > %zu)",
-							  (size_t) output.length,
-							  PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
+									(size_t) output.length,
+									PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			goto cleanup;
 		}
@@ -349,8 +349,8 @@ pg_GSS_read(PGconn *conn, void *ptr, size_t len)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			return -1;
 		}
@@ -590,8 +590,8 @@ pqsecure_open_gss(PGconn *conn)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			return PGRES_POLLING_FAILED;
 		}
 
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index 6a4431ddfe9..e6da377fb9d 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -213,12 +213,12 @@ rloop:
 				if (result_errno == EPIPE ||
 					result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -313,12 +313,12 @@ pgtls_write(PGconn *conn, const void *ptr, size_t len)
 				result_errno = SOCK_ERRNO;
 				if (result_errno == EPIPE || result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -415,7 +415,7 @@ pgtls_get_peer_certificate_hash(PGconn *conn, size_t *len)
 			if (algo_type == NULL)
 			{
 				libpq_append_conn_error(conn, "could not find digest for NID %s",
-								  OBJ_nid2sn(algo_nid));
+										OBJ_nid2sn(algo_nid));
 				return NULL;
 			}
 			break;
@@ -967,7 +967,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_min_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for minimum SSL protocol version",
-							  conn->ssl_min_protocol_version);
+									conn->ssl_min_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -993,7 +993,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_max_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for maximum SSL protocol version",
-							  conn->ssl_max_protocol_version);
+									conn->ssl_max_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1037,7 +1037,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read root certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1089,10 +1089,10 @@ initialize_SSL(PGconn *conn)
 			 */
 			if (fnbuf[0] == '\0')
 				libpq_append_conn_error(conn, "could not get home directory to locate root certificate file\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.");
+										"Either provide the file or change sslmode to disable server certificate verification.");
 			else
 				libpq_append_conn_error(conn, "root certificate file \"%s\" does not exist\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
+										"Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1122,7 +1122,7 @@ initialize_SSL(PGconn *conn)
 		if (errno != ENOENT && errno != ENOTDIR)
 		{
 			libpq_append_conn_error(conn, "could not open certificate file \"%s\": %s",
-							  fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
+									fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1140,7 +1140,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1239,7 +1239,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				free(engine_str);
 				return -1;
@@ -1250,7 +1250,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not initialize SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				ENGINE_free(conn->engine);
 				conn->engine = NULL;
@@ -1265,7 +1265,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not read private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1278,7 +1278,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1315,10 +1315,10 @@ initialize_SSL(PGconn *conn)
 		{
 			if (errno == ENOENT)
 				libpq_append_conn_error(conn, "certificate present, but not private key file \"%s\"",
-								  fnbuf);
+										fnbuf);
 			else
 				libpq_append_conn_error(conn, "could not stat private key file \"%s\": %m",
-								  fnbuf);
+										fnbuf);
 			return -1;
 		}
 
@@ -1326,7 +1326,7 @@ initialize_SSL(PGconn *conn)
 		if (!S_ISREG(buf.st_mode))
 		{
 			libpq_append_conn_error(conn, "private key file \"%s\" is not a regular file",
-							  fnbuf);
+									fnbuf);
 			return -1;
 		}
 
@@ -1383,7 +1383,7 @@ initialize_SSL(PGconn *conn)
 			if (SSL_use_PrivateKey_file(conn->ssl, fnbuf, SSL_FILETYPE_ASN1) != 1)
 			{
 				libpq_append_conn_error(conn, "could not load private key file \"%s\": %s",
-								  fnbuf, err);
+										fnbuf, err);
 				SSLerrfree(err);
 				return -1;
 			}
@@ -1399,7 +1399,7 @@ initialize_SSL(PGconn *conn)
 		char	   *err = SSLerrmessage(ERR_get_error());
 
 		libpq_append_conn_error(conn, "certificate does not match private key file \"%s\": %s",
-						  fnbuf, err);
+								fnbuf, err);
 		SSLerrfree(err);
 		return -1;
 	}
@@ -1452,7 +1452,7 @@ open_client_SSL(PGconn *conn)
 
 					if (r == -1)
 						libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-										  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					else
 						libpq_append_conn_error(conn, "SSL SYSCALL error: EOF detected");
 					pgtls_close(conn);
@@ -1494,12 +1494,12 @@ open_client_SSL(PGconn *conn)
 						case SSL_R_VERSION_TOO_LOW:
 #endif
 							libpq_append_conn_error(conn, "This may indicate that the server does not support any SSL protocol version between %s and %s.",
-											  conn->ssl_min_protocol_version ?
-											  conn->ssl_min_protocol_version :
-											  MIN_OPENSSL_TLS_VERSION,
-											  conn->ssl_max_protocol_version ?
-											  conn->ssl_max_protocol_version :
-											  MAX_OPENSSL_TLS_VERSION);
+													conn->ssl_min_protocol_version ?
+													conn->ssl_min_protocol_version :
+													MIN_OPENSSL_TLS_VERSION,
+													conn->ssl_max_protocol_version ?
+													conn->ssl_max_protocol_version :
+													MAX_OPENSSL_TLS_VERSION);
 							break;
 						default:
 							break;
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index 66e401bf3d9..8069e381424 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -255,14 +255,14 @@ pqsecure_raw_read(PGconn *conn, void *ptr, size_t len)
 			case EPIPE:
 			case ECONNRESET:
 				libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-								   "\tThis probably means the server terminated abnormally\n"
-								   "\tbefore or while processing the request.");
+										"\tThis probably means the server terminated abnormally\n"
+										"\tbefore or while processing the request.");
 				break;
 
 			default:
 				libpq_append_conn_error(conn, "could not receive data from server: %s",
-								  SOCK_STRERROR(result_errno,
-												sebuf, sizeof(sebuf)));
+										SOCK_STRERROR(result_errno,
+													  sebuf, sizeof(sebuf)));
 				break;
 		}
 	}
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index d7ec5ed4293..85289980a11 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -888,8 +888,8 @@ extern char *libpq_ngettext(const char *msgid, const char *msgid_plural, unsigne
  */
 #undef _
 
-extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...) pg_attribute_printf(2, 3);
-extern void libpq_append_conn_error(PGconn *conn, const char *fmt, ...) pg_attribute_printf(2, 3);
+extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...) pg_attribute_printf(2, 3);
+extern void libpq_append_conn_error(PGconn *conn, const char *fmt,...) pg_attribute_printf(2, 3);
 
 /*
  * These macros are needed to let error-handling code be portable between
-- 
2.34.1

From 60fd7b0e90e2b1a7ef087b093bd3f0d486763cb2 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Fri, 3 Mar 2023 15:27:21 +0100
Subject: [PATCH v11 4/4] Remove unnecessary check from Fisher-Yates
 implementation

Andrey Borodin pointed out that the "undefined data check" was
unnecessary for Fisher-Yates implementations when the data that was
fetched was known to be initialized. There was one such place in the
codebase, so this removes the check there.
---
 src/backend/optimizer/geqo/geqo_recombination.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/backend/optimizer/geqo/geqo_recombination.c b/src/backend/optimizer/geqo/geqo_recombination.c
index a5d3e47ad11..53bf0cc0a42 100644
--- a/src/backend/optimizer/geqo/geqo_recombination.c
+++ b/src/backend/optimizer/geqo/geqo_recombination.c
@@ -51,9 +51,7 @@ init_tour(PlannerInfo *root, Gene *tour, int num_gene)
 	for (i = 1; i < num_gene; i++)
 	{
 		j = geqo_randint(root, i, 0);
-		/* i != j check avoids fetching uninitialized array element */
-		if (i != j)
-			tour[i] = tour[j];
+		tour[i] = tour[j];
 		tour[j] = (Gene) (i + 1);
 	}
 }
-- 
2.34.1

From 8e9e76292daae4f19cc7a629e0c41df2eba9590a Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 25 Jan 2023 10:22:41 +0100
Subject: [PATCH v11 2/4] Refactor libpq to store addrinfo in a libpq owned
 array

This refactors libpq to copy addrinfos returned by getaddrinfo to
memory owned by us. This refactoring is useful for two upcoming patches,
which need to change the addrinfo list in some way. Doing that with the
original addrinfo list is risky since we don't control how memory is
freed. Also changing the contents of a C array is quite a bit easier
than changing a linked list.

As a nice side effect of this refactor the is that mechanism for
iteration over addresses in PQconnectPoll is now identical to its
iteration over hosts.
---
 src/include/libpq/pqcomm.h        |   6 ++
 src/interfaces/libpq/fe-connect.c | 107 +++++++++++++++++++++---------
 src/interfaces/libpq/libpq-int.h  |   6 +-
 src/tools/pgindent/typedefs.list  |   1 +
 4 files changed, 87 insertions(+), 33 deletions(-)

diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index 66ba359390f..ee28e223bd7 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+} AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 97e47f05852..41deeee9a63 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -379,6 +379,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *connstr,
@@ -2077,7 +2078,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2121,11 +2122,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2272,9 +2273,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2287,6 +2288,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2327,7 +2329,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2350,8 +2352,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
 											ch->host, gai_strerror(ret));
@@ -2362,8 +2364,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
 											ch->hostaddr, gai_strerror(ret));
@@ -2372,7 +2374,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2387,8 +2389,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
 											portstr, gai_strerror(ret));
@@ -2397,8 +2399,14 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		if (!store_conn_addrinfo(conn, addrlist))
+		{
+			pg_freeaddrinfo_all(hint.ai_family, addrlist);
+			libpq_append_conn_error(conn, "out of memory");
+			goto error_return;
+		}
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2455,30 +2463,29 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2494,7 +2501,7 @@ keep_going:						/* We will come back to here until there is
 						conn->connip = strdup(host_addr);
 
 					/* Try to create the socket */
-					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
+					conn->sock = socket(addr_cur->family, SOCK_STREAM, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2505,7 +2512,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2531,7 +2538,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2558,7 +2565,7 @@ keep_going:						/* We will come back to here until there is
 					}
 #endif							/* F_SETFD */
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2650,8 +2657,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4068,6 +4075,45 @@ freePGconn(PGconn *conn)
 	free(conn);
 }
 
+/*
+ * Copies over the addrinfos from addrlist to the PGconn. The reason we do this
+ * so that we can edit the resulting list as we please, because now the memory
+ * is owned by us. Changing the original addrinfo directly is risky, since we
+ * don't control how the memory is freed and by changing it we might confuse
+ * the implementation of freeaddrinfo.
+ */
+static bool
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+		return false;
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	return true;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4075,11 +4121,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 85289980a11..4d40e8a2fbb 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -461,8 +461,10 @@ struct pg_conn
 	PGTargetServerType target_server_type;	/* desired session properties */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
+	int			naddr;			/* number of addresses returned by getaddrinfo */
+	int			whichaddr;		/* the address currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	int			addrlist_family;	/* needed to know how to free addrlist */
 	bool		send_appname;	/* okay to send application_name? */
 
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 86a9303bf56..fa8881c9d93 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -26,6 +26,7 @@ AcquireSampleRowsFunc
 ActionList
 ActiveSnapshotElt
 AddForeignUpdateTargets_function
+AddrInfo
 AffixNode
 AffixNodeData
 AfterTriggerEvent
-- 
2.34.1

From 151a6d02c843e629189a86b56ded2f7707e69886 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <github-tech@jeltef.nl>
Date: Mon, 12 Sep 2022 09:44:06 +0200
Subject: [PATCH v11 3/4] Support load balancing in libpq

This adds support for load balancing to libpq using the newly added
load_balance_hosts parameter. When setting the load_balance_hosts
parameter to random, hosts and addresses will be connected to in a
random order. This then results in load balancing across these
hosts/addresses if multiple clients do this at the same time.

This patch implements two levels of random load balancing:
1. The given hosts are randomly shuffled, before resolving them
    one-by-one.
2. Once a host its addresses get resolved, those addresses are shuffled,
    before trying to connect to them one-by-one.
---
 .cirrus.yml                                   |  16 ++-
 doc/src/sgml/libpq.sgml                       |  69 ++++++++++
 doc/src/sgml/regress.sgml                     |  11 +-
 src/interfaces/libpq/fe-connect.c             | 118 ++++++++++++++++++
 src/interfaces/libpq/libpq-int.h              |  18 ++-
 src/interfaces/libpq/meson.build              |   2 +
 .../libpq/t/003_loadbalance_host_list.pl      |  76 +++++++++++
 src/interfaces/libpq/t/004_loadbalance_dns.pl | 103 +++++++++++++++
 8 files changed, 410 insertions(+), 3 deletions(-)
 create mode 100644 src/interfaces/libpq/t/003_loadbalance_host_list.pl
 create mode 100644 src/interfaces/libpq/t/004_loadbalance_dns.pl

diff --git a/.cirrus.yml b/.cirrus.yml
index f2129787529..51f810a4031 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -25,7 +25,7 @@ env:
   MTEST_ARGS: --print-errorlogs --no-rebuild -C build
   PGCTLTIMEOUT: 120 # avoids spurious failures during parallel tests
   TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
-  PG_TEST_EXTRA: kerberos ldap ssl
+  PG_TEST_EXTRA: kerberos ldap ssl loadbalance
 
 
 # What files to preserve in case tests fail
@@ -314,6 +314,14 @@ task:
     mkdir -m 770 /tmp/cores
     chown root:postgres /tmp/cores
     sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core'
+
+  setup_hosts_file_script: |
+    cat >> /etc/hosts <<-EOF
+      127.0.0.1 pg-loadbalancetest
+      127.0.0.2 pg-loadbalancetest
+      127.0.0.3 pg-loadbalancetest
+    EOF
+
   setup_additional_packages_script: |
     #apt-get update
     #DEBIAN_FRONTEND=noninteractive apt-get -y install ...
@@ -565,6 +573,12 @@ task:
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
+  setup_hosts_file_script: |
+    echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    type c:\Windows\System32\Drivers\etc\hosts
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 3ccd8ff9421..004749487d5 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1964,6 +1964,75 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="libpq-connect-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls the order in which the client tries to connect to the available
+        hosts and addresses. It's typically used in combination with multiple
+        host names or a DNS record that returns multiple IPs. This parameter can
+        be used in combination with <xref linkend="libpq-connect-target-session-attrs"/>
+        to, for example, load balance over stanby servers only. Once successfully
+        connected, subsequent queries on the returned connection will all be
+        sent to the same server. There are currently two modes:
+        <variablelist>
+         <varlistentry>
+          <term><literal>disable</literal> (default)</term>
+          <listitem>
+           <para>
+            Hosts are tried in the order in which they are provided and
+            addresses are tried in the order they are received from DNS or a
+            hosts file.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>random</literal></term>
+          <listitem>
+           <para>
+            The provided hosts and the addresses that they resolve to are
+            tried in random order. This value is mostly useful when opening
+            multiple connections at the same time, possibly from different
+            machines. This way connections can be load balanced across multiple
+            Postgres servers.
+           </para>
+           <para>
+            This algorithm uses two levels of random choices: First the hosts
+            will be resolved in random order. Then before resolving the next
+            host, all resolved addresses for the current host will be tried in
+            random order. This behaviour can lead to non-uniform address
+            selection in certain cases, for instance when some hosts resolve to
+            more addresses than others. So if you want uniform load balancing,
+            this is something to keep in mind. However, non-uniform load
+            balancing can also be used to your advantage, e.g. by providing the
+            hostname of a larger server multiple times in the host string so it
+            gets more connections.
+           </para>
+           <para>
+            When using this value it's recommended to also configure a reasonable
+            value for <xref linkend="libpq-connect-connect-timeout"/>. Because then,
+            if one of the nodes that are used for load balancing is not responding,
+            a new node will be tried.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-random-seed" xreflabel="random_seed">
+      <term><literal>random_seed</literal></term>
+      <listitem>
+       <para>
+        Sets the random seed that is used by <xref linkend="libpq-connect-load-balance-hosts"/>
+        to randomize the host order. This option is mostly useful when running
+        tests that require a stable random order.
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
    </para>
   </sect2>
diff --git a/doc/src/sgml/regress.sgml b/doc/src/sgml/regress.sgml
index a08c7a78af8..026ac05c755 100644
--- a/doc/src/sgml/regress.sgml
+++ b/doc/src/sgml/regress.sgml
@@ -256,7 +256,7 @@ make check-world -j8 >/dev/null
    <varname>PG_TEST_EXTRA</varname> to a whitespace-separated list, for
    example:
 <programlisting>
-make check-world PG_TEST_EXTRA='kerberos ldap ssl'
+make check-world PG_TEST_EXTRA='kerberos ldap ssl loadbalance'
 </programlisting>
    The following values are currently supported:
    <variablelist>
@@ -290,6 +290,15 @@ make check-world PG_TEST_EXTRA='kerberos ldap ssl'
      </listitem>
     </varlistentry>
 
+    <varlistentry>
+     <term><literal>loadbalance</literal></term>
+     <listitem>
+      <para>
+       Runs the test <filename>src/interfaces/libpq/t/004_loadbalance_dns.pl</filename>.  This opens TCP/IP listen sockets.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry>
      <term><literal>wal_consistency_checking</literal></term>
      <listitem>
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 41deeee9a63..b2fb47272a3 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -123,6 +123,7 @@ static int	ldapServiceLookup(const char *purl, PQconninfoOption *options,
 #define DefaultChannelBinding	"disable"
 #endif
 #define DefaultTargetSessionAttrs	"any"
+#define DefaultLoadBalanceHosts	"disable"
 #ifdef USE_SSL
 #define DefaultSSLMode "prefer"
 #else
@@ -341,6 +342,15 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Target-Session-Attrs", "", 15, /* sizeof("prefer-standby") = 15 */
 	offsetof(struct pg_conn, target_session_attrs)},
 
+	{"load_balance_hosts", "PGLOADBALANCEHOSTS",
+		DefaultLoadBalanceHosts, NULL,
+		"Load-Balance-Hosts", "", 8,	/* sizeof("disable") = 8 */
+	offsetof(struct pg_conn, load_balance_hosts)},
+
+	{"random_seed", NULL, NULL, NULL,
+		"Random-Seed", "", 10,	/* strlen(INT32_MAX) == 10 */
+	offsetof(struct pg_conn, randomseed)},
+
 	/* Terminating entry --- MUST BE LAST */
 	{NULL, NULL, NULL, NULL,
 	NULL, NULL, 0}
@@ -425,6 +435,8 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static bool parse_int_param(const char *value, int *result, PGconn *conn,
+							const char *context);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1008,6 +1020,40 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on timestamp and PID.
+ */
+static bool
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(conn->randomseed))
+	{
+		int			rseed;
+
+		if (!parse_int_param(conn->randomseed, &rseed, conn, "random_seed"))
+			return false;
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	else if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		struct timeval tval = {0};
+
+		gettimeofday(&tval, NULL);
+
+		rseed = ((uint64) conn) ^
+			((uint64) getpid()) ^
+			((uint64) tval.tv_usec) ^
+			((uint64) tval.tv_sec);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	return true;
+}
+
 /*
  *		connectOptions2
  *
@@ -1401,6 +1447,50 @@ connectOptions2(PGconn *conn)
 	else
 		conn->target_server_type = SERVER_TYPE_ANY;
 
+	/*
+	 * validate load_balance_hosts option, and set load_balance_type
+	 */
+	if (conn->load_balance_hosts)
+	{
+		if (strcmp(conn->load_balance_hosts, "disable") == 0)
+			conn->load_balance_type = LOAD_BALANCE_DISABLE;
+		else if (strcmp(conn->load_balance_hosts, "random") == 0)
+			conn->load_balance_type = LOAD_BALANCE_RANDOM;
+		else
+		{
+			conn->status = CONNECTION_BAD;
+			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
+									"load_balance_hosts",
+									conn->load_balance_hosts);
+			return false;
+		}
+	}
+	else
+		conn->load_balance_type = LOAD_BALANCE_DISABLE;
+
+	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+	{
+		if (!libpq_prng_init(conn))
+			return false;
+
+		/*
+		 * This is the "inside-out" variant of the Fisher-Yates shuffle
+		 * algorithm. Notionally, we append each new value to the array and
+		 * then swap it with a randomly-chosen array element (possibly
+		 * including itself, else we fail to generate permutations with the
+		 * last integer last).  The swap step can be optimized by combining it
+		 * with the insertion.
+		 */
+		for (i = 1; i < conn->nconnhost; i++)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
 	/*
 	 * Resolve special "auto" client_encoding from the locale
 	 */
@@ -2407,6 +2497,32 @@ keep_going:						/* We will come back to here until there is
 		}
 		pg_freeaddrinfo_all(hint.ai_family, addrlist);
 
+		/*
+		 * If random load balancing is enabled we shuffle the addresses.
+		 */
+		if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+		{
+			/*
+			 * This is the "inside-out" variant of the Fisher-Yates shuffle
+			 * algorithm. Notionally, we append each new value to the array
+			 * and then swap it with a randomly-chosen array element (possibly
+			 * including itself, else we fail to generate permutations with
+			 * the last integer last).  The swap step can be optimized by
+			 * combining it with the insertion.
+			 *
+			 * We don't need to initialize conn->prng_state here, because that
+			 * already happened in connectOptions2.
+			 */
+			for (int i = 1; i < conn->naddr; i++)
+			{
+				int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+				AddrInfo	temp = conn->addr[j];
+
+				conn->addr[j] = conn->addr[i];
+				conn->addr[i] = temp;
+			}
+		}
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -4069,6 +4185,8 @@ freePGconn(PGconn *conn)
 	free(conn->outBuffer);
 	free(conn->rowBuf);
 	free(conn->target_session_attrs);
+	free(conn->load_balance_hosts);
+	free(conn->randomseed);
 	termPQExpBuffer(&conn->errorMessage);
 	termPQExpBuffer(&conn->workBuffer);
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 4d40e8a2fbb..0fabe969c70 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -26,7 +26,8 @@
 #include <netdb.h>
 #include <sys/socket.h>
 #include <time.h>
-#ifndef WIN32
+/* MinGW has sys/time.h, but MSVC doesn't */
+#ifndef _MSC_VER
 #include <sys/time.h>
 #endif
 
@@ -82,6 +83,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -242,6 +245,13 @@ typedef enum
 	SERVER_TYPE_PREFER_STANDBY_PASS2	/* second pass - behaves same as ANY */
 } PGTargetServerType;
 
+/* Target server type (decoded value of load_balance_hosts) */
+typedef enum
+{
+	LOAD_BALANCE_DISABLE = 0,	/* Use the existing host order (default) */
+	LOAD_BALANCE_RANDOM,		/* Read-write server */
+}			PGLoadBalanceType;
+
 /* Boolean value plus a not-known state, for GUCs we might have to fetch */
 typedef enum
 {
@@ -396,6 +406,8 @@ struct pg_conn
 	char	   *ssl_min_protocol_version;	/* minimum TLS protocol version */
 	char	   *ssl_max_protocol_version;	/* maximum TLS protocol version */
 	char	   *target_session_attrs;	/* desired session properties */
+	char	   *load_balance_hosts; /* load balance over hosts */
+	char	   *randomseed;		/* seed for randomization of load balancing */
 
 	/* Optional file to write trace info to */
 	FILE	   *Pfdebug;
@@ -459,6 +471,8 @@ struct pg_conn
 
 	/* Transient state needed while establishing connection */
 	PGTargetServerType target_server_type;	/* desired session properties */
+	PGLoadBalanceType load_balance_type;	/* desired load balancing
+											 * algorithm */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
 	int			naddr;			/* number of addresses returned by getaddrinfo */
@@ -479,6 +493,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index 573fd9b6ea4..edebb014362 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -116,6 +116,8 @@ tests += {
     'tests': [
       't/001_uri.pl',
       't/002_api.pl',
+      't/003_loadbalance_host_list.pl',
+      't/004_loadbalance_dns.pl',
     ],
     'env': {'with_ssl': get_option('ssl')},
   },
diff --git a/src/interfaces/libpq/t/003_loadbalance_host_list.pl b/src/interfaces/libpq/t/003_loadbalance_host_list.pl
new file mode 100644
index 00000000000..547b7d34fa4
--- /dev/null
+++ b/src/interfaces/libpq/t/003_loadbalance_host_list.pl
@@ -0,0 +1,76 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests load balancing across the list of different hosts in the host
+# parameter of the connection string.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $node1 = PostgreSQL::Test::Cluster->new('node1');
+my $node2 = PostgreSQL::Test::Cluster->new('node2', own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# Start the tests for load balancing method 1
+my $hostlist = $node1->host . ',' . $node2->host . ',' . $node3->host;
+my $portlist = $node1->port . ',' . $node2->port . ',' . $node3->port;
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 selects node 1 first",
+	sql => "SELECT 'connect1'",
+	log_like => [qr/statement: SELECT 'connect1'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 does not select node 2 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 does not select node 3 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 selects node 3 first",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 1 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node3->stop();
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does select node 1 second",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 second",
+	sql => "SELECT 'connect3'",
+	log_unlike => [qr/statement: SELECT 'connect3'/]);
+
+$node3->start();
+
+done_testing();
+
diff --git a/src/interfaces/libpq/t/004_loadbalance_dns.pl b/src/interfaces/libpq/t/004_loadbalance_dns.pl
new file mode 100644
index 00000000000..2512c41c466
--- /dev/null
+++ b/src/interfaces/libpq/t/004_loadbalance_dns.pl
@@ -0,0 +1,103 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests loadbalancing based on a DNS entry that contains multiple records
+# for different IPs. Since setting up a DNS server is more effort than we
+# consider reasonable to run this test, this situation is instead immitated by
+# using a hosts file where a single hostname maps to multiple different IP
+# addresses. This test requires the adminstrator to add the following lines to
+# the hosts file (if we detect that this hasn't happend we skip the test):
+#
+# 127.0.0.1 pg-loadbalancetest
+# 127.0.0.2 pg-loadbalancetest
+# 127.0.0.3 pg-loadbalancetest
+#
+# Windows or Linux are required to run this test because these OSes allow
+# binding to 127.0.0.2 and 127.0.0.3 addresess by default, but other OSes
+# don't. We need to bind to different IP addresses, so that we can use these
+# different IP addresses in the hosts file.
+#
+# The hosts file needs to be prepared before running this test. We don't do it
+# on the fly, because it requires root permissions to change the hosts file. In
+# CI we set up the previously mentioned rules in the hosts file, so that this
+# load balancing method is tested.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os;
+
+# Checks for the requirements for testing load balancing method 2
+if (!$can_bind_to_127_0_0_2) {
+	plan skip_all => "OS could not bind to 127.0.0.2"
+}
+
+my $hosts_path;
+if ($windows_os) {
+	$hosts_path = 'c:\Windows\System32\Drivers\etc\hosts';
+}
+else
+{
+	$hosts_path = '/etc/hosts';
+}
+
+my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path);
+
+if ($hosts_content !~ m/pg-loadbalancetest/) {
+	# Host file is not prepared for this test
+	plan skip_all => "hosts file was not prepared for DNS load balance test"
+}
+
+if ($ENV{PG_TEST_EXTRA} !~ /\bloadbalance\b/)
+{
+	plan skip_all => 'Potentially unsafe test loadbalance not enabled in PG_TEST_EXTRA';
+}
+
+$PostgreSQL::Test::Cluster::use_tcp = 1;
+$PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1';
+my $port = PostgreSQL::Test::Cluster::get_free_port();
+my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port);
+my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+$node2->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 selects node 2 first",
+	sql => "SELECT 'connect4'",
+	log_like => [qr/statement: SELECT 'connect4'/]);
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 1 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 3 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node2->stop();
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does select node 1 second",
+	sql => "SELECT 'connect5'",
+	log_like => [qr/statement: SELECT 'connect5'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 3 second",
+	sql => "SELECT 'connect5'",
+	log_unlike => [qr/statement: SELECT 'connect5'/]);
+
+done_testing();
-- 
2.34.1

From 5862544275aad236395d5fae4f12b2c0771a0a78 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 30 Nov 2022 10:07:19 +0100
Subject: [PATCH v11 1/4] libpq: Run pgindent after a9e9a9f32b3

It seems that pgindent was not run after the error handling refactor in
commit a9e9a9f32b35edf129c88e8b929ef223f8511f59. This fixes that and
also addresses a few other things pgindent wanted to change in libpq.
---
 src/interfaces/libpq/fe-auth-scram.c     |   2 +-
 src/interfaces/libpq/fe-auth.c           |   8 +-
 src/interfaces/libpq/fe-connect.c        | 110 +++++++++++------------
 src/interfaces/libpq/fe-exec.c           |  16 ++--
 src/interfaces/libpq/fe-lobj.c           |  42 ++++-----
 src/interfaces/libpq/fe-misc.c           |  10 +--
 src/interfaces/libpq/fe-protocol3.c      |   2 +-
 src/interfaces/libpq/fe-secure-common.c  |   6 +-
 src/interfaces/libpq/fe-secure-gssapi.c  |  12 +--
 src/interfaces/libpq/fe-secure-openssl.c |  64 ++++++-------
 src/interfaces/libpq/fe-secure.c         |   8 +-
 src/interfaces/libpq/libpq-int.h         |   4 +-
 12 files changed, 142 insertions(+), 142 deletions(-)

diff --git a/src/interfaces/libpq/fe-auth-scram.c b/src/interfaces/libpq/fe-auth-scram.c
index 9c42ea4f819..12c3d0bc333 100644
--- a/src/interfaces/libpq/fe-auth-scram.c
+++ b/src/interfaces/libpq/fe-auth-scram.c
@@ -716,7 +716,7 @@ read_server_final_message(fe_scram_state *state, char *input)
 			return false;
 		}
 		libpq_append_conn_error(conn, "error received from server in SCRAM exchange: %s",
-						   errmsg);
+								errmsg);
 		return false;
 	}
 
diff --git a/src/interfaces/libpq/fe-auth.c b/src/interfaces/libpq/fe-auth.c
index 9afc6f19b9a..ab454e6cd02 100644
--- a/src/interfaces/libpq/fe-auth.c
+++ b/src/interfaces/libpq/fe-auth.c
@@ -73,7 +73,7 @@ pg_GSS_continue(PGconn *conn, int payloadlen)
 		if (!ginbuf.value)
 		{
 			libpq_append_conn_error(conn, "out of memory allocating GSSAPI buffer (%d)",
-							  payloadlen);
+									payloadlen);
 			return STATUS_ERROR;
 		}
 		if (pqGetnchar(ginbuf.value, payloadlen, conn))
@@ -223,7 +223,7 @@ pg_SSPI_continue(PGconn *conn, int payloadlen)
 		if (!inputbuf)
 		{
 			libpq_append_conn_error(conn, "out of memory allocating SSPI buffer (%d)",
-							  payloadlen);
+									payloadlen);
 			return STATUS_ERROR;
 		}
 		if (pqGetnchar(inputbuf, payloadlen, conn))
@@ -623,7 +623,7 @@ pg_SASL_continue(PGconn *conn, int payloadlen, bool final)
 	if (!challenge)
 	{
 		libpq_append_conn_error(conn, "out of memory allocating SASL buffer (%d)",
-						  payloadlen);
+								payloadlen);
 		return STATUS_ERROR;
 	}
 
@@ -1277,7 +1277,7 @@ PQencryptPasswordConn(PGconn *conn, const char *passwd, const char *user,
 	else
 	{
 		libpq_append_conn_error(conn, "unrecognized password encryption algorithm \"%s\"",
-						  algorithm);
+								algorithm);
 		return NULL;
 	}
 
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 8f80c35c894..97e47f05852 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -1079,7 +1079,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "could not match %d host names to %d hostaddr values",
-							   count_comma_separated_elems(conn->pghost), conn->nconnhost);
+									count_comma_separated_elems(conn->pghost), conn->nconnhost);
 			return false;
 		}
 	}
@@ -1159,7 +1159,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "could not match %d port numbers to %d hosts",
-							   count_comma_separated_elems(conn->pgport), conn->nconnhost);
+									count_comma_separated_elems(conn->pgport), conn->nconnhost);
 			return false;
 		}
 	}
@@ -1248,7 +1248,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "channel_binding", conn->channel_binding);
+									"channel_binding", conn->channel_binding);
 			return false;
 		}
 	}
@@ -1273,7 +1273,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "sslmode", conn->sslmode);
+									"sslmode", conn->sslmode);
 			return false;
 		}
 
@@ -1293,7 +1293,7 @@ connectOptions2(PGconn *conn)
 			case 'v':			/* "verify-ca" or "verify-full" */
 				conn->status = CONNECTION_BAD;
 				libpq_append_conn_error(conn, "sslmode value \"%s\" invalid when SSL support is not compiled in",
-								   conn->sslmode);
+										conn->sslmode);
 				return false;
 		}
 #endif
@@ -1313,16 +1313,16 @@ connectOptions2(PGconn *conn)
 	{
 		conn->status = CONNECTION_BAD;
 		libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-						   "ssl_min_protocol_version",
-						   conn->ssl_min_protocol_version);
+								"ssl_min_protocol_version",
+								conn->ssl_min_protocol_version);
 		return false;
 	}
 	if (!sslVerifyProtocolVersion(conn->ssl_max_protocol_version))
 	{
 		conn->status = CONNECTION_BAD;
 		libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-						   "ssl_max_protocol_version",
-						   conn->ssl_max_protocol_version);
+								"ssl_max_protocol_version",
+								conn->ssl_max_protocol_version);
 		return false;
 	}
 
@@ -1359,7 +1359,7 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "gssencmode value \"%s\" invalid when GSSAPI support is not compiled in",
-							   conn->gssencmode);
+									conn->gssencmode);
 			return false;
 		}
 #endif
@@ -1392,8 +1392,8 @@ connectOptions2(PGconn *conn)
 		{
 			conn->status = CONNECTION_BAD;
 			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
-							   "target_session_attrs",
-							   conn->target_session_attrs);
+									"target_session_attrs",
+									conn->target_session_attrs);
 			return false;
 		}
 	}
@@ -1609,7 +1609,7 @@ connectNoDelay(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "could not set socket to TCP no delay mode: %s",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1787,7 +1787,7 @@ parse_int_param(const char *value, int *result, PGconn *conn,
 
 error:
 	libpq_append_conn_error(conn, "invalid integer value \"%s\" for connection option \"%s\"",
-					   value, context);
+							value, context);
 	return false;
 }
 
@@ -1816,9 +1816,9 @@ setKeepalivesIdle(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   PG_TCP_KEEPALIVE_IDLE_STR,
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								PG_TCP_KEEPALIVE_IDLE_STR,
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1850,9 +1850,9 @@ setKeepalivesInterval(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_KEEPINTVL",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_KEEPINTVL",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1885,9 +1885,9 @@ setKeepalivesCount(PGconn *conn)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_KEEPCNT",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_KEEPCNT",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -1949,8 +1949,8 @@ prepKeepalivesWin32(PGconn *conn)
 	if (!setKeepalivesWin32(conn->sock, idle, interval))
 	{
 		libpq_append_conn_error(conn, "%s(%s) failed: error code %d",
-						  "WSAIoctl", "SIO_KEEPALIVE_VALS",
-						  WSAGetLastError());
+								"WSAIoctl", "SIO_KEEPALIVE_VALS",
+								WSAGetLastError());
 		return 0;
 	}
 	return 1;
@@ -1983,9 +1983,9 @@ setTCPUserTimeout(PGconn *conn)
 		char		sebuf[256];
 
 		libpq_append_conn_error(conn, "%s(%s) failed: %s",
-						   "setsockopt",
-						   "TCP_USER_TIMEOUT",
-						   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								"setsockopt",
+								"TCP_USER_TIMEOUT",
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 		return 0;
 	}
 #endif
@@ -2354,7 +2354,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
-									   ch->host, gai_strerror(ret));
+											ch->host, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2366,7 +2366,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
-									   ch->hostaddr, gai_strerror(ret));
+											ch->hostaddr, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2377,8 +2377,8 @@ keep_going:						/* We will come back to here until there is
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
 					libpq_append_conn_error(conn, "Unix-domain socket path \"%s\" is too long (maximum %d bytes)",
-									   portstr,
-									   (int) (UNIXSOCK_PATH_BUFLEN - 1));
+											portstr,
+											(int) (UNIXSOCK_PATH_BUFLEN - 1));
 					goto keep_going;
 				}
 
@@ -2391,7 +2391,7 @@ keep_going:						/* We will come back to here until there is
 				if (ret || !conn->addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
-									   portstr, gai_strerror(ret));
+											portstr, gai_strerror(ret));
 					goto keep_going;
 				}
 				break;
@@ -2513,7 +2513,7 @@ keep_going:						/* We will come back to here until there is
 						}
 						emitHostIdentityInfo(conn, host_addr);
 						libpq_append_conn_error(conn, "could not create socket: %s",
-										   SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(errorno, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2543,7 +2543,7 @@ keep_going:						/* We will come back to here until there is
 					if (!pg_set_noblock(conn->sock))
 					{
 						libpq_append_conn_error(conn, "could not set socket to nonblocking mode: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						conn->try_next_addr = true;
 						goto keep_going;
 					}
@@ -2552,7 +2552,7 @@ keep_going:						/* We will come back to here until there is
 					if (fcntl(conn->sock, F_SETFD, FD_CLOEXEC) == -1)
 					{
 						libpq_append_conn_error(conn, "could not set socket to close-on-exec mode: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						conn->try_next_addr = true;
 						goto keep_going;
 					}
@@ -2581,9 +2581,9 @@ keep_going:						/* We will come back to here until there is
 											(char *) &on, sizeof(on)) < 0)
 						{
 							libpq_append_conn_error(conn, "%s(%s) failed: %s",
-											   "setsockopt",
-											   "SO_KEEPALIVE",
-											   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+													"setsockopt",
+													"SO_KEEPALIVE",
+													SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 							err = 1;
 						}
 						else if (!setKeepalivesIdle(conn)
@@ -2708,7 +2708,7 @@ keep_going:						/* We will come back to here until there is
 							   (char *) &optval, &optlen) == -1)
 				{
 					libpq_append_conn_error(conn, "could not get socket error status: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					goto error_return;
 				}
 				else if (optval != 0)
@@ -2735,7 +2735,7 @@ keep_going:						/* We will come back to here until there is
 								&conn->laddr.salen) < 0)
 				{
 					libpq_append_conn_error(conn, "could not get client address from socket: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					goto error_return;
 				}
 
@@ -2775,7 +2775,7 @@ keep_going:						/* We will come back to here until there is
 							libpq_append_conn_error(conn, "requirepeer parameter is not supported on this platform");
 						else
 							libpq_append_conn_error(conn, "could not get peer credentials: %s",
-											   strerror_r(errno, sebuf, sizeof(sebuf)));
+													strerror_r(errno, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2788,7 +2788,7 @@ keep_going:						/* We will come back to here until there is
 					if (strcmp(remote_username, conn->requirepeer) != 0)
 					{
 						libpq_append_conn_error(conn, "requirepeer specifies \"%s\", but actual peer user name is \"%s\"",
-										   conn->requirepeer, remote_username);
+												conn->requirepeer, remote_username);
 						free(remote_username);
 						goto error_return;
 					}
@@ -2829,7 +2829,7 @@ keep_going:						/* We will come back to here until there is
 					if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
 					{
 						libpq_append_conn_error(conn, "could not send GSSAPI negotiation packet: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 
@@ -2840,7 +2840,7 @@ keep_going:						/* We will come back to here until there is
 				else if (!conn->gctx && conn->gssencmode[0] == 'r')
 				{
 					libpq_append_conn_error(conn,
-									   "GSSAPI encryption required but was impossible (possibly no credential cache, no server support, or using a local socket)");
+											"GSSAPI encryption required but was impossible (possibly no credential cache, no server support, or using a local socket)");
 					goto error_return;
 				}
 #endif
@@ -2882,7 +2882,7 @@ keep_going:						/* We will come back to here until there is
 					if (pqPacketSend(conn, 0, &pv, sizeof(pv)) != STATUS_OK)
 					{
 						libpq_append_conn_error(conn, "could not send SSL negotiation packet: %s",
-										   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 						goto error_return;
 					}
 					/* Ok, wait for response */
@@ -2911,7 +2911,7 @@ keep_going:						/* We will come back to here until there is
 				if (pqPacketSend(conn, 0, startpacket, packetlen) != STATUS_OK)
 				{
 					libpq_append_conn_error(conn, "could not send startup packet: %s",
-									   SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					free(startpacket);
 					goto error_return;
 				}
@@ -3012,7 +3012,7 @@ keep_going:						/* We will come back to here until there is
 					else
 					{
 						libpq_append_conn_error(conn, "received invalid response to SSL negotiation: %c",
-										   SSLok);
+												SSLok);
 						goto error_return;
 					}
 				}
@@ -3123,7 +3123,7 @@ keep_going:						/* We will come back to here until there is
 					else if (gss_ok != 'G')
 					{
 						libpq_append_conn_error(conn, "received invalid response to GSSAPI negotiation: %c",
-										   gss_ok);
+												gss_ok);
 						goto error_return;
 					}
 				}
@@ -3201,7 +3201,7 @@ keep_going:						/* We will come back to here until there is
 				if (!(beresp == 'R' || beresp == 'v' || beresp == 'E'))
 				{
 					libpq_append_conn_error(conn, "expected authentication request from server, but received %c",
-									   beresp);
+											beresp);
 					goto error_return;
 				}
 
@@ -3732,7 +3732,7 @@ keep_going:						/* We will come back to here until there is
 
 				/* Append error report to conn->errorMessage. */
 				libpq_append_conn_error(conn, "\"%s\" failed",
-								  "SHOW transaction_read_only");
+										"SHOW transaction_read_only");
 
 				/* Close connection politely. */
 				conn->status = CONNECTION_OK;
@@ -3782,7 +3782,7 @@ keep_going:						/* We will come back to here until there is
 
 				/* Append error report to conn->errorMessage. */
 				libpq_append_conn_error(conn, "\"%s\" failed",
-								  "SELECT pg_is_in_recovery()");
+										"SELECT pg_is_in_recovery()");
 
 				/* Close connection politely. */
 				conn->status = CONNECTION_OK;
@@ -3795,8 +3795,8 @@ keep_going:						/* We will come back to here until there is
 
 		default:
 			libpq_append_conn_error(conn,
-							   "invalid connection state %d, probably indicative of memory corruption",
-							  conn->status);
+									"invalid connection state %d, probably indicative of memory corruption",
+									conn->status);
 			goto error_return;
 	}
 
@@ -7175,7 +7175,7 @@ pgpassfileWarning(PGconn *conn)
 
 		if (sqlstate && strcmp(sqlstate, ERRCODE_INVALID_PASSWORD) == 0)
 			libpq_append_conn_error(conn, "password retrieved from file \"%s\"",
-							  conn->pgpassfile);
+									conn->pgpassfile);
 	}
 }
 
diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index ec62550e385..0c2dae6ed9e 100644
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -1444,7 +1444,7 @@ PQsendQueryInternal(PGconn *conn, const char *query, bool newQuery)
 	if (conn->pipelineStatus != PQ_PIPELINE_OFF)
 	{
 		libpq_append_conn_error(conn, "%s not allowed in pipeline mode",
-						  "PQsendQuery");
+								"PQsendQuery");
 		return 0;
 	}
 
@@ -1512,7 +1512,7 @@ PQsendQueryParams(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1558,7 +1558,7 @@ PQsendPrepare(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1652,7 +1652,7 @@ PQsendQueryPrepared(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -2099,10 +2099,9 @@ PQgetResult(PGconn *conn)
 
 			/*
 			 * We're about to return the NULL that terminates the round of
-			 * results from the current query; prepare to send the results
-			 * of the next query, if any, when we're called next.  If there's
-			 * no next element in the command queue, this gets us in IDLE
-			 * state.
+			 * results from the current query; prepare to send the results of
+			 * the next query, if any, when we're called next.  If there's no
+			 * next element in the command queue, this gets us in IDLE state.
 			 */
 			pqPipelineProcessQueue(conn);
 			res = NULL;			/* query is complete */
@@ -3047,6 +3046,7 @@ pqPipelineProcessQueue(PGconn *conn)
 			return;
 
 		case PGASYNC_IDLE:
+
 			/*
 			 * If we're in IDLE mode and there's some command in the queue,
 			 * get us into PIPELINE_IDLE mode and process normally.  Otherwise
diff --git a/src/interfaces/libpq/fe-lobj.c b/src/interfaces/libpq/fe-lobj.c
index 4cb6a468597..206266fd043 100644
--- a/src/interfaces/libpq/fe-lobj.c
+++ b/src/interfaces/libpq/fe-lobj.c
@@ -142,7 +142,7 @@ lo_truncate(PGconn *conn, int fd, size_t len)
 	if (conn->lobjfuncs->fn_lo_truncate == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate");
+								"lo_truncate");
 		return -1;
 	}
 
@@ -205,7 +205,7 @@ lo_truncate64(PGconn *conn, int fd, pg_int64 len)
 	if (conn->lobjfuncs->fn_lo_truncate64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate64");
+								"lo_truncate64");
 		return -1;
 	}
 
@@ -395,7 +395,7 @@ lo_lseek64(PGconn *conn, int fd, pg_int64 offset, int whence)
 	if (conn->lobjfuncs->fn_lo_lseek64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek64");
+								"lo_lseek64");
 		return -1;
 	}
 
@@ -485,7 +485,7 @@ lo_create(PGconn *conn, Oid lobjId)
 	if (conn->lobjfuncs->fn_lo_create == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_create");
+								"lo_create");
 		return InvalidOid;
 	}
 
@@ -558,7 +558,7 @@ lo_tell64(PGconn *conn, int fd)
 	if (conn->lobjfuncs->fn_lo_tell64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell64");
+								"lo_tell64");
 		return -1;
 	}
 
@@ -667,7 +667,7 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 	if (fd < 0)
 	{							/* error */
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -723,8 +723,8 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not read from file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -778,8 +778,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -799,8 +799,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 			/* deliberately overwrite any error from lo_close */
 			pqClearConnErrorState(conn);
 			libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-							  filename,
-							  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+									filename,
+									strerror_r(save_errno, sebuf, sizeof(sebuf)));
 			return -1;
 		}
 	}
@@ -822,7 +822,7 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 	if (close(fd) != 0 && result >= 0)
 	{
 		libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		result = -1;
 	}
 
@@ -954,56 +954,56 @@ lo_initialize(PGconn *conn)
 	if (lobjfuncs->fn_lo_open == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_open");
+								"lo_open");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_close == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_close");
+								"lo_close");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_creat == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_creat");
+								"lo_creat");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_unlink == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_unlink");
+								"lo_unlink");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_lseek == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek");
+								"lo_lseek");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_tell == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell");
+								"lo_tell");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_read == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "loread");
+								"loread");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_write == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lowrite");
+								"lowrite");
 		free(lobjfuncs);
 		return -1;
 	}
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 3653a1a8a62..660cdec93c9 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -749,8 +749,8 @@ retry4:
 	 */
 definitelyEOF:
 	libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-					   "\tThis probably means the server terminated abnormally\n"
-					   "\tbefore or while processing the request.");
+							"\tThis probably means the server terminated abnormally\n"
+							"\tbefore or while processing the request.");
 
 	/* Come here if lower-level code already set a suitable errorMessage */
 definitelyFailed:
@@ -1067,7 +1067,7 @@ pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s() failed: %s", "select",
-						  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 	}
 
 	return result;
@@ -1280,7 +1280,7 @@ libpq_ngettext(const char *msgid, const char *msgid_plural, unsigned long n)
  * newline.
  */
 void
-libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
+libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
@@ -1309,7 +1309,7 @@ libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
  * format should not end with a newline.
  */
 void
-libpq_append_conn_error(PGconn *conn, const char *fmt, ...)
+libpq_append_conn_error(PGconn *conn, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index 8ab6a884165..b79d74f7489 100644
--- a/src/interfaces/libpq/fe-protocol3.c
+++ b/src/interfaces/libpq/fe-protocol3.c
@@ -466,7 +466,7 @@ static void
 handleSyncLoss(PGconn *conn, char id, int msgLength)
 {
 	libpq_append_conn_error(conn, "lost synchronization with server: got message type \"%c\", length %d",
-					  id, msgLength);
+							id, msgLength);
 	/* build an error result holding the error message */
 	pqSaveErrorResult(conn);
 	conn->asyncStatus = PGASYNC_READY;	/* drop out of PQgetResult wait loop */
diff --git a/src/interfaces/libpq/fe-secure-common.c b/src/interfaces/libpq/fe-secure-common.c
index de115b37649..3ecc7bf6159 100644
--- a/src/interfaces/libpq/fe-secure-common.c
+++ b/src/interfaces/libpq/fe-secure-common.c
@@ -226,7 +226,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 		 * wrong given the subject matter.
 		 */
 		libpq_append_conn_error(conn, "certificate contains IP address with invalid length %zu",
-						  iplen);
+								iplen);
 		return -1;
 	}
 
@@ -235,7 +235,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 	if (!addrstr)
 	{
 		libpq_append_conn_error(conn, "could not convert certificate's IP address to string: %s",
-						  strerror_r(errno, sebuf, sizeof(sebuf)));
+								strerror_r(errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -292,7 +292,7 @@ pq_verify_peer_name_matches_certificate(PGconn *conn)
 		else if (names_examined == 1)
 		{
 			libpq_append_conn_error(conn, "server certificate for \"%s\" does not match host name \"%s\"",
-							  first_name, host);
+									first_name, host);
 		}
 		else
 		{
diff --git a/src/interfaces/libpq/fe-secure-gssapi.c b/src/interfaces/libpq/fe-secure-gssapi.c
index 038e847b7e9..0af4de941af 100644
--- a/src/interfaces/libpq/fe-secure-gssapi.c
+++ b/src/interfaces/libpq/fe-secure-gssapi.c
@@ -213,8 +213,8 @@ pg_GSS_write(PGconn *conn, const void *ptr, size_t len)
 		if (output.length > PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "client tried to send oversize GSSAPI packet (%zu > %zu)",
-							  (size_t) output.length,
-							  PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
+									(size_t) output.length,
+									PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			goto cleanup;
 		}
@@ -349,8 +349,8 @@ pg_GSS_read(PGconn *conn, void *ptr, size_t len)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			return -1;
 		}
@@ -590,8 +590,8 @@ pqsecure_open_gss(PGconn *conn)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			return PGRES_POLLING_FAILED;
 		}
 
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index 6a4431ddfe9..e6da377fb9d 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -213,12 +213,12 @@ rloop:
 				if (result_errno == EPIPE ||
 					result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -313,12 +313,12 @@ pgtls_write(PGconn *conn, const void *ptr, size_t len)
 				result_errno = SOCK_ERRNO;
 				if (result_errno == EPIPE || result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -415,7 +415,7 @@ pgtls_get_peer_certificate_hash(PGconn *conn, size_t *len)
 			if (algo_type == NULL)
 			{
 				libpq_append_conn_error(conn, "could not find digest for NID %s",
-								  OBJ_nid2sn(algo_nid));
+										OBJ_nid2sn(algo_nid));
 				return NULL;
 			}
 			break;
@@ -967,7 +967,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_min_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for minimum SSL protocol version",
-							  conn->ssl_min_protocol_version);
+									conn->ssl_min_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -993,7 +993,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_max_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for maximum SSL protocol version",
-							  conn->ssl_max_protocol_version);
+									conn->ssl_max_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1037,7 +1037,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read root certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1089,10 +1089,10 @@ initialize_SSL(PGconn *conn)
 			 */
 			if (fnbuf[0] == '\0')
 				libpq_append_conn_error(conn, "could not get home directory to locate root certificate file\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.");
+										"Either provide the file or change sslmode to disable server certificate verification.");
 			else
 				libpq_append_conn_error(conn, "root certificate file \"%s\" does not exist\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
+										"Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1122,7 +1122,7 @@ initialize_SSL(PGconn *conn)
 		if (errno != ENOENT && errno != ENOTDIR)
 		{
 			libpq_append_conn_error(conn, "could not open certificate file \"%s\": %s",
-							  fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
+									fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1140,7 +1140,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1239,7 +1239,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				free(engine_str);
 				return -1;
@@ -1250,7 +1250,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not initialize SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				ENGINE_free(conn->engine);
 				conn->engine = NULL;
@@ -1265,7 +1265,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not read private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1278,7 +1278,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1315,10 +1315,10 @@ initialize_SSL(PGconn *conn)
 		{
 			if (errno == ENOENT)
 				libpq_append_conn_error(conn, "certificate present, but not private key file \"%s\"",
-								  fnbuf);
+										fnbuf);
 			else
 				libpq_append_conn_error(conn, "could not stat private key file \"%s\": %m",
-								  fnbuf);
+										fnbuf);
 			return -1;
 		}
 
@@ -1326,7 +1326,7 @@ initialize_SSL(PGconn *conn)
 		if (!S_ISREG(buf.st_mode))
 		{
 			libpq_append_conn_error(conn, "private key file \"%s\" is not a regular file",
-							  fnbuf);
+									fnbuf);
 			return -1;
 		}
 
@@ -1383,7 +1383,7 @@ initialize_SSL(PGconn *conn)
 			if (SSL_use_PrivateKey_file(conn->ssl, fnbuf, SSL_FILETYPE_ASN1) != 1)
 			{
 				libpq_append_conn_error(conn, "could not load private key file \"%s\": %s",
-								  fnbuf, err);
+										fnbuf, err);
 				SSLerrfree(err);
 				return -1;
 			}
@@ -1399,7 +1399,7 @@ initialize_SSL(PGconn *conn)
 		char	   *err = SSLerrmessage(ERR_get_error());
 
 		libpq_append_conn_error(conn, "certificate does not match private key file \"%s\": %s",
-						  fnbuf, err);
+								fnbuf, err);
 		SSLerrfree(err);
 		return -1;
 	}
@@ -1452,7 +1452,7 @@ open_client_SSL(PGconn *conn)
 
 					if (r == -1)
 						libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-										  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					else
 						libpq_append_conn_error(conn, "SSL SYSCALL error: EOF detected");
 					pgtls_close(conn);
@@ -1494,12 +1494,12 @@ open_client_SSL(PGconn *conn)
 						case SSL_R_VERSION_TOO_LOW:
 #endif
 							libpq_append_conn_error(conn, "This may indicate that the server does not support any SSL protocol version between %s and %s.",
-											  conn->ssl_min_protocol_version ?
-											  conn->ssl_min_protocol_version :
-											  MIN_OPENSSL_TLS_VERSION,
-											  conn->ssl_max_protocol_version ?
-											  conn->ssl_max_protocol_version :
-											  MAX_OPENSSL_TLS_VERSION);
+													conn->ssl_min_protocol_version ?
+													conn->ssl_min_protocol_version :
+													MIN_OPENSSL_TLS_VERSION,
+													conn->ssl_max_protocol_version ?
+													conn->ssl_max_protocol_version :
+													MAX_OPENSSL_TLS_VERSION);
 							break;
 						default:
 							break;
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index 66e401bf3d9..8069e381424 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -255,14 +255,14 @@ pqsecure_raw_read(PGconn *conn, void *ptr, size_t len)
 			case EPIPE:
 			case ECONNRESET:
 				libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-								   "\tThis probably means the server terminated abnormally\n"
-								   "\tbefore or while processing the request.");
+										"\tThis probably means the server terminated abnormally\n"
+										"\tbefore or while processing the request.");
 				break;
 
 			default:
 				libpq_append_conn_error(conn, "could not receive data from server: %s",
-								  SOCK_STRERROR(result_errno,
-												sebuf, sizeof(sebuf)));
+										SOCK_STRERROR(result_errno,
+													  sebuf, sizeof(sebuf)));
 				break;
 		}
 	}
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index d7ec5ed4293..85289980a11 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -888,8 +888,8 @@ extern char *libpq_ngettext(const char *msgid, const char *msgid_plural, unsigne
  */
 #undef _
 
-extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...) pg_attribute_printf(2, 3);
-extern void libpq_append_conn_error(PGconn *conn, const char *fmt, ...) pg_attribute_printf(2, 3);
+extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...) pg_attribute_printf(2, 3);
+extern void libpq_append_conn_error(PGconn *conn, const char *fmt,...) pg_attribute_printf(2, 3);
 
 /*
  * These macros are needed to let error-handling code be portable between
-- 
2.34.1

From 6007648869efe67b9cdd1dd0d5855b9c7105baa4 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 25 Jan 2023 10:22:41 +0100
Subject: [PATCH v12 2/4] Refactor libpq to store addrinfo in a libpq owned
 array

This refactors libpq to copy addrinfos returned by getaddrinfo to
memory owned by us. This refactoring is useful for two upcoming patches,
which need to change the addrinfo list in some way. Doing that with the
original addrinfo list is risky since we don't control how memory is
freed. Also changing the contents of a C array is quite a bit easier
than changing a linked list.

As a nice side effect of this refactor the is that mechanism for
iteration over addresses in PQconnectPoll is now identical to its
iteration over hosts.
---
 src/include/libpq/pqcomm.h        |   6 ++
 src/interfaces/libpq/fe-connect.c | 107 +++++++++++++++++++++---------
 src/interfaces/libpq/libpq-int.h  |   6 +-
 src/tools/pgindent/typedefs.list  |   1 +
 4 files changed, 87 insertions(+), 33 deletions(-)

diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index 5268d442abe..507ee825824 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+} AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index dd4b98e0998..b085892feac 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -383,6 +383,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *connstr,
@@ -2246,7 +2247,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2290,11 +2291,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2441,9 +2442,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2456,6 +2457,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2496,7 +2498,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2519,8 +2521,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
 											ch->host, gai_strerror(ret));
@@ -2531,8 +2533,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
 											ch->hostaddr, gai_strerror(ret));
@@ -2541,7 +2543,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2556,8 +2558,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
 											portstr, gai_strerror(ret));
@@ -2566,8 +2568,14 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		if (!store_conn_addrinfo(conn, addrlist))
+		{
+			pg_freeaddrinfo_all(hint.ai_family, addrlist);
+			libpq_append_conn_error(conn, "out of memory");
+			goto error_return;
+		}
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2624,30 +2632,29 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2663,7 +2670,7 @@ keep_going:						/* We will come back to here until there is
 						conn->connip = strdup(host_addr);
 
 					/* Try to create the socket */
-					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
+					conn->sock = socket(addr_cur->family, SOCK_STREAM, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2674,7 +2681,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2700,7 +2707,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2727,7 +2734,7 @@ keep_going:						/* We will come back to here until there is
 					}
 #endif							/* F_SETFD */
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2819,8 +2826,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4243,6 +4250,45 @@ freePGconn(PGconn *conn)
 	free(conn);
 }
 
+/*
+ * Copies over the addrinfos from addrlist to the PGconn. The reason we do this
+ * so that we can edit the resulting list as we please, because now the memory
+ * is owned by us. Changing the original addrinfo directly is risky, since we
+ * don't control how the memory is freed and by changing it we might confuse
+ * the implementation of freeaddrinfo.
+ */
+static bool
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+		return false;
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	return true;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4250,11 +4296,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 8890525cdf4..cf10ea15aa1 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -470,8 +470,10 @@ struct pg_conn
 	PGTargetServerType target_server_type;	/* desired session properties */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
+	int			naddr;			/* number of addresses returned by getaddrinfo */
+	int			whichaddr;		/* the address currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	int			addrlist_family;	/* needed to know how to free addrlist */
 	bool		send_appname;	/* okay to send application_name? */
 
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 86a9303bf56..fa8881c9d93 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -26,6 +26,7 @@ AcquireSampleRowsFunc
 ActionList
 ActiveSnapshotElt
 AddForeignUpdateTargets_function
+AddrInfo
 AffixNode
 AffixNodeData
 AfterTriggerEvent
-- 
2.34.1

From 119159103e1f7ce74afb7ccbd69355440ab76d36 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <github-tech@jeltef.nl>
Date: Mon, 12 Sep 2022 09:44:06 +0200
Subject: [PATCH v12 3/4] Support load balancing in libpq

This adds support for load balancing to libpq using the newly added
load_balance_hosts parameter. When setting the load_balance_hosts
parameter to random, hosts and addresses will be connected to in a
random order. This then results in load balancing across these
hosts/addresses if multiple clients do this at the same time.

This patch implements two levels of random load balancing:
1. The given hosts are randomly shuffled, before resolving them
    one-by-one.
2. Once a host its addresses get resolved, those addresses are shuffled,
    before trying to connect to them one-by-one.
---
 .cirrus.yml                                   |  16 ++-
 doc/src/sgml/libpq.sgml                       |  69 ++++++++++
 doc/src/sgml/regress.sgml                     |  11 +-
 src/interfaces/libpq/fe-connect.c             | 118 ++++++++++++++++++
 src/interfaces/libpq/libpq-int.h              |  18 ++-
 src/interfaces/libpq/meson.build              |   2 +
 .../libpq/t/003_loadbalance_host_list.pl      |  76 +++++++++++
 src/interfaces/libpq/t/004_loadbalance_dns.pl | 103 +++++++++++++++
 8 files changed, 410 insertions(+), 3 deletions(-)
 create mode 100644 src/interfaces/libpq/t/003_loadbalance_host_list.pl
 create mode 100644 src/interfaces/libpq/t/004_loadbalance_dns.pl

diff --git a/.cirrus.yml b/.cirrus.yml
index 505c50f3285..9f0f882c03c 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -25,7 +25,7 @@ env:
   MTEST_ARGS: --print-errorlogs --no-rebuild -C build
   PGCTLTIMEOUT: 120 # avoids spurious failures during parallel tests
   TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
-  PG_TEST_EXTRA: kerberos ldap ssl
+  PG_TEST_EXTRA: kerberos ldap ssl loadbalance
 
 
 # What files to preserve in case tests fail
@@ -313,6 +313,14 @@ task:
     mkdir -m 770 /tmp/cores
     chown root:postgres /tmp/cores
     sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core'
+
+  setup_hosts_file_script: |
+    cat >> /etc/hosts <<-EOF
+      127.0.0.1 pg-loadbalancetest
+      127.0.0.2 pg-loadbalancetest
+      127.0.0.3 pg-loadbalancetest
+    EOF
+
   setup_additional_packages_script: |
     #apt-get update
     #DEBIAN_FRONTEND=noninteractive apt-get -y install ...
@@ -564,6 +572,12 @@ task:
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
+  setup_hosts_file_script: |
+    echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    type c:\Windows\System32\Drivers\etc\hosts
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 3706d349abc..8ae168f5f7e 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -2069,6 +2069,75 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="libpq-connect-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls the order in which the client tries to connect to the available
+        hosts and addresses. It's typically used in combination with multiple
+        host names or a DNS record that returns multiple IPs. This parameter can
+        be used in combination with <xref linkend="libpq-connect-target-session-attrs"/>
+        to, for example, load balance over stanby servers only. Once successfully
+        connected, subsequent queries on the returned connection will all be
+        sent to the same server. There are currently two modes:
+        <variablelist>
+         <varlistentry>
+          <term><literal>disable</literal> (default)</term>
+          <listitem>
+           <para>
+            Hosts are tried in the order in which they are provided and
+            addresses are tried in the order they are received from DNS or a
+            hosts file.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>random</literal></term>
+          <listitem>
+           <para>
+            The provided hosts and the addresses that they resolve to are
+            tried in random order. This value is mostly useful when opening
+            multiple connections at the same time, possibly from different
+            machines. This way connections can be load balanced across multiple
+            Postgres servers.
+           </para>
+           <para>
+            This algorithm uses two levels of random choices: First the hosts
+            will be resolved in random order. Then before resolving the next
+            host, all resolved addresses for the current host will be tried in
+            random order. This behaviour can lead to non-uniform address
+            selection in certain cases, for instance when some hosts resolve to
+            more addresses than others. So if you want uniform load balancing,
+            this is something to keep in mind. However, non-uniform load
+            balancing can also be used to your advantage, e.g. by providing the
+            hostname of a larger server multiple times in the host string so it
+            gets more connections.
+           </para>
+           <para>
+            When using this value it's recommended to also configure a reasonable
+            value for <xref linkend="libpq-connect-connect-timeout"/>. Because then,
+            if one of the nodes that are used for load balancing is not responding,
+            a new node will be tried.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="libpq-random-seed" xreflabel="random_seed">
+      <term><literal>random_seed</literal></term>
+      <listitem>
+       <para>
+        Sets the random seed that is used by <xref linkend="libpq-connect-load-balance-hosts"/>
+        to randomize the host order. This option is mostly useful when running
+        tests that require a stable random order.
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
    </para>
   </sect2>
diff --git a/doc/src/sgml/regress.sgml b/doc/src/sgml/regress.sgml
index 719e0a76985..8dda17b1362 100644
--- a/doc/src/sgml/regress.sgml
+++ b/doc/src/sgml/regress.sgml
@@ -256,7 +256,7 @@ make check-world -j8 >/dev/null
    <varname>PG_TEST_EXTRA</varname> to a whitespace-separated list, for
    example:
 <programlisting>
-make check-world PG_TEST_EXTRA='kerberos ldap ssl'
+make check-world PG_TEST_EXTRA='kerberos ldap ssl loadbalance'
 </programlisting>
    The following values are currently supported:
    <variablelist>
@@ -290,6 +290,15 @@ make check-world PG_TEST_EXTRA='kerberos ldap ssl'
      </listitem>
     </varlistentry>
 
+    <varlistentry>
+     <term><literal>loadbalance</literal></term>
+     <listitem>
+      <para>
+       Runs the test <filename>src/interfaces/libpq/t/004_loadbalance_dns.pl</filename>.  This opens TCP/IP listen sockets.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry>
      <term><literal>wal_consistency_checking</literal></term>
      <listitem>
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index b085892feac..806a9d69a2d 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -123,6 +123,7 @@ static int	ldapServiceLookup(const char *purl, PQconninfoOption *options,
 #define DefaultChannelBinding	"disable"
 #endif
 #define DefaultTargetSessionAttrs	"any"
+#define DefaultLoadBalanceHosts	"disable"
 #ifdef USE_SSL
 #define DefaultSSLMode "prefer"
 #else
@@ -345,6 +346,15 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Target-Session-Attrs", "", 15, /* sizeof("prefer-standby") = 15 */
 	offsetof(struct pg_conn, target_session_attrs)},
 
+	{"load_balance_hosts", "PGLOADBALANCEHOSTS",
+		DefaultLoadBalanceHosts, NULL,
+		"Load-Balance-Hosts", "", 8,	/* sizeof("disable") = 8 */
+	offsetof(struct pg_conn, load_balance_hosts)},
+
+	{"random_seed", NULL, NULL, NULL,
+		"Random-Seed", "", 10,	/* strlen(INT32_MAX) == 10 */
+	offsetof(struct pg_conn, randomseed)},
+
 	/* Terminating entry --- MUST BE LAST */
 	{NULL, NULL, NULL, NULL,
 	NULL, NULL, 0}
@@ -429,6 +439,8 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static bool parse_int_param(const char *value, int *result, PGconn *conn,
+							const char *context);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1013,6 +1025,40 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on timestamp and PID.
+ */
+static bool
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(conn->randomseed))
+	{
+		int			rseed;
+
+		if (!parse_int_param(conn->randomseed, &rseed, conn, "random_seed"))
+			return false;
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	else if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		struct timeval tval = {0};
+
+		gettimeofday(&tval, NULL);
+
+		rseed = ((uint64) conn) ^
+			((uint64) getpid()) ^
+			((uint64) tval.tv_usec) ^
+			((uint64) tval.tv_sec);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	return true;
+}
+
 /*
  *		connectOptions2
  *
@@ -1570,6 +1616,50 @@ connectOptions2(PGconn *conn)
 	else
 		conn->target_server_type = SERVER_TYPE_ANY;
 
+	/*
+	 * validate load_balance_hosts option, and set load_balance_type
+	 */
+	if (conn->load_balance_hosts)
+	{
+		if (strcmp(conn->load_balance_hosts, "disable") == 0)
+			conn->load_balance_type = LOAD_BALANCE_DISABLE;
+		else if (strcmp(conn->load_balance_hosts, "random") == 0)
+			conn->load_balance_type = LOAD_BALANCE_RANDOM;
+		else
+		{
+			conn->status = CONNECTION_BAD;
+			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
+									"load_balance_hosts",
+									conn->load_balance_hosts);
+			return false;
+		}
+	}
+	else
+		conn->load_balance_type = LOAD_BALANCE_DISABLE;
+
+	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+	{
+		if (!libpq_prng_init(conn))
+			return false;
+
+		/*
+		 * This is the "inside-out" variant of the Fisher-Yates shuffle
+		 * algorithm. Notionally, we append each new value to the array and
+		 * then swap it with a randomly-chosen array element (possibly
+		 * including itself, else we fail to generate permutations with the
+		 * last integer last).  The swap step can be optimized by combining it
+		 * with the insertion.
+		 */
+		for (i = 1; i < conn->nconnhost; i++)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
 	/*
 	 * Resolve special "auto" client_encoding from the locale
 	 */
@@ -2576,6 +2666,32 @@ keep_going:						/* We will come back to here until there is
 		}
 		pg_freeaddrinfo_all(hint.ai_family, addrlist);
 
+		/*
+		 * If random load balancing is enabled we shuffle the addresses.
+		 */
+		if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+		{
+			/*
+			 * This is the "inside-out" variant of the Fisher-Yates shuffle
+			 * algorithm. Notionally, we append each new value to the array
+			 * and then swap it with a randomly-chosen array element (possibly
+			 * including itself, else we fail to generate permutations with
+			 * the last integer last).  The swap step can be optimized by
+			 * combining it with the insertion.
+			 *
+			 * We don't need to initialize conn->prng_state here, because that
+			 * already happened in connectOptions2.
+			 */
+			for (int i = 1; i < conn->naddr; i++)
+			{
+				int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+				AddrInfo	temp = conn->addr[j];
+
+				conn->addr[j] = conn->addr[i];
+				conn->addr[i] = temp;
+			}
+		}
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -4244,6 +4360,8 @@ freePGconn(PGconn *conn)
 	free(conn->outBuffer);
 	free(conn->rowBuf);
 	free(conn->target_session_attrs);
+	free(conn->load_balance_hosts);
+	free(conn->randomseed);
 	termPQExpBuffer(&conn->errorMessage);
 	termPQExpBuffer(&conn->workBuffer);
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index cf10ea15aa1..f8e301ae335 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -26,7 +26,8 @@
 #include <netdb.h>
 #include <sys/socket.h>
 #include <time.h>
-#ifndef WIN32
+/* MinGW has sys/time.h, but MSVC doesn't */
+#ifndef _MSC_VER
 #include <sys/time.h>
 #endif
 
@@ -82,6 +83,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -242,6 +245,13 @@ typedef enum
 	SERVER_TYPE_PREFER_STANDBY_PASS2	/* second pass - behaves same as ANY */
 } PGTargetServerType;
 
+/* Target server type (decoded value of load_balance_hosts) */
+typedef enum
+{
+	LOAD_BALANCE_DISABLE = 0,	/* Use the existing host order (default) */
+	LOAD_BALANCE_RANDOM,		/* Read-write server */
+}			PGLoadBalanceType;
+
 /* Boolean value plus a not-known state, for GUCs we might have to fetch */
 typedef enum
 {
@@ -397,6 +407,8 @@ struct pg_conn
 	char	   *ssl_max_protocol_version;	/* maximum TLS protocol version */
 	char	   *target_session_attrs;	/* desired session properties */
 	char	   *require_auth;	/* name of the expected auth method */
+	char	   *load_balance_hosts; /* load balance over hosts */
+	char	   *randomseed;		/* seed for randomization of load balancing */
 
 	/* Optional file to write trace info to */
 	FILE	   *Pfdebug;
@@ -468,6 +480,8 @@ struct pg_conn
 
 	/* Transient state needed while establishing connection */
 	PGTargetServerType target_server_type;	/* desired session properties */
+	PGLoadBalanceType load_balance_type;	/* desired load balancing
+											 * algorithm */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
 	int			naddr;			/* number of addresses returned by getaddrinfo */
@@ -488,6 +502,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index 3cd0ddb4945..1b44d49a238 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -116,6 +116,8 @@ tests += {
     'tests': [
       't/001_uri.pl',
       't/002_api.pl',
+      't/003_loadbalance_host_list.pl',
+      't/004_loadbalance_dns.pl',
     ],
     'env': {'with_ssl': ssl_library},
   },
diff --git a/src/interfaces/libpq/t/003_loadbalance_host_list.pl b/src/interfaces/libpq/t/003_loadbalance_host_list.pl
new file mode 100644
index 00000000000..547b7d34fa4
--- /dev/null
+++ b/src/interfaces/libpq/t/003_loadbalance_host_list.pl
@@ -0,0 +1,76 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests load balancing across the list of different hosts in the host
+# parameter of the connection string.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $node1 = PostgreSQL::Test::Cluster->new('node1');
+my $node2 = PostgreSQL::Test::Cluster->new('node2', own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# Start the tests for load balancing method 1
+my $hostlist = $node1->host . ',' . $node2->host . ',' . $node3->host;
+my $portlist = $node1->port . ',' . $node2->port . ',' . $node3->port;
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 selects node 1 first",
+	sql => "SELECT 'connect1'",
+	log_like => [qr/statement: SELECT 'connect1'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 does not select node 2 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=1234",
+	"seed 1234 does not select node 3 first",
+	sql => "SELECT 'connect1'",
+	log_unlike => [qr/statement: SELECT 'connect1'/]);
+
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 selects node 3 first",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 1 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 first",
+	sql => "SELECT 'connect2'",
+	log_unlike => [qr/statement: SELECT 'connect2'/]);
+
+$node3->stop();
+
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does select node 1 second",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random random_seed=42",
+	"seed 42 does not select node 2 second",
+	sql => "SELECT 'connect3'",
+	log_unlike => [qr/statement: SELECT 'connect3'/]);
+
+$node3->start();
+
+done_testing();
+
diff --git a/src/interfaces/libpq/t/004_loadbalance_dns.pl b/src/interfaces/libpq/t/004_loadbalance_dns.pl
new file mode 100644
index 00000000000..2512c41c466
--- /dev/null
+++ b/src/interfaces/libpq/t/004_loadbalance_dns.pl
@@ -0,0 +1,103 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests loadbalancing based on a DNS entry that contains multiple records
+# for different IPs. Since setting up a DNS server is more effort than we
+# consider reasonable to run this test, this situation is instead immitated by
+# using a hosts file where a single hostname maps to multiple different IP
+# addresses. This test requires the adminstrator to add the following lines to
+# the hosts file (if we detect that this hasn't happend we skip the test):
+#
+# 127.0.0.1 pg-loadbalancetest
+# 127.0.0.2 pg-loadbalancetest
+# 127.0.0.3 pg-loadbalancetest
+#
+# Windows or Linux are required to run this test because these OSes allow
+# binding to 127.0.0.2 and 127.0.0.3 addresess by default, but other OSes
+# don't. We need to bind to different IP addresses, so that we can use these
+# different IP addresses in the hosts file.
+#
+# The hosts file needs to be prepared before running this test. We don't do it
+# on the fly, because it requires root permissions to change the hosts file. In
+# CI we set up the previously mentioned rules in the hosts file, so that this
+# load balancing method is tested.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os;
+
+# Checks for the requirements for testing load balancing method 2
+if (!$can_bind_to_127_0_0_2) {
+	plan skip_all => "OS could not bind to 127.0.0.2"
+}
+
+my $hosts_path;
+if ($windows_os) {
+	$hosts_path = 'c:\Windows\System32\Drivers\etc\hosts';
+}
+else
+{
+	$hosts_path = '/etc/hosts';
+}
+
+my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path);
+
+if ($hosts_content !~ m/pg-loadbalancetest/) {
+	# Host file is not prepared for this test
+	plan skip_all => "hosts file was not prepared for DNS load balance test"
+}
+
+if ($ENV{PG_TEST_EXTRA} !~ /\bloadbalance\b/)
+{
+	plan skip_all => 'Potentially unsafe test loadbalance not enabled in PG_TEST_EXTRA';
+}
+
+$PostgreSQL::Test::Cluster::use_tcp = 1;
+$PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1';
+my $port = PostgreSQL::Test::Cluster::get_free_port();
+my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port);
+my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+$node2->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 selects node 2 first",
+	sql => "SELECT 'connect4'",
+	log_like => [qr/statement: SELECT 'connect4'/]);
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 1 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 3 first",
+	sql => "SELECT 'connect4'",
+	log_unlike => [qr/statement: SELECT 'connect4'/]);
+
+$node2->stop();
+
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does select node 1 second",
+	sql => "SELECT 'connect5'",
+	log_like => [qr/statement: SELECT 'connect5'/]);
+
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random random_seed=33",
+	"seed 33 does not select node 3 second",
+	sql => "SELECT 'connect5'",
+	log_unlike => [qr/statement: SELECT 'connect5'/]);
+
+done_testing();
-- 
2.34.1

From 58810ddb8dddab5d434619e2bd7b5daff2587a6f Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 30 Nov 2022 10:07:19 +0100
Subject: [PATCH v12 1/4] libpq: Run pgindent after a9e9a9f32b3

It seems that pgindent was not run after the error handling refactor in
commit a9e9a9f32b35edf129c88e8b929ef223f8511f59. This fixes that and
also addresses a few other things pgindent wanted to change in libpq.
---
 src/interfaces/libpq/fe-exec.c           | 16 +++---
 src/interfaces/libpq/fe-lobj.c           | 42 ++++++++--------
 src/interfaces/libpq/fe-misc.c           | 10 ++--
 src/interfaces/libpq/fe-protocol3.c      |  2 +-
 src/interfaces/libpq/fe-secure-common.c  |  6 +--
 src/interfaces/libpq/fe-secure-gssapi.c  | 12 ++---
 src/interfaces/libpq/fe-secure-openssl.c | 64 ++++++++++++------------
 src/interfaces/libpq/fe-secure.c         |  8 +--
 src/interfaces/libpq/libpq-int.h         |  4 +-
 9 files changed, 82 insertions(+), 82 deletions(-)

diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index ec62550e385..0c2dae6ed9e 100644
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -1444,7 +1444,7 @@ PQsendQueryInternal(PGconn *conn, const char *query, bool newQuery)
 	if (conn->pipelineStatus != PQ_PIPELINE_OFF)
 	{
 		libpq_append_conn_error(conn, "%s not allowed in pipeline mode",
-						  "PQsendQuery");
+								"PQsendQuery");
 		return 0;
 	}
 
@@ -1512,7 +1512,7 @@ PQsendQueryParams(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1558,7 +1558,7 @@ PQsendPrepare(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1652,7 +1652,7 @@ PQsendQueryPrepared(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -2099,10 +2099,9 @@ PQgetResult(PGconn *conn)
 
 			/*
 			 * We're about to return the NULL that terminates the round of
-			 * results from the current query; prepare to send the results
-			 * of the next query, if any, when we're called next.  If there's
-			 * no next element in the command queue, this gets us in IDLE
-			 * state.
+			 * results from the current query; prepare to send the results of
+			 * the next query, if any, when we're called next.  If there's no
+			 * next element in the command queue, this gets us in IDLE state.
 			 */
 			pqPipelineProcessQueue(conn);
 			res = NULL;			/* query is complete */
@@ -3047,6 +3046,7 @@ pqPipelineProcessQueue(PGconn *conn)
 			return;
 
 		case PGASYNC_IDLE:
+
 			/*
 			 * If we're in IDLE mode and there's some command in the queue,
 			 * get us into PIPELINE_IDLE mode and process normally.  Otherwise
diff --git a/src/interfaces/libpq/fe-lobj.c b/src/interfaces/libpq/fe-lobj.c
index 4cb6a468597..206266fd043 100644
--- a/src/interfaces/libpq/fe-lobj.c
+++ b/src/interfaces/libpq/fe-lobj.c
@@ -142,7 +142,7 @@ lo_truncate(PGconn *conn, int fd, size_t len)
 	if (conn->lobjfuncs->fn_lo_truncate == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate");
+								"lo_truncate");
 		return -1;
 	}
 
@@ -205,7 +205,7 @@ lo_truncate64(PGconn *conn, int fd, pg_int64 len)
 	if (conn->lobjfuncs->fn_lo_truncate64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate64");
+								"lo_truncate64");
 		return -1;
 	}
 
@@ -395,7 +395,7 @@ lo_lseek64(PGconn *conn, int fd, pg_int64 offset, int whence)
 	if (conn->lobjfuncs->fn_lo_lseek64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek64");
+								"lo_lseek64");
 		return -1;
 	}
 
@@ -485,7 +485,7 @@ lo_create(PGconn *conn, Oid lobjId)
 	if (conn->lobjfuncs->fn_lo_create == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_create");
+								"lo_create");
 		return InvalidOid;
 	}
 
@@ -558,7 +558,7 @@ lo_tell64(PGconn *conn, int fd)
 	if (conn->lobjfuncs->fn_lo_tell64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell64");
+								"lo_tell64");
 		return -1;
 	}
 
@@ -667,7 +667,7 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 	if (fd < 0)
 	{							/* error */
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -723,8 +723,8 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not read from file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -778,8 +778,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -799,8 +799,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 			/* deliberately overwrite any error from lo_close */
 			pqClearConnErrorState(conn);
 			libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-							  filename,
-							  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+									filename,
+									strerror_r(save_errno, sebuf, sizeof(sebuf)));
 			return -1;
 		}
 	}
@@ -822,7 +822,7 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 	if (close(fd) != 0 && result >= 0)
 	{
 		libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		result = -1;
 	}
 
@@ -954,56 +954,56 @@ lo_initialize(PGconn *conn)
 	if (lobjfuncs->fn_lo_open == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_open");
+								"lo_open");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_close == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_close");
+								"lo_close");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_creat == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_creat");
+								"lo_creat");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_unlink == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_unlink");
+								"lo_unlink");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_lseek == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek");
+								"lo_lseek");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_tell == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell");
+								"lo_tell");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_read == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "loread");
+								"loread");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_write == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lowrite");
+								"lowrite");
 		free(lobjfuncs);
 		return -1;
 	}
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 3653a1a8a62..660cdec93c9 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -749,8 +749,8 @@ retry4:
 	 */
 definitelyEOF:
 	libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-					   "\tThis probably means the server terminated abnormally\n"
-					   "\tbefore or while processing the request.");
+							"\tThis probably means the server terminated abnormally\n"
+							"\tbefore or while processing the request.");
 
 	/* Come here if lower-level code already set a suitable errorMessage */
 definitelyFailed:
@@ -1067,7 +1067,7 @@ pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s() failed: %s", "select",
-						  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 	}
 
 	return result;
@@ -1280,7 +1280,7 @@ libpq_ngettext(const char *msgid, const char *msgid_plural, unsigned long n)
  * newline.
  */
 void
-libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
+libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
@@ -1309,7 +1309,7 @@ libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
  * format should not end with a newline.
  */
 void
-libpq_append_conn_error(PGconn *conn, const char *fmt, ...)
+libpq_append_conn_error(PGconn *conn, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index 8ab6a884165..b79d74f7489 100644
--- a/src/interfaces/libpq/fe-protocol3.c
+++ b/src/interfaces/libpq/fe-protocol3.c
@@ -466,7 +466,7 @@ static void
 handleSyncLoss(PGconn *conn, char id, int msgLength)
 {
 	libpq_append_conn_error(conn, "lost synchronization with server: got message type \"%c\", length %d",
-					  id, msgLength);
+							id, msgLength);
 	/* build an error result holding the error message */
 	pqSaveErrorResult(conn);
 	conn->asyncStatus = PGASYNC_READY;	/* drop out of PQgetResult wait loop */
diff --git a/src/interfaces/libpq/fe-secure-common.c b/src/interfaces/libpq/fe-secure-common.c
index de115b37649..3ecc7bf6159 100644
--- a/src/interfaces/libpq/fe-secure-common.c
+++ b/src/interfaces/libpq/fe-secure-common.c
@@ -226,7 +226,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 		 * wrong given the subject matter.
 		 */
 		libpq_append_conn_error(conn, "certificate contains IP address with invalid length %zu",
-						  iplen);
+								iplen);
 		return -1;
 	}
 
@@ -235,7 +235,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 	if (!addrstr)
 	{
 		libpq_append_conn_error(conn, "could not convert certificate's IP address to string: %s",
-						  strerror_r(errno, sebuf, sizeof(sebuf)));
+								strerror_r(errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -292,7 +292,7 @@ pq_verify_peer_name_matches_certificate(PGconn *conn)
 		else if (names_examined == 1)
 		{
 			libpq_append_conn_error(conn, "server certificate for \"%s\" does not match host name \"%s\"",
-							  first_name, host);
+									first_name, host);
 		}
 		else
 		{
diff --git a/src/interfaces/libpq/fe-secure-gssapi.c b/src/interfaces/libpq/fe-secure-gssapi.c
index 038e847b7e9..0af4de941af 100644
--- a/src/interfaces/libpq/fe-secure-gssapi.c
+++ b/src/interfaces/libpq/fe-secure-gssapi.c
@@ -213,8 +213,8 @@ pg_GSS_write(PGconn *conn, const void *ptr, size_t len)
 		if (output.length > PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "client tried to send oversize GSSAPI packet (%zu > %zu)",
-							  (size_t) output.length,
-							  PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
+									(size_t) output.length,
+									PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			goto cleanup;
 		}
@@ -349,8 +349,8 @@ pg_GSS_read(PGconn *conn, void *ptr, size_t len)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			return -1;
 		}
@@ -590,8 +590,8 @@ pqsecure_open_gss(PGconn *conn)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			return PGRES_POLLING_FAILED;
 		}
 
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index 6a4431ddfe9..e6da377fb9d 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -213,12 +213,12 @@ rloop:
 				if (result_errno == EPIPE ||
 					result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -313,12 +313,12 @@ pgtls_write(PGconn *conn, const void *ptr, size_t len)
 				result_errno = SOCK_ERRNO;
 				if (result_errno == EPIPE || result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -415,7 +415,7 @@ pgtls_get_peer_certificate_hash(PGconn *conn, size_t *len)
 			if (algo_type == NULL)
 			{
 				libpq_append_conn_error(conn, "could not find digest for NID %s",
-								  OBJ_nid2sn(algo_nid));
+										OBJ_nid2sn(algo_nid));
 				return NULL;
 			}
 			break;
@@ -967,7 +967,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_min_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for minimum SSL protocol version",
-							  conn->ssl_min_protocol_version);
+									conn->ssl_min_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -993,7 +993,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_max_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for maximum SSL protocol version",
-							  conn->ssl_max_protocol_version);
+									conn->ssl_max_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1037,7 +1037,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read root certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1089,10 +1089,10 @@ initialize_SSL(PGconn *conn)
 			 */
 			if (fnbuf[0] == '\0')
 				libpq_append_conn_error(conn, "could not get home directory to locate root certificate file\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.");
+										"Either provide the file or change sslmode to disable server certificate verification.");
 			else
 				libpq_append_conn_error(conn, "root certificate file \"%s\" does not exist\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
+										"Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1122,7 +1122,7 @@ initialize_SSL(PGconn *conn)
 		if (errno != ENOENT && errno != ENOTDIR)
 		{
 			libpq_append_conn_error(conn, "could not open certificate file \"%s\": %s",
-							  fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
+									fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1140,7 +1140,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1239,7 +1239,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				free(engine_str);
 				return -1;
@@ -1250,7 +1250,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not initialize SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				ENGINE_free(conn->engine);
 				conn->engine = NULL;
@@ -1265,7 +1265,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not read private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1278,7 +1278,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1315,10 +1315,10 @@ initialize_SSL(PGconn *conn)
 		{
 			if (errno == ENOENT)
 				libpq_append_conn_error(conn, "certificate present, but not private key file \"%s\"",
-								  fnbuf);
+										fnbuf);
 			else
 				libpq_append_conn_error(conn, "could not stat private key file \"%s\": %m",
-								  fnbuf);
+										fnbuf);
 			return -1;
 		}
 
@@ -1326,7 +1326,7 @@ initialize_SSL(PGconn *conn)
 		if (!S_ISREG(buf.st_mode))
 		{
 			libpq_append_conn_error(conn, "private key file \"%s\" is not a regular file",
-							  fnbuf);
+									fnbuf);
 			return -1;
 		}
 
@@ -1383,7 +1383,7 @@ initialize_SSL(PGconn *conn)
 			if (SSL_use_PrivateKey_file(conn->ssl, fnbuf, SSL_FILETYPE_ASN1) != 1)
 			{
 				libpq_append_conn_error(conn, "could not load private key file \"%s\": %s",
-								  fnbuf, err);
+										fnbuf, err);
 				SSLerrfree(err);
 				return -1;
 			}
@@ -1399,7 +1399,7 @@ initialize_SSL(PGconn *conn)
 		char	   *err = SSLerrmessage(ERR_get_error());
 
 		libpq_append_conn_error(conn, "certificate does not match private key file \"%s\": %s",
-						  fnbuf, err);
+								fnbuf, err);
 		SSLerrfree(err);
 		return -1;
 	}
@@ -1452,7 +1452,7 @@ open_client_SSL(PGconn *conn)
 
 					if (r == -1)
 						libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-										  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					else
 						libpq_append_conn_error(conn, "SSL SYSCALL error: EOF detected");
 					pgtls_close(conn);
@@ -1494,12 +1494,12 @@ open_client_SSL(PGconn *conn)
 						case SSL_R_VERSION_TOO_LOW:
 #endif
 							libpq_append_conn_error(conn, "This may indicate that the server does not support any SSL protocol version between %s and %s.",
-											  conn->ssl_min_protocol_version ?
-											  conn->ssl_min_protocol_version :
-											  MIN_OPENSSL_TLS_VERSION,
-											  conn->ssl_max_protocol_version ?
-											  conn->ssl_max_protocol_version :
-											  MAX_OPENSSL_TLS_VERSION);
+													conn->ssl_min_protocol_version ?
+													conn->ssl_min_protocol_version :
+													MIN_OPENSSL_TLS_VERSION,
+													conn->ssl_max_protocol_version ?
+													conn->ssl_max_protocol_version :
+													MAX_OPENSSL_TLS_VERSION);
 							break;
 						default:
 							break;
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index 66e401bf3d9..8069e381424 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -255,14 +255,14 @@ pqsecure_raw_read(PGconn *conn, void *ptr, size_t len)
 			case EPIPE:
 			case ECONNRESET:
 				libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-								   "\tThis probably means the server terminated abnormally\n"
-								   "\tbefore or while processing the request.");
+										"\tThis probably means the server terminated abnormally\n"
+										"\tbefore or while processing the request.");
 				break;
 
 			default:
 				libpq_append_conn_error(conn, "could not receive data from server: %s",
-								  SOCK_STRERROR(result_errno,
-												sebuf, sizeof(sebuf)));
+										SOCK_STRERROR(result_errno,
+													  sebuf, sizeof(sebuf)));
 				break;
 		}
 	}
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 1dc264fe544..8890525cdf4 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -897,8 +897,8 @@ extern char *libpq_ngettext(const char *msgid, const char *msgid_plural, unsigne
  */
 #undef _
 
-extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...) pg_attribute_printf(2, 3);
-extern void libpq_append_conn_error(PGconn *conn, const char *fmt, ...) pg_attribute_printf(2, 3);
+extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...) pg_attribute_printf(2, 3);
+extern void libpq_append_conn_error(PGconn *conn, const char *fmt,...) pg_attribute_printf(2, 3);
 
 /*
  * These macros are needed to let error-handling code be portable between
-- 
2.34.1

From a0004b27974acee0fd52476f50ca71bb7f5bba25 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Fri, 3 Mar 2023 15:27:21 +0100
Subject: [PATCH v12 4/4] Remove unnecessary check from Fisher-Yates
 implementation

Andrey Borodin pointed out that the "undefined data check" was
unnecessary for Fisher-Yates implementations when the data that was
fetched was known to be initialized. There was one such place in the
codebase, so this removes the check there.
---
 src/backend/optimizer/geqo/geqo_recombination.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/backend/optimizer/geqo/geqo_recombination.c b/src/backend/optimizer/geqo/geqo_recombination.c
index a5d3e47ad11..53bf0cc0a42 100644
--- a/src/backend/optimizer/geqo/geqo_recombination.c
+++ b/src/backend/optimizer/geqo/geqo_recombination.c
@@ -51,9 +51,7 @@ init_tour(PlannerInfo *root, Gene *tour, int num_gene)
 	for (i = 1; i < num_gene; i++)
 	{
 		j = geqo_randint(root, i, 0);
-		/* i != j check avoids fetching uninitialized array element */
-		if (i != j)
-			tour[i] = tour[j];
+		tour[i] = tour[j];
 		tour[j] = (Gene) (i + 1);
 	}
 }
-- 
2.34.1

From efcab3b8e9c09652acd6bcf3d5247a8a8393c08b Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Fri, 3 Mar 2023 15:27:21 +0100
Subject: [PATCH v13 5/5] Remove unnecessary check from Fisher-Yates
 implementation

Andrey Borodin pointed out that the "undefined data check" was
unnecessary for Fisher-Yates implementations when the data that was
fetched was known to be initialized. There was one such place in the
codebase, so this removes the check there.
---
 src/backend/optimizer/geqo/geqo_recombination.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/backend/optimizer/geqo/geqo_recombination.c b/src/backend/optimizer/geqo/geqo_recombination.c
index a5d3e47ad11..53bf0cc0a42 100644
--- a/src/backend/optimizer/geqo/geqo_recombination.c
+++ b/src/backend/optimizer/geqo/geqo_recombination.c
@@ -51,9 +51,7 @@ init_tour(PlannerInfo *root, Gene *tour, int num_gene)
 	for (i = 1; i < num_gene; i++)
 	{
 		j = geqo_randint(root, i, 0);
-		/* i != j check avoids fetching uninitialized array element */
-		if (i != j)
-			tour[i] = tour[j];
+		tour[i] = tour[j];
 		tour[j] = (Gene) (i + 1);
 	}
 }
-- 
2.34.1

From 0e711b963bfec4e3a591f8f58519bb6d5be5f02a Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 25 Jan 2023 10:22:41 +0100
Subject: [PATCH v13 2/5] Refactor libpq to store addrinfo in a libpq owned
 array

This refactors libpq to copy addrinfos returned by getaddrinfo to
memory owned by us. This refactoring is useful for two upcoming patches,
which need to change the addrinfo list in some way. Doing that with the
original addrinfo list is risky since we don't control how memory is
freed. Also changing the contents of a C array is quite a bit easier
than changing a linked list.

As a nice side effect of this refactor the is that mechanism for
iteration over addresses in PQconnectPoll is now identical to its
iteration over hosts.
---
 src/include/libpq/pqcomm.h        |   6 ++
 src/interfaces/libpq/fe-connect.c | 107 +++++++++++++++++++++---------
 src/interfaces/libpq/libpq-int.h  |   7 +-
 src/tools/pgindent/typedefs.list  |   1 +
 4 files changed, 87 insertions(+), 34 deletions(-)

diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index 5268d442abe..507ee825824 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+} AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index dd4b98e0998..b085892feac 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -383,6 +383,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *connstr,
@@ -2246,7 +2247,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2290,11 +2291,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2441,9 +2442,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2456,6 +2457,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2496,7 +2498,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2519,8 +2521,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
 											ch->host, gai_strerror(ret));
@@ -2531,8 +2533,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
 											ch->hostaddr, gai_strerror(ret));
@@ -2541,7 +2543,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2556,8 +2558,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
 											portstr, gai_strerror(ret));
@@ -2566,8 +2568,14 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		if (!store_conn_addrinfo(conn, addrlist))
+		{
+			pg_freeaddrinfo_all(hint.ai_family, addrlist);
+			libpq_append_conn_error(conn, "out of memory");
+			goto error_return;
+		}
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2624,30 +2632,29 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2663,7 +2670,7 @@ keep_going:						/* We will come back to here until there is
 						conn->connip = strdup(host_addr);
 
 					/* Try to create the socket */
-					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
+					conn->sock = socket(addr_cur->family, SOCK_STREAM, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2674,7 +2681,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2700,7 +2707,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2727,7 +2734,7 @@ keep_going:						/* We will come back to here until there is
 					}
 #endif							/* F_SETFD */
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2819,8 +2826,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4243,6 +4250,45 @@ freePGconn(PGconn *conn)
 	free(conn);
 }
 
+/*
+ * Copies over the addrinfos from addrlist to the PGconn. The reason we do this
+ * so that we can edit the resulting list as we please, because now the memory
+ * is owned by us. Changing the original addrinfo directly is risky, since we
+ * don't control how the memory is freed and by changing it we might confuse
+ * the implementation of freeaddrinfo.
+ */
+static bool
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+		return false;
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	return true;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4250,11 +4296,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 8890525cdf4..8f96c52e6c3 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -470,9 +470,10 @@ struct pg_conn
 	PGTargetServerType target_server_type;	/* desired session properties */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
-	int			addrlist_family;	/* needed to know how to free addrlist */
+	int			naddr;			/* number of addresses returned by getaddrinfo */
+	int			whichaddr;		/* the address currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	bool		send_appname;	/* okay to send application_name? */
 
 	/* Miscellaneous stuff */
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 097f42e1b34..5c5aa8bf4c9 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -26,6 +26,7 @@ AcquireSampleRowsFunc
 ActionList
 ActiveSnapshotElt
 AddForeignUpdateTargets_function
+AddrInfo
 AffixNode
 AffixNodeData
 AfterTriggerEvent
-- 
2.34.1

From e63f83896fce4ae2068071e8aa50b18ffa8a595d Mon Sep 17 00:00:00 2001
From: Jelte Fennema <github-tech@jeltef.nl>
Date: Mon, 12 Sep 2022 09:44:06 +0200
Subject: [PATCH v13 3/5] Support load balancing in libpq

This adds support for load balancing to libpq using the newly added
load_balance_hosts parameter. When setting the load_balance_hosts
parameter to random, hosts and addresses will be connected to in a
random order. This then results in load balancing across these
hosts/addresses if multiple clients do this at the same time.

This patch implements two levels of random load balancing:
1. The given hosts are randomly shuffled, before resolving them
    one-by-one.
2. Once a host its addresses get resolved, those addresses are shuffled,
    before trying to connect to them one-by-one.
---
 doc/src/sgml/libpq.sgml                       |  74 ++++++++++++
 src/interfaces/libpq/fe-connect.c             | 105 ++++++++++++++++++
 src/interfaces/libpq/libpq-int.h              |  17 ++-
 src/interfaces/libpq/meson.build              |   2 +
 .../libpq/t/003_load_balance_host_list.pl     |  82 ++++++++++++++
 src/test/perl/PostgreSQL/Test/Cluster.pm      |  16 +++
 src/tools/pgindent/typedefs.list              |   1 +
 7 files changed, 296 insertions(+), 1 deletion(-)
 create mode 100644 src/interfaces/libpq/t/003_load_balance_host_list.pl

diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 3706d349abc..0ada127a73b 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -2069,6 +2069,80 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="libpq-connect-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls the order in which the client tries to connect to the available
+        hosts and addresses. Once a connection attempt is successful no other
+        hosts and addresses will be tried. This parameter is typically used in
+        combination with multiple host names or a DNS record that returns
+        multiple IPs. This parameter can be used in combination with
+        <xref linkend="libpq-connect-target-session-attrs"/>
+        to, for example, load balance over standby servers only. Once successfully
+        connected, subsequent queries on the returned connection will all be
+        sent to the same server. There are currently two modes:
+        <variablelist>
+         <varlistentry>
+          <term><literal>disable</literal> (default)</term>
+          <listitem>
+           <para>
+            No load balancing across hosts is performed. The order in which
+            hosts and addresses are tried is the same for every connection
+            attempt: Hosts are tried in the order in which they are provided and
+            addresses are tried in the order they are received from DNS or a
+            hosts file.
+           </para>
+
+           <para>
+            While this may sound similar to round-robin load balancing, it is
+            not. Round-robin load balancing requires that subsequent connection
+            attempts start iterating over hosts where the previous connection
+            attempt stopped. This is not done when using <literal>disable</literal>.
+            Instead every connection attempt starts at <emphasis>the same</emphasis>
+            first host. So, if that host is online and accepting connections, all
+            clients will connect to it and all of the other hosts in the
+            list get no connections at all.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>random</literal></term>
+          <listitem>
+           <para>
+            Hosts and addresses are tried in random order. This value is mostly
+            useful when opening multiple connections at the same time, possibly
+            from different machines. This way connections can be load balanced
+            across multiple <productname>PostgreSQL</productname> servers.
+           </para>
+           <para>
+            While random load balancing, due to its random nature, will almost
+            never result in a completely uniform distribution, it statistically
+            gets quite close. One important aspect here is that this algorithm
+            uses two levels of random choices: First the hosts
+            will be resolved in random order. Then secondly, before resolving
+            the next host, all resolved addresses for the current host will be
+            tried in random order. This behaviour can skew the amount of
+            connections each node gets greatly in certain cases, for instance
+            when some hosts resolve to more addresses than others. But such a
+            skew can also be used on purpose, e.g. to increase the number of
+            connections a larger server gets by providing its hostname multiple
+            times in the host string.
+           </para>
+           <para>
+            When using this value it's recommended to also configure a reasonable
+            value for <xref linkend="libpq-connect-connect-timeout"/>. Because then,
+            if one of the nodes that are used for load balancing is not responding,
+            a new node will be tried.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
    </para>
   </sect2>
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index b085892feac..c180ebb26d1 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -123,6 +123,7 @@ static int	ldapServiceLookup(const char *purl, PQconninfoOption *options,
 #define DefaultChannelBinding	"disable"
 #endif
 #define DefaultTargetSessionAttrs	"any"
+#define DefaultLoadBalanceHosts	"disable"
 #ifdef USE_SSL
 #define DefaultSSLMode "prefer"
 #else
@@ -345,6 +346,11 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Target-Session-Attrs", "", 15, /* sizeof("prefer-standby") = 15 */
 	offsetof(struct pg_conn, target_session_attrs)},
 
+	{"load_balance_hosts", "PGLOADBALANCEHOSTS",
+		DefaultLoadBalanceHosts, NULL,
+		"Load-Balance-Hosts", "", 8,	/* sizeof("disable") = 8 */
+	offsetof(struct pg_conn, load_balance_hosts)},
+
 	/* Terminating entry --- MUST BE LAST */
 	{NULL, NULL, NULL, NULL,
 	NULL, NULL, 0}
@@ -429,6 +435,8 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static bool parse_int_param(const char *value, int *result, PGconn *conn,
+							const char *context);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1013,6 +1021,32 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on the connection address,
+ * timestamp and PID.
+ */
+static bool
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		struct timeval tval = {0};
+
+		gettimeofday(&tval, NULL);
+
+		rseed = ((uint64) conn) ^
+			((uint64) getpid()) ^
+			((uint64) tval.tv_usec) ^
+			((uint64) tval.tv_sec);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	return true;
+}
+
 /*
  *		connectOptions2
  *
@@ -1570,6 +1604,50 @@ connectOptions2(PGconn *conn)
 	else
 		conn->target_server_type = SERVER_TYPE_ANY;
 
+	/*
+	 * validate load_balance_hosts option, and set load_balance_type
+	 */
+	if (conn->load_balance_hosts)
+	{
+		if (strcmp(conn->load_balance_hosts, "disable") == 0)
+			conn->load_balance_type = LOAD_BALANCE_DISABLE;
+		else if (strcmp(conn->load_balance_hosts, "random") == 0)
+			conn->load_balance_type = LOAD_BALANCE_RANDOM;
+		else
+		{
+			conn->status = CONNECTION_BAD;
+			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
+									"load_balance_hosts",
+									conn->load_balance_hosts);
+			return false;
+		}
+	}
+	else
+		conn->load_balance_type = LOAD_BALANCE_DISABLE;
+
+	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+	{
+		if (!libpq_prng_init(conn))
+			return false;
+
+		/*
+		 * This is the "inside-out" variant of the Fisher-Yates shuffle
+		 * algorithm. Notionally, we append each new value to the array and
+		 * then swap it with a randomly-chosen array element (possibly
+		 * including itself, else we fail to generate permutations with the
+		 * last integer last).  The swap step can be optimized by combining it
+		 * with the insertion.
+		 */
+		for (i = 1; i < conn->nconnhost; i++)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
 	/*
 	 * Resolve special "auto" client_encoding from the locale
 	 */
@@ -2576,6 +2654,32 @@ keep_going:						/* We will come back to here until there is
 		}
 		pg_freeaddrinfo_all(hint.ai_family, addrlist);
 
+		/*
+		 * If random load balancing is enabled we shuffle the addresses.
+		 */
+		if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+		{
+			/*
+			 * This is the "inside-out" variant of the Fisher-Yates shuffle
+			 * algorithm. Notionally, we append each new value to the array
+			 * and then swap it with a randomly-chosen array element (possibly
+			 * including itself, else we fail to generate permutations with
+			 * the last integer last).  The swap step can be optimized by
+			 * combining it with the insertion.
+			 *
+			 * We don't need to initialize conn->prng_state here, because that
+			 * already happened in connectOptions2.
+			 */
+			for (int i = 1; i < conn->naddr; i++)
+			{
+				int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+				AddrInfo	temp = conn->addr[j];
+
+				conn->addr[j] = conn->addr[i];
+				conn->addr[i] = temp;
+			}
+		}
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -4244,6 +4348,7 @@ freePGconn(PGconn *conn)
 	free(conn->outBuffer);
 	free(conn->rowBuf);
 	free(conn->target_session_attrs);
+	free(conn->load_balance_hosts);
 	termPQExpBuffer(&conn->errorMessage);
 	termPQExpBuffer(&conn->workBuffer);
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 8f96c52e6c3..ff79396c0be 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -26,7 +26,8 @@
 #include <netdb.h>
 #include <sys/socket.h>
 #include <time.h>
-#ifndef WIN32
+/* MinGW has sys/time.h, but MSVC doesn't */
+#ifndef _MSC_VER
 #include <sys/time.h>
 #endif
 
@@ -82,6 +83,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -242,6 +245,13 @@ typedef enum
 	SERVER_TYPE_PREFER_STANDBY_PASS2	/* second pass - behaves same as ANY */
 } PGTargetServerType;
 
+/* Target server type (decoded value of load_balance_hosts) */
+typedef enum
+{
+	LOAD_BALANCE_DISABLE = 0,	/* Use the existing host order (default) */
+	LOAD_BALANCE_RANDOM,		/* Randomly shuffle the hosts */
+} PGLoadBalanceType;
+
 /* Boolean value plus a not-known state, for GUCs we might have to fetch */
 typedef enum
 {
@@ -397,6 +407,7 @@ struct pg_conn
 	char	   *ssl_max_protocol_version;	/* maximum TLS protocol version */
 	char	   *target_session_attrs;	/* desired session properties */
 	char	   *require_auth;	/* name of the expected auth method */
+	char	   *load_balance_hosts; /* load balance over hosts */
 
 	/* Optional file to write trace info to */
 	FILE	   *Pfdebug;
@@ -468,6 +479,8 @@ struct pg_conn
 
 	/* Transient state needed while establishing connection */
 	PGTargetServerType target_server_type;	/* desired session properties */
+	PGLoadBalanceType load_balance_type;	/* desired load balancing
+											 * algorithm */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
 	int			naddr;			/* number of addresses returned by getaddrinfo */
@@ -487,6 +500,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index 3cd0ddb4945..80e6a15adf8 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -116,6 +116,8 @@ tests += {
     'tests': [
       't/001_uri.pl',
       't/002_api.pl',
+      't/003_load_balance_host_list.pl',
+      't/004_load_balance_dns.pl',
     ],
     'env': {'with_ssl': ssl_library},
   },
diff --git a/src/interfaces/libpq/t/003_load_balance_host_list.pl b/src/interfaces/libpq/t/003_load_balance_host_list.pl
new file mode 100644
index 00000000000..1bdddfdbcfd
--- /dev/null
+++ b/src/interfaces/libpq/t/003_load_balance_host_list.pl
@@ -0,0 +1,82 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests load balancing across the list of different hosts in the host
+# parameter of the connection string.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $node1 = PostgreSQL::Test::Cluster->new('node1');
+my $node2 = PostgreSQL::Test::Cluster->new('node2', own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# Start the tests for load balancing method 1
+my $hostlist = $node1->host . ',' . $node2->host . ',' . $node3->host;
+my $portlist = $node1->port . ',' . $node2->port . ',' . $node3->port;
+
+$node1->connect_fails(
+	"host=$hostlist port=$portlist load_balance_hosts=doesnotexist",
+	"load_balance_hosts doesn't accept unknown values",
+	expected_stderr => qr/invalid load_balance_hosts value: "doesnotexist"/);
+
+# load_balance_hosts=disable should always choose the first one.
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=disable",
+	"load_balance_hosts=disable connects to the first node",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+# Statistically the following loop with load_balance_hosts=random will almost
+# certainly connect at least once to each of the nodes. The chance of that not
+# happening is so small that it's negligible: (2/3)^50 = 1.56832855e-9
+foreach my $i (1 .. 50) {
+	$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random",
+		"seed 1234 selects node 1 first",
+		sql => "SELECT 'connect1'");
+}
+
+my $node1_occurences = () = $node1->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node2_occurences = () = $node2->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node3_occurences = () = $node3->log_content() =~ /statement: SELECT 'connect1'/g;
+
+my $total_occurences = $node1_occurences + $node2_occurences + $node3_occurences;
+
+ok($node1_occurences > 1, "expected at least one execution on node1, found $node1_occurences");
+ok($node2_occurences > 1, "expected at least one execution on node2, found $node2_occurences");
+ok($node3_occurences > 1, "expected at least one execution on node3, found $node3_occurences");
+ok($total_occurences == 50, "expected 50 executions across all nodes, found $total_occurences");
+
+$node1->stop();
+$node2->stop();
+
+# load_balance_hosts=disable should continue trying hosts until it finds a
+# working one.
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=disable",
+	"load_balance_hosts=disable continues until it connects to the a working node",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+# Also with load_balance_hosts=random we continue to the next nodes if previous
+# ones are down. Connect a few times to make sure it's not just lucky.
+foreach my $i (1 .. 5) {
+	$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random",
+		"load_balance_hosts=random continues until it connects to the a working node",
+		sql => "SELECT 'connect4'",
+		log_like => [qr/statement: SELECT 'connect4'/]);
+}
+
+done_testing();
+
diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 3e2a27fb717..a3aef8b5e91 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -2567,6 +2567,22 @@ sub issues_sql_like
 	return;
 }
 
+=pod
+
+=item $node->log_content()
+
+Returns the contents of log of the node
+
+=cut
+
+sub log_content
+{
+	my ($self) = @_;
+	return
+	  PostgreSQL::Test::Utils::slurp_file($self->logfile);
+}
+
+
 =pod
 
 =item $node->run_log(...)
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 5c5aa8bf4c9..2571d22f96d 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1702,6 +1702,7 @@ PGFileType
 PGFunction
 PGLZ_HistEntry
 PGLZ_Strategy
+PGLoadBalanceType
 PGMessageField
 PGModuleMagicFunction
 PGNoticeHooks
-- 
2.34.1

From 15ad55b31ca45114086c7ed54886056f810b7995 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 30 Nov 2022 10:07:19 +0100
Subject: [PATCH v13 1/5] libpq: Run pgindent after a9e9a9f32b3

It seems that pgindent was not run after the error handling refactor in
commit a9e9a9f32b35edf129c88e8b929ef223f8511f59. This fixes that and
also addresses a few other things pgindent wanted to change in libpq.
---
 src/interfaces/libpq/fe-exec.c           | 16 +++---
 src/interfaces/libpq/fe-lobj.c           | 42 ++++++++--------
 src/interfaces/libpq/fe-misc.c           | 10 ++--
 src/interfaces/libpq/fe-protocol3.c      |  2 +-
 src/interfaces/libpq/fe-secure-common.c  |  6 +--
 src/interfaces/libpq/fe-secure-gssapi.c  | 12 ++---
 src/interfaces/libpq/fe-secure-openssl.c | 64 ++++++++++++------------
 src/interfaces/libpq/fe-secure.c         |  8 +--
 src/interfaces/libpq/libpq-int.h         |  4 +-
 9 files changed, 82 insertions(+), 82 deletions(-)

diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index ec62550e385..0c2dae6ed9e 100644
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -1444,7 +1444,7 @@ PQsendQueryInternal(PGconn *conn, const char *query, bool newQuery)
 	if (conn->pipelineStatus != PQ_PIPELINE_OFF)
 	{
 		libpq_append_conn_error(conn, "%s not allowed in pipeline mode",
-						  "PQsendQuery");
+								"PQsendQuery");
 		return 0;
 	}
 
@@ -1512,7 +1512,7 @@ PQsendQueryParams(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1558,7 +1558,7 @@ PQsendPrepare(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1652,7 +1652,7 @@ PQsendQueryPrepared(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -2099,10 +2099,9 @@ PQgetResult(PGconn *conn)
 
 			/*
 			 * We're about to return the NULL that terminates the round of
-			 * results from the current query; prepare to send the results
-			 * of the next query, if any, when we're called next.  If there's
-			 * no next element in the command queue, this gets us in IDLE
-			 * state.
+			 * results from the current query; prepare to send the results of
+			 * the next query, if any, when we're called next.  If there's no
+			 * next element in the command queue, this gets us in IDLE state.
 			 */
 			pqPipelineProcessQueue(conn);
 			res = NULL;			/* query is complete */
@@ -3047,6 +3046,7 @@ pqPipelineProcessQueue(PGconn *conn)
 			return;
 
 		case PGASYNC_IDLE:
+
 			/*
 			 * If we're in IDLE mode and there's some command in the queue,
 			 * get us into PIPELINE_IDLE mode and process normally.  Otherwise
diff --git a/src/interfaces/libpq/fe-lobj.c b/src/interfaces/libpq/fe-lobj.c
index 4cb6a468597..206266fd043 100644
--- a/src/interfaces/libpq/fe-lobj.c
+++ b/src/interfaces/libpq/fe-lobj.c
@@ -142,7 +142,7 @@ lo_truncate(PGconn *conn, int fd, size_t len)
 	if (conn->lobjfuncs->fn_lo_truncate == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate");
+								"lo_truncate");
 		return -1;
 	}
 
@@ -205,7 +205,7 @@ lo_truncate64(PGconn *conn, int fd, pg_int64 len)
 	if (conn->lobjfuncs->fn_lo_truncate64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate64");
+								"lo_truncate64");
 		return -1;
 	}
 
@@ -395,7 +395,7 @@ lo_lseek64(PGconn *conn, int fd, pg_int64 offset, int whence)
 	if (conn->lobjfuncs->fn_lo_lseek64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek64");
+								"lo_lseek64");
 		return -1;
 	}
 
@@ -485,7 +485,7 @@ lo_create(PGconn *conn, Oid lobjId)
 	if (conn->lobjfuncs->fn_lo_create == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_create");
+								"lo_create");
 		return InvalidOid;
 	}
 
@@ -558,7 +558,7 @@ lo_tell64(PGconn *conn, int fd)
 	if (conn->lobjfuncs->fn_lo_tell64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell64");
+								"lo_tell64");
 		return -1;
 	}
 
@@ -667,7 +667,7 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 	if (fd < 0)
 	{							/* error */
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -723,8 +723,8 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not read from file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -778,8 +778,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -799,8 +799,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 			/* deliberately overwrite any error from lo_close */
 			pqClearConnErrorState(conn);
 			libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-							  filename,
-							  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+									filename,
+									strerror_r(save_errno, sebuf, sizeof(sebuf)));
 			return -1;
 		}
 	}
@@ -822,7 +822,7 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 	if (close(fd) != 0 && result >= 0)
 	{
 		libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		result = -1;
 	}
 
@@ -954,56 +954,56 @@ lo_initialize(PGconn *conn)
 	if (lobjfuncs->fn_lo_open == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_open");
+								"lo_open");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_close == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_close");
+								"lo_close");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_creat == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_creat");
+								"lo_creat");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_unlink == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_unlink");
+								"lo_unlink");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_lseek == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek");
+								"lo_lseek");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_tell == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell");
+								"lo_tell");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_read == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "loread");
+								"loread");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_write == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lowrite");
+								"lowrite");
 		free(lobjfuncs);
 		return -1;
 	}
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 3653a1a8a62..660cdec93c9 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -749,8 +749,8 @@ retry4:
 	 */
 definitelyEOF:
 	libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-					   "\tThis probably means the server terminated abnormally\n"
-					   "\tbefore or while processing the request.");
+							"\tThis probably means the server terminated abnormally\n"
+							"\tbefore or while processing the request.");
 
 	/* Come here if lower-level code already set a suitable errorMessage */
 definitelyFailed:
@@ -1067,7 +1067,7 @@ pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s() failed: %s", "select",
-						  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 	}
 
 	return result;
@@ -1280,7 +1280,7 @@ libpq_ngettext(const char *msgid, const char *msgid_plural, unsigned long n)
  * newline.
  */
 void
-libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
+libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
@@ -1309,7 +1309,7 @@ libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
  * format should not end with a newline.
  */
 void
-libpq_append_conn_error(PGconn *conn, const char *fmt, ...)
+libpq_append_conn_error(PGconn *conn, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index 8ab6a884165..b79d74f7489 100644
--- a/src/interfaces/libpq/fe-protocol3.c
+++ b/src/interfaces/libpq/fe-protocol3.c
@@ -466,7 +466,7 @@ static void
 handleSyncLoss(PGconn *conn, char id, int msgLength)
 {
 	libpq_append_conn_error(conn, "lost synchronization with server: got message type \"%c\", length %d",
-					  id, msgLength);
+							id, msgLength);
 	/* build an error result holding the error message */
 	pqSaveErrorResult(conn);
 	conn->asyncStatus = PGASYNC_READY;	/* drop out of PQgetResult wait loop */
diff --git a/src/interfaces/libpq/fe-secure-common.c b/src/interfaces/libpq/fe-secure-common.c
index de115b37649..3ecc7bf6159 100644
--- a/src/interfaces/libpq/fe-secure-common.c
+++ b/src/interfaces/libpq/fe-secure-common.c
@@ -226,7 +226,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 		 * wrong given the subject matter.
 		 */
 		libpq_append_conn_error(conn, "certificate contains IP address with invalid length %zu",
-						  iplen);
+								iplen);
 		return -1;
 	}
 
@@ -235,7 +235,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 	if (!addrstr)
 	{
 		libpq_append_conn_error(conn, "could not convert certificate's IP address to string: %s",
-						  strerror_r(errno, sebuf, sizeof(sebuf)));
+								strerror_r(errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -292,7 +292,7 @@ pq_verify_peer_name_matches_certificate(PGconn *conn)
 		else if (names_examined == 1)
 		{
 			libpq_append_conn_error(conn, "server certificate for \"%s\" does not match host name \"%s\"",
-							  first_name, host);
+									first_name, host);
 		}
 		else
 		{
diff --git a/src/interfaces/libpq/fe-secure-gssapi.c b/src/interfaces/libpq/fe-secure-gssapi.c
index 038e847b7e9..0af4de941af 100644
--- a/src/interfaces/libpq/fe-secure-gssapi.c
+++ b/src/interfaces/libpq/fe-secure-gssapi.c
@@ -213,8 +213,8 @@ pg_GSS_write(PGconn *conn, const void *ptr, size_t len)
 		if (output.length > PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "client tried to send oversize GSSAPI packet (%zu > %zu)",
-							  (size_t) output.length,
-							  PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
+									(size_t) output.length,
+									PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			goto cleanup;
 		}
@@ -349,8 +349,8 @@ pg_GSS_read(PGconn *conn, void *ptr, size_t len)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			return -1;
 		}
@@ -590,8 +590,8 @@ pqsecure_open_gss(PGconn *conn)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			return PGRES_POLLING_FAILED;
 		}
 
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index 6a4431ddfe9..e6da377fb9d 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -213,12 +213,12 @@ rloop:
 				if (result_errno == EPIPE ||
 					result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -313,12 +313,12 @@ pgtls_write(PGconn *conn, const void *ptr, size_t len)
 				result_errno = SOCK_ERRNO;
 				if (result_errno == EPIPE || result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -415,7 +415,7 @@ pgtls_get_peer_certificate_hash(PGconn *conn, size_t *len)
 			if (algo_type == NULL)
 			{
 				libpq_append_conn_error(conn, "could not find digest for NID %s",
-								  OBJ_nid2sn(algo_nid));
+										OBJ_nid2sn(algo_nid));
 				return NULL;
 			}
 			break;
@@ -967,7 +967,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_min_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for minimum SSL protocol version",
-							  conn->ssl_min_protocol_version);
+									conn->ssl_min_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -993,7 +993,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_max_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for maximum SSL protocol version",
-							  conn->ssl_max_protocol_version);
+									conn->ssl_max_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1037,7 +1037,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read root certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1089,10 +1089,10 @@ initialize_SSL(PGconn *conn)
 			 */
 			if (fnbuf[0] == '\0')
 				libpq_append_conn_error(conn, "could not get home directory to locate root certificate file\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.");
+										"Either provide the file or change sslmode to disable server certificate verification.");
 			else
 				libpq_append_conn_error(conn, "root certificate file \"%s\" does not exist\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
+										"Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1122,7 +1122,7 @@ initialize_SSL(PGconn *conn)
 		if (errno != ENOENT && errno != ENOTDIR)
 		{
 			libpq_append_conn_error(conn, "could not open certificate file \"%s\": %s",
-							  fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
+									fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1140,7 +1140,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1239,7 +1239,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				free(engine_str);
 				return -1;
@@ -1250,7 +1250,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not initialize SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				ENGINE_free(conn->engine);
 				conn->engine = NULL;
@@ -1265,7 +1265,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not read private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1278,7 +1278,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1315,10 +1315,10 @@ initialize_SSL(PGconn *conn)
 		{
 			if (errno == ENOENT)
 				libpq_append_conn_error(conn, "certificate present, but not private key file \"%s\"",
-								  fnbuf);
+										fnbuf);
 			else
 				libpq_append_conn_error(conn, "could not stat private key file \"%s\": %m",
-								  fnbuf);
+										fnbuf);
 			return -1;
 		}
 
@@ -1326,7 +1326,7 @@ initialize_SSL(PGconn *conn)
 		if (!S_ISREG(buf.st_mode))
 		{
 			libpq_append_conn_error(conn, "private key file \"%s\" is not a regular file",
-							  fnbuf);
+									fnbuf);
 			return -1;
 		}
 
@@ -1383,7 +1383,7 @@ initialize_SSL(PGconn *conn)
 			if (SSL_use_PrivateKey_file(conn->ssl, fnbuf, SSL_FILETYPE_ASN1) != 1)
 			{
 				libpq_append_conn_error(conn, "could not load private key file \"%s\": %s",
-								  fnbuf, err);
+										fnbuf, err);
 				SSLerrfree(err);
 				return -1;
 			}
@@ -1399,7 +1399,7 @@ initialize_SSL(PGconn *conn)
 		char	   *err = SSLerrmessage(ERR_get_error());
 
 		libpq_append_conn_error(conn, "certificate does not match private key file \"%s\": %s",
-						  fnbuf, err);
+								fnbuf, err);
 		SSLerrfree(err);
 		return -1;
 	}
@@ -1452,7 +1452,7 @@ open_client_SSL(PGconn *conn)
 
 					if (r == -1)
 						libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-										  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					else
 						libpq_append_conn_error(conn, "SSL SYSCALL error: EOF detected");
 					pgtls_close(conn);
@@ -1494,12 +1494,12 @@ open_client_SSL(PGconn *conn)
 						case SSL_R_VERSION_TOO_LOW:
 #endif
 							libpq_append_conn_error(conn, "This may indicate that the server does not support any SSL protocol version between %s and %s.",
-											  conn->ssl_min_protocol_version ?
-											  conn->ssl_min_protocol_version :
-											  MIN_OPENSSL_TLS_VERSION,
-											  conn->ssl_max_protocol_version ?
-											  conn->ssl_max_protocol_version :
-											  MAX_OPENSSL_TLS_VERSION);
+													conn->ssl_min_protocol_version ?
+													conn->ssl_min_protocol_version :
+													MIN_OPENSSL_TLS_VERSION,
+													conn->ssl_max_protocol_version ?
+													conn->ssl_max_protocol_version :
+													MAX_OPENSSL_TLS_VERSION);
 							break;
 						default:
 							break;
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index 66e401bf3d9..8069e381424 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -255,14 +255,14 @@ pqsecure_raw_read(PGconn *conn, void *ptr, size_t len)
 			case EPIPE:
 			case ECONNRESET:
 				libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-								   "\tThis probably means the server terminated abnormally\n"
-								   "\tbefore or while processing the request.");
+										"\tThis probably means the server terminated abnormally\n"
+										"\tbefore or while processing the request.");
 				break;
 
 			default:
 				libpq_append_conn_error(conn, "could not receive data from server: %s",
-								  SOCK_STRERROR(result_errno,
-												sebuf, sizeof(sebuf)));
+										SOCK_STRERROR(result_errno,
+													  sebuf, sizeof(sebuf)));
 				break;
 		}
 	}
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 1dc264fe544..8890525cdf4 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -897,8 +897,8 @@ extern char *libpq_ngettext(const char *msgid, const char *msgid_plural, unsigne
  */
 #undef _
 
-extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...) pg_attribute_printf(2, 3);
-extern void libpq_append_conn_error(PGconn *conn, const char *fmt, ...) pg_attribute_printf(2, 3);
+extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...) pg_attribute_printf(2, 3);
+extern void libpq_append_conn_error(PGconn *conn, const char *fmt,...) pg_attribute_printf(2, 3);
 
 /*
  * These macros are needed to let error-handling code be portable between
-- 
2.34.1

From 4a6128fbf4ab7a190835a1c693dbd3bdb9e32ae4 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Fri, 17 Mar 2023 09:14:02 +0100
Subject: [PATCH v13 4/5] Add DNS based libpq load balancing test

This adds a test for DNS based load balancing in libpq. This patch was a
point of discussion due the fact that it requires changing /etc/hosts
for this test to run. Thus it was removed from the main libpq load
balancing patch, and added to its own patch for further discussion.

This patch also adds tests for DNS based retries of connections of libpq,
even when load balancing is disabled. We did not have tests for that
behaviour either.
---
 .cirrus.yml                                   |  16 ++-
 doc/src/sgml/regress.sgml                     |  11 +-
 .../libpq/t/004_load_balance_dns.pl           | 122 ++++++++++++++++++
 3 files changed, 147 insertions(+), 2 deletions(-)
 create mode 100644 src/interfaces/libpq/t/004_load_balance_dns.pl

diff --git a/.cirrus.yml b/.cirrus.yml
index 505c50f3285..04786174ed4 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -25,7 +25,7 @@ env:
   MTEST_ARGS: --print-errorlogs --no-rebuild -C build
   PGCTLTIMEOUT: 120 # avoids spurious failures during parallel tests
   TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
-  PG_TEST_EXTRA: kerberos ldap ssl
+  PG_TEST_EXTRA: kerberos ldap ssl load_balance
 
 
 # What files to preserve in case tests fail
@@ -313,6 +313,14 @@ task:
     mkdir -m 770 /tmp/cores
     chown root:postgres /tmp/cores
     sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core'
+
+  setup_hosts_file_script: |
+    cat >> /etc/hosts <<-EOF
+      127.0.0.1 pg-loadbalancetest
+      127.0.0.2 pg-loadbalancetest
+      127.0.0.3 pg-loadbalancetest
+    EOF
+
   setup_additional_packages_script: |
     #apt-get update
     #DEBIAN_FRONTEND=noninteractive apt-get -y install ...
@@ -564,6 +572,12 @@ task:
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
+  setup_hosts_file_script: |
+    echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    type c:\Windows\System32\Drivers\etc\hosts
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
diff --git a/doc/src/sgml/regress.sgml b/doc/src/sgml/regress.sgml
index 719e0a76985..dd7e4a200e9 100644
--- a/doc/src/sgml/regress.sgml
+++ b/doc/src/sgml/regress.sgml
@@ -256,7 +256,7 @@ make check-world -j8 >/dev/null
    <varname>PG_TEST_EXTRA</varname> to a whitespace-separated list, for
    example:
 <programlisting>
-make check-world PG_TEST_EXTRA='kerberos ldap ssl'
+make check-world PG_TEST_EXTRA='kerberos ldap ssl load_balance'
 </programlisting>
    The following values are currently supported:
    <variablelist>
@@ -290,6 +290,15 @@ make check-world PG_TEST_EXTRA='kerberos ldap ssl'
      </listitem>
     </varlistentry>
 
+    <varlistentry>
+     <term><literal>load_balance</literal></term>
+     <listitem>
+      <para>
+       Runs the test <filename>src/interfaces/libpq/t/004_load_balance_dns.pl</filename>.  This opens TCP/IP listen sockets.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry>
      <term><literal>wal_consistency_checking</literal></term>
      <listitem>
diff --git a/src/interfaces/libpq/t/004_load_balance_dns.pl b/src/interfaces/libpq/t/004_load_balance_dns.pl
new file mode 100644
index 00000000000..a4f40510954
--- /dev/null
+++ b/src/interfaces/libpq/t/004_load_balance_dns.pl
@@ -0,0 +1,122 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests loadbalancing based on a DNS entry that contains multiple records
+# for different IPs. Since setting up a DNS server is more effort than we
+# consider reasonable to run this test, this situation is instead immitated by
+# using a hosts file where a single hostname maps to multiple different IP
+# addresses. This test requires the adminstrator to add the following lines to
+# the hosts file (if we detect that this hasn't happend we skip the test):
+#
+# 127.0.0.1 pg-loadbalancetest
+# 127.0.0.2 pg-loadbalancetest
+# 127.0.0.3 pg-loadbalancetest
+#
+# Windows or Linux are required to run this test because these OSes allow
+# binding to 127.0.0.2 and 127.0.0.3 addresess by default, but other OSes
+# don't. We need to bind to different IP addresses, so that we can use these
+# different IP addresses in the hosts file.
+#
+# The hosts file needs to be prepared before running this test. We don't do it
+# on the fly, because it requires root permissions to change the hosts file. In
+# CI we set up the previously mentioned rules in the hosts file, so that this
+# load balancing method is tested.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os;
+
+# Checks for the requirements for testing load balancing method 2
+if (!$can_bind_to_127_0_0_2) {
+	plan skip_all => "OS could not bind to 127.0.0.2"
+}
+
+my $hosts_path;
+if ($windows_os) {
+	$hosts_path = 'c:\Windows\System32\Drivers\etc\hosts';
+}
+else
+{
+	$hosts_path = '/etc/hosts';
+}
+
+my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path);
+
+if ($hosts_content !~ m/pg-loadbalancetest/) {
+	# Host file is not prepared for this test
+	plan skip_all => "hosts file was not prepared for DNS load balance test"
+}
+
+if ($ENV{PG_TEST_EXTRA} !~ /\bload_balance\b/)
+{
+	plan skip_all => 'Potentially unsafe test load_balance not enabled in PG_TEST_EXTRA';
+}
+
+$PostgreSQL::Test::Cluster::use_tcp = 1;
+$PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1';
+my $port = PostgreSQL::Test::Cluster::get_free_port();
+my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port);
+my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# load_balance_hosts=disable should always choose the first one.
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=disable",
+	"load_balance_hosts=disable connects to the first node",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+
+# Statistically the following loop with load_balance_hosts=random will almost
+# certainly connect at least once to each of the nodes. The chance of that not
+# happening is so small that it's negligible: (2/3)^50 = 1.56832855e-9
+foreach my $i (1 .. 50) {
+	$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random",
+		"seed 1234 selects node 1 first",
+		sql => "SELECT 'connect1'");
+}
+
+my $node1_occurences = () = $node1->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node2_occurences = () = $node2->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node3_occurences = () = $node3->log_content() =~ /statement: SELECT 'connect1'/g;
+
+my $total_occurences = $node1_occurences + $node2_occurences + $node3_occurences;
+
+ok($node1_occurences > 1, "expected at least one execution on node1, found $node1_occurences");
+ok($node2_occurences > 1, "expected at least one execution on node2, found $node2_occurences");
+ok($node3_occurences > 1, "expected at least one execution on node3, found $node3_occurences");
+ok($total_occurences == 50, "expected 50 executions across all nodes, found $total_occurences");
+
+$node1->stop();
+$node2->stop();
+
+# load_balance_hosts=disable should continue trying hosts until it finds a
+# working one.
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=disable",
+	"load_balance_hosts=disable continues until it connects to the a working node",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+# Also with load_balance_hosts=random we continue to the next nodes if previous
+# ones are down. Connect a few times to make sure it's not just lucky.
+foreach my $i (1 .. 5) {
+	$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random",
+		"load_balance_hosts=random continues until it connects to the a working node",
+		sql => "SELECT 'connect4'",
+		log_like => [qr/statement: SELECT 'connect4'/]);
+}
+
+done_testing();
-- 
2.34.1

From 80ed091a7486669b81f9bfed9cbcb520973a9189 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 30 Nov 2022 10:07:19 +0100
Subject: [PATCH v14 1/5] libpq: Run pgindent after a9e9a9f32b3

It seems that pgindent was not run after the error handling refactor in
commit a9e9a9f32b35edf129c88e8b929ef223f8511f59. This fixes that and
also addresses a few other things pgindent wanted to change in libpq.
---
 src/interfaces/libpq/fe-exec.c           | 16 +++---
 src/interfaces/libpq/fe-lobj.c           | 42 ++++++++--------
 src/interfaces/libpq/fe-misc.c           | 10 ++--
 src/interfaces/libpq/fe-protocol3.c      |  2 +-
 src/interfaces/libpq/fe-secure-common.c  |  6 +--
 src/interfaces/libpq/fe-secure-gssapi.c  | 12 ++---
 src/interfaces/libpq/fe-secure-openssl.c | 64 ++++++++++++------------
 src/interfaces/libpq/fe-secure.c         |  8 +--
 src/interfaces/libpq/libpq-int.h         |  4 +-
 9 files changed, 82 insertions(+), 82 deletions(-)

diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index ec62550e385..0c2dae6ed9e 100644
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -1444,7 +1444,7 @@ PQsendQueryInternal(PGconn *conn, const char *query, bool newQuery)
 	if (conn->pipelineStatus != PQ_PIPELINE_OFF)
 	{
 		libpq_append_conn_error(conn, "%s not allowed in pipeline mode",
-						  "PQsendQuery");
+								"PQsendQuery");
 		return 0;
 	}
 
@@ -1512,7 +1512,7 @@ PQsendQueryParams(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1558,7 +1558,7 @@ PQsendPrepare(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -1652,7 +1652,7 @@ PQsendQueryPrepared(PGconn *conn,
 	if (nParams < 0 || nParams > PQ_QUERY_PARAM_MAX_LIMIT)
 	{
 		libpq_append_conn_error(conn, "number of parameters must be between 0 and %d",
-						   PQ_QUERY_PARAM_MAX_LIMIT);
+								PQ_QUERY_PARAM_MAX_LIMIT);
 		return 0;
 	}
 
@@ -2099,10 +2099,9 @@ PQgetResult(PGconn *conn)
 
 			/*
 			 * We're about to return the NULL that terminates the round of
-			 * results from the current query; prepare to send the results
-			 * of the next query, if any, when we're called next.  If there's
-			 * no next element in the command queue, this gets us in IDLE
-			 * state.
+			 * results from the current query; prepare to send the results of
+			 * the next query, if any, when we're called next.  If there's no
+			 * next element in the command queue, this gets us in IDLE state.
 			 */
 			pqPipelineProcessQueue(conn);
 			res = NULL;			/* query is complete */
@@ -3047,6 +3046,7 @@ pqPipelineProcessQueue(PGconn *conn)
 			return;
 
 		case PGASYNC_IDLE:
+
 			/*
 			 * If we're in IDLE mode and there's some command in the queue,
 			 * get us into PIPELINE_IDLE mode and process normally.  Otherwise
diff --git a/src/interfaces/libpq/fe-lobj.c b/src/interfaces/libpq/fe-lobj.c
index 4cb6a468597..206266fd043 100644
--- a/src/interfaces/libpq/fe-lobj.c
+++ b/src/interfaces/libpq/fe-lobj.c
@@ -142,7 +142,7 @@ lo_truncate(PGconn *conn, int fd, size_t len)
 	if (conn->lobjfuncs->fn_lo_truncate == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate");
+								"lo_truncate");
 		return -1;
 	}
 
@@ -205,7 +205,7 @@ lo_truncate64(PGconn *conn, int fd, pg_int64 len)
 	if (conn->lobjfuncs->fn_lo_truncate64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_truncate64");
+								"lo_truncate64");
 		return -1;
 	}
 
@@ -395,7 +395,7 @@ lo_lseek64(PGconn *conn, int fd, pg_int64 offset, int whence)
 	if (conn->lobjfuncs->fn_lo_lseek64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek64");
+								"lo_lseek64");
 		return -1;
 	}
 
@@ -485,7 +485,7 @@ lo_create(PGconn *conn, Oid lobjId)
 	if (conn->lobjfuncs->fn_lo_create == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_create");
+								"lo_create");
 		return InvalidOid;
 	}
 
@@ -558,7 +558,7 @@ lo_tell64(PGconn *conn, int fd)
 	if (conn->lobjfuncs->fn_lo_tell64 == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell64");
+								"lo_tell64");
 		return -1;
 	}
 
@@ -667,7 +667,7 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 	if (fd < 0)
 	{							/* error */
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -723,8 +723,8 @@ lo_import_internal(PGconn *conn, const char *filename, Oid oid)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not read from file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return InvalidOid;
 	}
 
@@ -778,8 +778,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 		/* deliberately overwrite any error from lo_close */
 		pqClearConnErrorState(conn);
 		libpq_append_conn_error(conn, "could not open file \"%s\": %s",
-						  filename,
-						  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+								filename,
+								strerror_r(save_errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -799,8 +799,8 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 			/* deliberately overwrite any error from lo_close */
 			pqClearConnErrorState(conn);
 			libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-							  filename,
-							  strerror_r(save_errno, sebuf, sizeof(sebuf)));
+									filename,
+									strerror_r(save_errno, sebuf, sizeof(sebuf)));
 			return -1;
 		}
 	}
@@ -822,7 +822,7 @@ lo_export(PGconn *conn, Oid lobjId, const char *filename)
 	if (close(fd) != 0 && result >= 0)
 	{
 		libpq_append_conn_error(conn, "could not write to file \"%s\": %s",
-						  filename, strerror_r(errno, sebuf, sizeof(sebuf)));
+								filename, strerror_r(errno, sebuf, sizeof(sebuf)));
 		result = -1;
 	}
 
@@ -954,56 +954,56 @@ lo_initialize(PGconn *conn)
 	if (lobjfuncs->fn_lo_open == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_open");
+								"lo_open");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_close == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_close");
+								"lo_close");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_creat == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_creat");
+								"lo_creat");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_unlink == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_unlink");
+								"lo_unlink");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_lseek == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_lseek");
+								"lo_lseek");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_tell == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lo_tell");
+								"lo_tell");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_read == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "loread");
+								"loread");
 		free(lobjfuncs);
 		return -1;
 	}
 	if (lobjfuncs->fn_lo_write == 0)
 	{
 		libpq_append_conn_error(conn, "cannot determine OID of function %s",
-						  "lowrite");
+								"lowrite");
 		free(lobjfuncs);
 		return -1;
 	}
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 3653a1a8a62..660cdec93c9 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -749,8 +749,8 @@ retry4:
 	 */
 definitelyEOF:
 	libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-					   "\tThis probably means the server terminated abnormally\n"
-					   "\tbefore or while processing the request.");
+							"\tThis probably means the server terminated abnormally\n"
+							"\tbefore or while processing the request.");
 
 	/* Come here if lower-level code already set a suitable errorMessage */
 definitelyFailed:
@@ -1067,7 +1067,7 @@ pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time)
 		char		sebuf[PG_STRERROR_R_BUFLEN];
 
 		libpq_append_conn_error(conn, "%s() failed: %s", "select",
-						  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+								SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 	}
 
 	return result;
@@ -1280,7 +1280,7 @@ libpq_ngettext(const char *msgid, const char *msgid_plural, unsigned long n)
  * newline.
  */
 void
-libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
+libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
@@ -1309,7 +1309,7 @@ libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...)
  * format should not end with a newline.
  */
 void
-libpq_append_conn_error(PGconn *conn, const char *fmt, ...)
+libpq_append_conn_error(PGconn *conn, const char *fmt,...)
 {
 	int			save_errno = errno;
 	bool		done;
diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index 8ab6a884165..b79d74f7489 100644
--- a/src/interfaces/libpq/fe-protocol3.c
+++ b/src/interfaces/libpq/fe-protocol3.c
@@ -466,7 +466,7 @@ static void
 handleSyncLoss(PGconn *conn, char id, int msgLength)
 {
 	libpq_append_conn_error(conn, "lost synchronization with server: got message type \"%c\", length %d",
-					  id, msgLength);
+							id, msgLength);
 	/* build an error result holding the error message */
 	pqSaveErrorResult(conn);
 	conn->asyncStatus = PGASYNC_READY;	/* drop out of PQgetResult wait loop */
diff --git a/src/interfaces/libpq/fe-secure-common.c b/src/interfaces/libpq/fe-secure-common.c
index de115b37649..3ecc7bf6159 100644
--- a/src/interfaces/libpq/fe-secure-common.c
+++ b/src/interfaces/libpq/fe-secure-common.c
@@ -226,7 +226,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 		 * wrong given the subject matter.
 		 */
 		libpq_append_conn_error(conn, "certificate contains IP address with invalid length %zu",
-						  iplen);
+								iplen);
 		return -1;
 	}
 
@@ -235,7 +235,7 @@ pq_verify_peer_name_matches_certificate_ip(PGconn *conn,
 	if (!addrstr)
 	{
 		libpq_append_conn_error(conn, "could not convert certificate's IP address to string: %s",
-						  strerror_r(errno, sebuf, sizeof(sebuf)));
+								strerror_r(errno, sebuf, sizeof(sebuf)));
 		return -1;
 	}
 
@@ -292,7 +292,7 @@ pq_verify_peer_name_matches_certificate(PGconn *conn)
 		else if (names_examined == 1)
 		{
 			libpq_append_conn_error(conn, "server certificate for \"%s\" does not match host name \"%s\"",
-							  first_name, host);
+									first_name, host);
 		}
 		else
 		{
diff --git a/src/interfaces/libpq/fe-secure-gssapi.c b/src/interfaces/libpq/fe-secure-gssapi.c
index 038e847b7e9..0af4de941af 100644
--- a/src/interfaces/libpq/fe-secure-gssapi.c
+++ b/src/interfaces/libpq/fe-secure-gssapi.c
@@ -213,8 +213,8 @@ pg_GSS_write(PGconn *conn, const void *ptr, size_t len)
 		if (output.length > PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "client tried to send oversize GSSAPI packet (%zu > %zu)",
-							  (size_t) output.length,
-							  PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
+									(size_t) output.length,
+									PQ_GSS_SEND_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			goto cleanup;
 		}
@@ -349,8 +349,8 @@ pg_GSS_read(PGconn *conn, void *ptr, size_t len)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			errno = EIO;		/* for lack of a better idea */
 			return -1;
 		}
@@ -590,8 +590,8 @@ pqsecure_open_gss(PGconn *conn)
 		if (input.length > PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32))
 		{
 			libpq_append_conn_error(conn, "oversize GSSAPI packet sent by the server (%zu > %zu)",
-							  (size_t) input.length,
-							  PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
+									(size_t) input.length,
+									PQ_GSS_RECV_BUFFER_SIZE - sizeof(uint32));
 			return PGRES_POLLING_FAILED;
 		}
 
diff --git a/src/interfaces/libpq/fe-secure-openssl.c b/src/interfaces/libpq/fe-secure-openssl.c
index 6a4431ddfe9..e6da377fb9d 100644
--- a/src/interfaces/libpq/fe-secure-openssl.c
+++ b/src/interfaces/libpq/fe-secure-openssl.c
@@ -213,12 +213,12 @@ rloop:
 				if (result_errno == EPIPE ||
 					result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -313,12 +313,12 @@ pgtls_write(PGconn *conn, const void *ptr, size_t len)
 				result_errno = SOCK_ERRNO;
 				if (result_errno == EPIPE || result_errno == ECONNRESET)
 					libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-									   "\tThis probably means the server terminated abnormally\n"
-									   "\tbefore or while processing the request.");
+											"\tThis probably means the server terminated abnormally\n"
+											"\tbefore or while processing the request.");
 				else
 					libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-									  SOCK_STRERROR(result_errno,
-													sebuf, sizeof(sebuf)));
+											SOCK_STRERROR(result_errno,
+														  sebuf, sizeof(sebuf)));
 			}
 			else
 			{
@@ -415,7 +415,7 @@ pgtls_get_peer_certificate_hash(PGconn *conn, size_t *len)
 			if (algo_type == NULL)
 			{
 				libpq_append_conn_error(conn, "could not find digest for NID %s",
-								  OBJ_nid2sn(algo_nid));
+										OBJ_nid2sn(algo_nid));
 				return NULL;
 			}
 			break;
@@ -967,7 +967,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_min_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for minimum SSL protocol version",
-							  conn->ssl_min_protocol_version);
+									conn->ssl_min_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -993,7 +993,7 @@ initialize_SSL(PGconn *conn)
 		if (ssl_max_ver == -1)
 		{
 			libpq_append_conn_error(conn, "invalid value \"%s\" for maximum SSL protocol version",
-							  conn->ssl_max_protocol_version);
+									conn->ssl_max_protocol_version);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1037,7 +1037,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read root certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1089,10 +1089,10 @@ initialize_SSL(PGconn *conn)
 			 */
 			if (fnbuf[0] == '\0')
 				libpq_append_conn_error(conn, "could not get home directory to locate root certificate file\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.");
+										"Either provide the file or change sslmode to disable server certificate verification.");
 			else
 				libpq_append_conn_error(conn, "root certificate file \"%s\" does not exist\n"
-								   "Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
+										"Either provide the file or change sslmode to disable server certificate verification.", fnbuf);
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1122,7 +1122,7 @@ initialize_SSL(PGconn *conn)
 		if (errno != ENOENT && errno != ENOTDIR)
 		{
 			libpq_append_conn_error(conn, "could not open certificate file \"%s\": %s",
-							  fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
+									fnbuf, strerror_r(errno, sebuf, sizeof(sebuf)));
 			SSL_CTX_free(SSL_context);
 			return -1;
 		}
@@ -1140,7 +1140,7 @@ initialize_SSL(PGconn *conn)
 			char	   *err = SSLerrmessage(ERR_get_error());
 
 			libpq_append_conn_error(conn, "could not read certificate file \"%s\": %s",
-							  fnbuf, err);
+									fnbuf, err);
 			SSLerrfree(err);
 			SSL_CTX_free(SSL_context);
 			return -1;
@@ -1239,7 +1239,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				free(engine_str);
 				return -1;
@@ -1250,7 +1250,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not initialize SSL engine \"%s\": %s",
-								  engine_str, err);
+										engine_str, err);
 				SSLerrfree(err);
 				ENGINE_free(conn->engine);
 				conn->engine = NULL;
@@ -1265,7 +1265,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not read private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1278,7 +1278,7 @@ initialize_SSL(PGconn *conn)
 				char	   *err = SSLerrmessage(ERR_get_error());
 
 				libpq_append_conn_error(conn, "could not load private SSL key \"%s\" from engine \"%s\": %s",
-								  engine_colon, engine_str, err);
+										engine_colon, engine_str, err);
 				SSLerrfree(err);
 				ENGINE_finish(conn->engine);
 				ENGINE_free(conn->engine);
@@ -1315,10 +1315,10 @@ initialize_SSL(PGconn *conn)
 		{
 			if (errno == ENOENT)
 				libpq_append_conn_error(conn, "certificate present, but not private key file \"%s\"",
-								  fnbuf);
+										fnbuf);
 			else
 				libpq_append_conn_error(conn, "could not stat private key file \"%s\": %m",
-								  fnbuf);
+										fnbuf);
 			return -1;
 		}
 
@@ -1326,7 +1326,7 @@ initialize_SSL(PGconn *conn)
 		if (!S_ISREG(buf.st_mode))
 		{
 			libpq_append_conn_error(conn, "private key file \"%s\" is not a regular file",
-							  fnbuf);
+									fnbuf);
 			return -1;
 		}
 
@@ -1383,7 +1383,7 @@ initialize_SSL(PGconn *conn)
 			if (SSL_use_PrivateKey_file(conn->ssl, fnbuf, SSL_FILETYPE_ASN1) != 1)
 			{
 				libpq_append_conn_error(conn, "could not load private key file \"%s\": %s",
-								  fnbuf, err);
+										fnbuf, err);
 				SSLerrfree(err);
 				return -1;
 			}
@@ -1399,7 +1399,7 @@ initialize_SSL(PGconn *conn)
 		char	   *err = SSLerrmessage(ERR_get_error());
 
 		libpq_append_conn_error(conn, "certificate does not match private key file \"%s\": %s",
-						  fnbuf, err);
+								fnbuf, err);
 		SSLerrfree(err);
 		return -1;
 	}
@@ -1452,7 +1452,7 @@ open_client_SSL(PGconn *conn)
 
 					if (r == -1)
 						libpq_append_conn_error(conn, "SSL SYSCALL error: %s",
-										  SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
+												SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
 					else
 						libpq_append_conn_error(conn, "SSL SYSCALL error: EOF detected");
 					pgtls_close(conn);
@@ -1494,12 +1494,12 @@ open_client_SSL(PGconn *conn)
 						case SSL_R_VERSION_TOO_LOW:
 #endif
 							libpq_append_conn_error(conn, "This may indicate that the server does not support any SSL protocol version between %s and %s.",
-											  conn->ssl_min_protocol_version ?
-											  conn->ssl_min_protocol_version :
-											  MIN_OPENSSL_TLS_VERSION,
-											  conn->ssl_max_protocol_version ?
-											  conn->ssl_max_protocol_version :
-											  MAX_OPENSSL_TLS_VERSION);
+													conn->ssl_min_protocol_version ?
+													conn->ssl_min_protocol_version :
+													MIN_OPENSSL_TLS_VERSION,
+													conn->ssl_max_protocol_version ?
+													conn->ssl_max_protocol_version :
+													MAX_OPENSSL_TLS_VERSION);
 							break;
 						default:
 							break;
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index 66e401bf3d9..8069e381424 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -255,14 +255,14 @@ pqsecure_raw_read(PGconn *conn, void *ptr, size_t len)
 			case EPIPE:
 			case ECONNRESET:
 				libpq_append_conn_error(conn, "server closed the connection unexpectedly\n"
-								   "\tThis probably means the server terminated abnormally\n"
-								   "\tbefore or while processing the request.");
+										"\tThis probably means the server terminated abnormally\n"
+										"\tbefore or while processing the request.");
 				break;
 
 			default:
 				libpq_append_conn_error(conn, "could not receive data from server: %s",
-								  SOCK_STRERROR(result_errno,
-												sebuf, sizeof(sebuf)));
+										SOCK_STRERROR(result_errno,
+													  sebuf, sizeof(sebuf)));
 				break;
 		}
 	}
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 1dc264fe544..8890525cdf4 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -897,8 +897,8 @@ extern char *libpq_ngettext(const char *msgid, const char *msgid_plural, unsigne
  */
 #undef _
 
-extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt, ...) pg_attribute_printf(2, 3);
-extern void libpq_append_conn_error(PGconn *conn, const char *fmt, ...) pg_attribute_printf(2, 3);
+extern void libpq_append_error(PQExpBuffer errorMessage, const char *fmt,...) pg_attribute_printf(2, 3);
+extern void libpq_append_conn_error(PGconn *conn, const char *fmt,...) pg_attribute_printf(2, 3);
 
 /*
  * These macros are needed to let error-handling code be portable between

base-commit: d69c404c4cc5985d8ae5b5ed38bed3400b317f82
-- 
2.34.1

From 1bae1c504d832a3f953b4ab4a74ae820abb1793e Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Wed, 25 Jan 2023 10:22:41 +0100
Subject: [PATCH v14 2/5] Refactor libpq to store addrinfo in a libpq owned
 array

This refactors libpq to copy addrinfos returned by getaddrinfo to
memory owned by us. This refactoring is useful for two upcoming patches,
which need to change the addrinfo list in some way. Doing that with the
original addrinfo list is risky since we don't control how memory is
freed. Also changing the contents of a C array is quite a bit easier
than changing a linked list.

As a nice side effect of this refactor the is that mechanism for
iteration over addresses in PQconnectPoll is now identical to its
iteration over hosts.
---
 src/include/libpq/pqcomm.h        |   6 ++
 src/interfaces/libpq/fe-connect.c | 107 +++++++++++++++++++++---------
 src/interfaces/libpq/libpq-int.h  |   7 +-
 src/tools/pgindent/typedefs.list  |   1 +
 4 files changed, 87 insertions(+), 34 deletions(-)

diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index bff7dd18a23..c85090259d9 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+} AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index b9f899c552e..4a0ea51a864 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -383,6 +383,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *connstr,
@@ -2242,7 +2243,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2286,11 +2287,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2437,9 +2438,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2452,6 +2453,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2492,7 +2494,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2515,8 +2517,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
 											ch->host, gai_strerror(ret));
@@ -2527,8 +2529,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
 											ch->hostaddr, gai_strerror(ret));
@@ -2537,7 +2539,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2552,8 +2554,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
 											portstr, gai_strerror(ret));
@@ -2562,8 +2564,14 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		if (!store_conn_addrinfo(conn, addrlist))
+		{
+			pg_freeaddrinfo_all(hint.ai_family, addrlist);
+			libpq_append_conn_error(conn, "out of memory");
+			goto error_return;
+		}
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2620,31 +2628,30 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
 					int			sock_type;
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2679,7 +2686,7 @@ keep_going:						/* We will come back to here until there is
 					 */
 					sock_type |= SOCK_NONBLOCK;
 #endif
-					conn->sock = socket(addr_cur->ai_family, sock_type, 0);
+					conn->sock = socket(addr_cur->family, sock_type, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2690,7 +2697,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2716,7 +2723,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2747,7 +2754,7 @@ keep_going:						/* We will come back to here until there is
 #endif							/* F_SETFD */
 #endif
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2839,8 +2846,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4263,6 +4270,45 @@ freePGconn(PGconn *conn)
 	free(conn);
 }
 
+/*
+ * Copies over the addrinfos from addrlist to the PGconn. The reason we do this
+ * so that we can edit the resulting list as we please, because now the memory
+ * is owned by us. Changing the original addrinfo directly is risky, since we
+ * don't control how the memory is freed and by changing it we might confuse
+ * the implementation of freeaddrinfo.
+ */
+static bool
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+		return false;
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	return true;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4270,11 +4316,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 8890525cdf4..8f96c52e6c3 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -470,9 +470,10 @@ struct pg_conn
 	PGTargetServerType target_server_type;	/* desired session properties */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
-	int			addrlist_family;	/* needed to know how to free addrlist */
+	int			naddr;			/* number of addresses returned by getaddrinfo */
+	int			whichaddr;		/* the address currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	bool		send_appname;	/* okay to send application_name? */
 
 	/* Miscellaneous stuff */
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 097f42e1b34..5c5aa8bf4c9 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -26,6 +26,7 @@ AcquireSampleRowsFunc
 ActionList
 ActiveSnapshotElt
 AddForeignUpdateTargets_function
+AddrInfo
 AffixNode
 AffixNodeData
 AfterTriggerEvent
-- 
2.34.1

From 52272bd42588387ffed1aba63d017b3797ce6b71 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <github-tech@jeltef.nl>
Date: Mon, 12 Sep 2022 09:44:06 +0200
Subject: [PATCH v14 3/5] Support load balancing in libpq

This adds support for load balancing to libpq using the newly added
load_balance_hosts parameter. When setting the load_balance_hosts
parameter to random, hosts and addresses will be connected to in a
random order. This then results in load balancing across these
hosts/addresses if multiple clients do this at the same time.

This patch implements two levels of random load balancing:
1. The given hosts are randomly shuffled, before resolving them
    one-by-one.
2. Once a host its addresses get resolved, those addresses are shuffled,
    before trying to connect to them one-by-one.
---
 doc/src/sgml/libpq.sgml                       |  74 ++++++++++++
 src/interfaces/libpq/fe-connect.c             | 105 ++++++++++++++++++
 src/interfaces/libpq/libpq-int.h              |  17 ++-
 src/interfaces/libpq/meson.build              |   2 +
 .../libpq/t/003_load_balance_host_list.pl     |  82 ++++++++++++++
 src/test/perl/PostgreSQL/Test/Cluster.pm      |  16 +++
 src/tools/pgindent/typedefs.list              |   1 +
 7 files changed, 296 insertions(+), 1 deletion(-)
 create mode 100644 src/interfaces/libpq/t/003_load_balance_host_list.pl

diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 9ee5532c076..6ea2912eff3 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -2059,6 +2059,80 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="libpq-connect-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls the order in which the client tries to connect to the available
+        hosts and addresses. Once a connection attempt is successful no other
+        hosts and addresses will be tried. This parameter is typically used in
+        combination with multiple host names or a DNS record that returns
+        multiple IPs. This parameter can be used in combination with
+        <xref linkend="libpq-connect-target-session-attrs"/>
+        to, for example, load balance over standby servers only. Once successfully
+        connected, subsequent queries on the returned connection will all be
+        sent to the same server. There are currently two modes:
+        <variablelist>
+         <varlistentry>
+          <term><literal>disable</literal> (default)</term>
+          <listitem>
+           <para>
+            No load balancing across hosts is performed. The order in which
+            hosts and addresses are tried is the same for every connection
+            attempt: Hosts are tried in the order in which they are provided and
+            addresses are tried in the order they are received from DNS or a
+            hosts file.
+           </para>
+
+           <para>
+            While this may sound similar to round-robin load balancing, it is
+            not. Round-robin load balancing requires that subsequent connection
+            attempts start iterating over hosts where the previous connection
+            attempt stopped. This is not done when using <literal>disable</literal>.
+            Instead every connection attempt starts at <emphasis>the same</emphasis>
+            first host. So, if that host is online and accepting connections, all
+            clients will connect to it and all of the other hosts in the
+            list get no connections at all.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>random</literal></term>
+          <listitem>
+           <para>
+            Hosts and addresses are tried in random order. This value is mostly
+            useful when opening multiple connections at the same time, possibly
+            from different machines. This way connections can be load balanced
+            across multiple <productname>PostgreSQL</productname> servers.
+           </para>
+           <para>
+            While random load balancing, due to its random nature, will almost
+            never result in a completely uniform distribution, it statistically
+            gets quite close. One important aspect here is that this algorithm
+            uses two levels of random choices: First the hosts
+            will be resolved in random order. Then secondly, before resolving
+            the next host, all resolved addresses for the current host will be
+            tried in random order. This behaviour can skew the amount of
+            connections each node gets greatly in certain cases, for instance
+            when some hosts resolve to more addresses than others. But such a
+            skew can also be used on purpose, e.g. to increase the number of
+            connections a larger server gets by providing its hostname multiple
+            times in the host string.
+           </para>
+           <para>
+            When using this value it's recommended to also configure a reasonable
+            value for <xref linkend="libpq-connect-connect-timeout"/>. Because then,
+            if one of the nodes that are used for load balancing is not responding,
+            a new node will be tried.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
    </para>
   </sect2>
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 4a0ea51a864..23fd5e8fa48 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -123,6 +123,7 @@ static int	ldapServiceLookup(const char *purl, PQconninfoOption *options,
 #define DefaultChannelBinding	"disable"
 #endif
 #define DefaultTargetSessionAttrs	"any"
+#define DefaultLoadBalanceHosts	"disable"
 #ifdef USE_SSL
 #define DefaultSSLMode "prefer"
 #else
@@ -345,6 +346,11 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Target-Session-Attrs", "", 15, /* sizeof("prefer-standby") = 15 */
 	offsetof(struct pg_conn, target_session_attrs)},
 
+	{"load_balance_hosts", "PGLOADBALANCEHOSTS",
+		DefaultLoadBalanceHosts, NULL,
+		"Load-Balance-Hosts", "", 8,	/* sizeof("disable") = 8 */
+	offsetof(struct pg_conn, load_balance_hosts)},
+
 	/* Terminating entry --- MUST BE LAST */
 	{NULL, NULL, NULL, NULL,
 	NULL, NULL, 0}
@@ -429,6 +435,8 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static bool parse_int_param(const char *value, int *result, PGconn *conn,
+							const char *context);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1013,6 +1021,32 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on the connection address,
+ * timestamp and PID.
+ */
+static bool
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		struct timeval tval = {0};
+
+		gettimeofday(&tval, NULL);
+
+		rseed = ((uint64) conn) ^
+			((uint64) getpid()) ^
+			((uint64) tval.tv_usec) ^
+			((uint64) tval.tv_sec);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+	return true;
+}
+
 /*
  *		connectOptions2
  *
@@ -1566,6 +1600,50 @@ connectOptions2(PGconn *conn)
 	else
 		conn->target_server_type = SERVER_TYPE_ANY;
 
+	/*
+	 * validate load_balance_hosts option, and set load_balance_type
+	 */
+	if (conn->load_balance_hosts)
+	{
+		if (strcmp(conn->load_balance_hosts, "disable") == 0)
+			conn->load_balance_type = LOAD_BALANCE_DISABLE;
+		else if (strcmp(conn->load_balance_hosts, "random") == 0)
+			conn->load_balance_type = LOAD_BALANCE_RANDOM;
+		else
+		{
+			conn->status = CONNECTION_BAD;
+			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
+									"load_balance_hosts",
+									conn->load_balance_hosts);
+			return false;
+		}
+	}
+	else
+		conn->load_balance_type = LOAD_BALANCE_DISABLE;
+
+	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+	{
+		if (!libpq_prng_init(conn))
+			return false;
+
+		/*
+		 * This is the "inside-out" variant of the Fisher-Yates shuffle
+		 * algorithm. Notionally, we append each new value to the array and
+		 * then swap it with a randomly-chosen array element (possibly
+		 * including itself, else we fail to generate permutations with the
+		 * last integer last).  The swap step can be optimized by combining it
+		 * with the insertion.
+		 */
+		for (i = 1; i < conn->nconnhost; i++)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
 	/*
 	 * Resolve special "auto" client_encoding from the locale
 	 */
@@ -2572,6 +2650,32 @@ keep_going:						/* We will come back to here until there is
 		}
 		pg_freeaddrinfo_all(hint.ai_family, addrlist);
 
+		/*
+		 * If random load balancing is enabled we shuffle the addresses.
+		 */
+		if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+		{
+			/*
+			 * This is the "inside-out" variant of the Fisher-Yates shuffle
+			 * algorithm. Notionally, we append each new value to the array
+			 * and then swap it with a randomly-chosen array element (possibly
+			 * including itself, else we fail to generate permutations with
+			 * the last integer last).  The swap step can be optimized by
+			 * combining it with the insertion.
+			 *
+			 * We don't need to initialize conn->prng_state here, because that
+			 * already happened in connectOptions2.
+			 */
+			for (int i = 1; i < conn->naddr; i++)
+			{
+				int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+				AddrInfo	temp = conn->addr[j];
+
+				conn->addr[j] = conn->addr[i];
+				conn->addr[i] = temp;
+			}
+		}
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -4264,6 +4368,7 @@ freePGconn(PGconn *conn)
 	free(conn->outBuffer);
 	free(conn->rowBuf);
 	free(conn->target_session_attrs);
+	free(conn->load_balance_hosts);
 	termPQExpBuffer(&conn->errorMessage);
 	termPQExpBuffer(&conn->workBuffer);
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 8f96c52e6c3..ff79396c0be 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -26,7 +26,8 @@
 #include <netdb.h>
 #include <sys/socket.h>
 #include <time.h>
-#ifndef WIN32
+/* MinGW has sys/time.h, but MSVC doesn't */
+#ifndef _MSC_VER
 #include <sys/time.h>
 #endif
 
@@ -82,6 +83,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -242,6 +245,13 @@ typedef enum
 	SERVER_TYPE_PREFER_STANDBY_PASS2	/* second pass - behaves same as ANY */
 } PGTargetServerType;
 
+/* Target server type (decoded value of load_balance_hosts) */
+typedef enum
+{
+	LOAD_BALANCE_DISABLE = 0,	/* Use the existing host order (default) */
+	LOAD_BALANCE_RANDOM,		/* Randomly shuffle the hosts */
+} PGLoadBalanceType;
+
 /* Boolean value plus a not-known state, for GUCs we might have to fetch */
 typedef enum
 {
@@ -397,6 +407,7 @@ struct pg_conn
 	char	   *ssl_max_protocol_version;	/* maximum TLS protocol version */
 	char	   *target_session_attrs;	/* desired session properties */
 	char	   *require_auth;	/* name of the expected auth method */
+	char	   *load_balance_hosts; /* load balance over hosts */
 
 	/* Optional file to write trace info to */
 	FILE	   *Pfdebug;
@@ -468,6 +479,8 @@ struct pg_conn
 
 	/* Transient state needed while establishing connection */
 	PGTargetServerType target_server_type;	/* desired session properties */
+	PGLoadBalanceType load_balance_type;	/* desired load balancing
+											 * algorithm */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
 	int			naddr;			/* number of addresses returned by getaddrinfo */
@@ -487,6 +500,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index 3cd0ddb4945..80e6a15adf8 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -116,6 +116,8 @@ tests += {
     'tests': [
       't/001_uri.pl',
       't/002_api.pl',
+      't/003_load_balance_host_list.pl',
+      't/004_load_balance_dns.pl',
     ],
     'env': {'with_ssl': ssl_library},
   },
diff --git a/src/interfaces/libpq/t/003_load_balance_host_list.pl b/src/interfaces/libpq/t/003_load_balance_host_list.pl
new file mode 100644
index 00000000000..1bdddfdbcfd
--- /dev/null
+++ b/src/interfaces/libpq/t/003_load_balance_host_list.pl
@@ -0,0 +1,82 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests load balancing across the list of different hosts in the host
+# parameter of the connection string.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $node1 = PostgreSQL::Test::Cluster->new('node1');
+my $node2 = PostgreSQL::Test::Cluster->new('node2', own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# Start the tests for load balancing method 1
+my $hostlist = $node1->host . ',' . $node2->host . ',' . $node3->host;
+my $portlist = $node1->port . ',' . $node2->port . ',' . $node3->port;
+
+$node1->connect_fails(
+	"host=$hostlist port=$portlist load_balance_hosts=doesnotexist",
+	"load_balance_hosts doesn't accept unknown values",
+	expected_stderr => qr/invalid load_balance_hosts value: "doesnotexist"/);
+
+# load_balance_hosts=disable should always choose the first one.
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=disable",
+	"load_balance_hosts=disable connects to the first node",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+# Statistically the following loop with load_balance_hosts=random will almost
+# certainly connect at least once to each of the nodes. The chance of that not
+# happening is so small that it's negligible: (2/3)^50 = 1.56832855e-9
+foreach my $i (1 .. 50) {
+	$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random",
+		"seed 1234 selects node 1 first",
+		sql => "SELECT 'connect1'");
+}
+
+my $node1_occurences = () = $node1->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node2_occurences = () = $node2->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node3_occurences = () = $node3->log_content() =~ /statement: SELECT 'connect1'/g;
+
+my $total_occurences = $node1_occurences + $node2_occurences + $node3_occurences;
+
+ok($node1_occurences > 1, "expected at least one execution on node1, found $node1_occurences");
+ok($node2_occurences > 1, "expected at least one execution on node2, found $node2_occurences");
+ok($node3_occurences > 1, "expected at least one execution on node3, found $node3_occurences");
+ok($total_occurences == 50, "expected 50 executions across all nodes, found $total_occurences");
+
+$node1->stop();
+$node2->stop();
+
+# load_balance_hosts=disable should continue trying hosts until it finds a
+# working one.
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=disable",
+	"load_balance_hosts=disable continues until it connects to the a working node",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+# Also with load_balance_hosts=random we continue to the next nodes if previous
+# ones are down. Connect a few times to make sure it's not just lucky.
+foreach my $i (1 .. 5) {
+	$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random",
+		"load_balance_hosts=random continues until it connects to the a working node",
+		sql => "SELECT 'connect4'",
+		log_like => [qr/statement: SELECT 'connect4'/]);
+}
+
+done_testing();
+
diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 3e2a27fb717..a3aef8b5e91 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -2567,6 +2567,22 @@ sub issues_sql_like
 	return;
 }
 
+=pod
+
+=item $node->log_content()
+
+Returns the contents of log of the node
+
+=cut
+
+sub log_content
+{
+	my ($self) = @_;
+	return
+	  PostgreSQL::Test::Utils::slurp_file($self->logfile);
+}
+
+
 =pod
 
 =item $node->run_log(...)
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 5c5aa8bf4c9..2571d22f96d 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1702,6 +1702,7 @@ PGFileType
 PGFunction
 PGLZ_HistEntry
 PGLZ_Strategy
+PGLoadBalanceType
 PGMessageField
 PGModuleMagicFunction
 PGNoticeHooks
-- 
2.34.1

From 4f4c480a5f1342a03cbb3d525b5382d75d9054bb Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Fri, 3 Mar 2023 15:27:21 +0100
Subject: [PATCH v14 5/5] Remove unnecessary check from Fisher-Yates
 implementation

Andrey Borodin pointed out that the "undefined data check" was
unnecessary for Fisher-Yates implementations when the data that was
fetched was known to be initialized. There was one such place in the
codebase, so this removes the check there.
---
 src/backend/optimizer/geqo/geqo_recombination.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/backend/optimizer/geqo/geqo_recombination.c b/src/backend/optimizer/geqo/geqo_recombination.c
index a5d3e47ad11..53bf0cc0a42 100644
--- a/src/backend/optimizer/geqo/geqo_recombination.c
+++ b/src/backend/optimizer/geqo/geqo_recombination.c
@@ -51,9 +51,7 @@ init_tour(PlannerInfo *root, Gene *tour, int num_gene)
 	for (i = 1; i < num_gene; i++)
 	{
 		j = geqo_randint(root, i, 0);
-		/* i != j check avoids fetching uninitialized array element */
-		if (i != j)
-			tour[i] = tour[j];
+		tour[i] = tour[j];
 		tour[j] = (Gene) (i + 1);
 	}
 }
-- 
2.34.1

From 1a8f5a9b2128ddcd8bf7f60221a95db8db972962 Mon Sep 17 00:00:00 2001
From: Jelte Fennema <jelte.fennema@microsoft.com>
Date: Fri, 17 Mar 2023 09:14:02 +0100
Subject: [PATCH v14 4/5] Add DNS based libpq load balancing test

This adds a test for DNS based load balancing in libpq. This patch was a
point of discussion due the fact that it requires changing /etc/hosts
for this test to run. Thus it was removed from the main libpq load
balancing patch, and added to its own patch for further discussion.

This patch also adds tests for DNS based retries of connections of libpq,
even when load balancing is disabled. We did not have tests for that
behaviour either.
---
 .cirrus.yml                                   |  16 ++-
 doc/src/sgml/regress.sgml                     |  11 +-
 .../libpq/t/004_load_balance_dns.pl           | 122 ++++++++++++++++++
 3 files changed, 147 insertions(+), 2 deletions(-)
 create mode 100644 src/interfaces/libpq/t/004_load_balance_dns.pl

diff --git a/.cirrus.yml b/.cirrus.yml
index 505c50f3285..04786174ed4 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -25,7 +25,7 @@ env:
   MTEST_ARGS: --print-errorlogs --no-rebuild -C build
   PGCTLTIMEOUT: 120 # avoids spurious failures during parallel tests
   TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
-  PG_TEST_EXTRA: kerberos ldap ssl
+  PG_TEST_EXTRA: kerberos ldap ssl load_balance
 
 
 # What files to preserve in case tests fail
@@ -313,6 +313,14 @@ task:
     mkdir -m 770 /tmp/cores
     chown root:postgres /tmp/cores
     sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core'
+
+  setup_hosts_file_script: |
+    cat >> /etc/hosts <<-EOF
+      127.0.0.1 pg-loadbalancetest
+      127.0.0.2 pg-loadbalancetest
+      127.0.0.3 pg-loadbalancetest
+    EOF
+
   setup_additional_packages_script: |
     #apt-get update
     #DEBIAN_FRONTEND=noninteractive apt-get -y install ...
@@ -564,6 +572,12 @@ task:
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
+  setup_hosts_file_script: |
+    echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    type c:\Windows\System32\Drivers\etc\hosts
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
diff --git a/doc/src/sgml/regress.sgml b/doc/src/sgml/regress.sgml
index 719e0a76985..dd7e4a200e9 100644
--- a/doc/src/sgml/regress.sgml
+++ b/doc/src/sgml/regress.sgml
@@ -256,7 +256,7 @@ make check-world -j8 >/dev/null
    <varname>PG_TEST_EXTRA</varname> to a whitespace-separated list, for
    example:
 <programlisting>
-make check-world PG_TEST_EXTRA='kerberos ldap ssl'
+make check-world PG_TEST_EXTRA='kerberos ldap ssl load_balance'
 </programlisting>
    The following values are currently supported:
    <variablelist>
@@ -290,6 +290,15 @@ make check-world PG_TEST_EXTRA='kerberos ldap ssl'
      </listitem>
     </varlistentry>
 
+    <varlistentry>
+     <term><literal>load_balance</literal></term>
+     <listitem>
+      <para>
+       Runs the test <filename>src/interfaces/libpq/t/004_load_balance_dns.pl</filename>.  This opens TCP/IP listen sockets.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry>
      <term><literal>wal_consistency_checking</literal></term>
      <listitem>
diff --git a/src/interfaces/libpq/t/004_load_balance_dns.pl b/src/interfaces/libpq/t/004_load_balance_dns.pl
new file mode 100644
index 00000000000..a4f40510954
--- /dev/null
+++ b/src/interfaces/libpq/t/004_load_balance_dns.pl
@@ -0,0 +1,122 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests loadbalancing based on a DNS entry that contains multiple records
+# for different IPs. Since setting up a DNS server is more effort than we
+# consider reasonable to run this test, this situation is instead immitated by
+# using a hosts file where a single hostname maps to multiple different IP
+# addresses. This test requires the adminstrator to add the following lines to
+# the hosts file (if we detect that this hasn't happend we skip the test):
+#
+# 127.0.0.1 pg-loadbalancetest
+# 127.0.0.2 pg-loadbalancetest
+# 127.0.0.3 pg-loadbalancetest
+#
+# Windows or Linux are required to run this test because these OSes allow
+# binding to 127.0.0.2 and 127.0.0.3 addresess by default, but other OSes
+# don't. We need to bind to different IP addresses, so that we can use these
+# different IP addresses in the hosts file.
+#
+# The hosts file needs to be prepared before running this test. We don't do it
+# on the fly, because it requires root permissions to change the hosts file. In
+# CI we set up the previously mentioned rules in the hosts file, so that this
+# load balancing method is tested.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os;
+
+# Checks for the requirements for testing load balancing method 2
+if (!$can_bind_to_127_0_0_2) {
+	plan skip_all => "OS could not bind to 127.0.0.2"
+}
+
+my $hosts_path;
+if ($windows_os) {
+	$hosts_path = 'c:\Windows\System32\Drivers\etc\hosts';
+}
+else
+{
+	$hosts_path = '/etc/hosts';
+}
+
+my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path);
+
+if ($hosts_content !~ m/pg-loadbalancetest/) {
+	# Host file is not prepared for this test
+	plan skip_all => "hosts file was not prepared for DNS load balance test"
+}
+
+if ($ENV{PG_TEST_EXTRA} !~ /\bload_balance\b/)
+{
+	plan skip_all => 'Potentially unsafe test load_balance not enabled in PG_TEST_EXTRA';
+}
+
+$PostgreSQL::Test::Cluster::use_tcp = 1;
+$PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1';
+my $port = PostgreSQL::Test::Cluster::get_free_port();
+my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port);
+my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# load_balance_hosts=disable should always choose the first one.
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=disable",
+	"load_balance_hosts=disable connects to the first node",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+
+# Statistically the following loop with load_balance_hosts=random will almost
+# certainly connect at least once to each of the nodes. The chance of that not
+# happening is so small that it's negligible: (2/3)^50 = 1.56832855e-9
+foreach my $i (1 .. 50) {
+	$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random",
+		"seed 1234 selects node 1 first",
+		sql => "SELECT 'connect1'");
+}
+
+my $node1_occurences = () = $node1->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node2_occurences = () = $node2->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node3_occurences = () = $node3->log_content() =~ /statement: SELECT 'connect1'/g;
+
+my $total_occurences = $node1_occurences + $node2_occurences + $node3_occurences;
+
+ok($node1_occurences > 1, "expected at least one execution on node1, found $node1_occurences");
+ok($node2_occurences > 1, "expected at least one execution on node2, found $node2_occurences");
+ok($node3_occurences > 1, "expected at least one execution on node3, found $node3_occurences");
+ok($total_occurences == 50, "expected 50 executions across all nodes, found $total_occurences");
+
+$node1->stop();
+$node2->stop();
+
+# load_balance_hosts=disable should continue trying hosts until it finds a
+# working one.
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=disable",
+	"load_balance_hosts=disable continues until it connects to the a working node",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+# Also with load_balance_hosts=random we continue to the next nodes if previous
+# ones are down. Connect a few times to make sure it's not just lucky.
+foreach my $i (1 .. 5) {
+	$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random",
+		"load_balance_hosts=random continues until it connects to the a working node",
+		sql => "SELECT 'connect4'",
+		log_like => [qr/statement: SELECT 'connect4'/]);
+}
+
+done_testing();
-- 
2.34.1

From 8649f79ef6ce3aeb021f2933e93c7f7ae8a82dab Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Mon, 27 Mar 2023 11:23:13 +0200
Subject: [PATCH v15 2/2] Support connection load balancing in libpq

This adds support for load balancing connections with libpq using a
connection parameeter: load_balance_hosts=<string>. When setting the
param to random, hosts and addresses will be connected to in random
order. This then results in load balancing across these addresses and
hosts when multiple clients or frequent connection setups are used.

The randomization employed performs two leves of shuffling:

  1. The given hosts are randomly shuffled, before resolving them
     one-by-one.
  2. Once a host its addresses get resolved, the returned addresses
     are shuffled, before trying to connect to them one-by-one.

Author: Jelte Fennema <postgres@jeltef.nl>
Reviewed-by: Aleksander Alekseev <aleksander@timescale.com>
Reviewed-by: Michael Banck <mbanck@gmx.net>
Reviewed-by: Andrey Borodin <amborodin86@gmail.com>
Discussion: https://postgr.es/m/PR3PR83MB04768E2FF04818EEB2179949F7A69@PR3PR83MB0476.EURPRD83.prod.outlook.
---
 .cirrus.yml                                   |  16 ++-
 doc/src/sgml/libpq.sgml                       |  61 +++++++++
 doc/src/sgml/regress.sgml                     |  11 +-
 src/interfaces/libpq/fe-connect.c             | 103 +++++++++++++++
 src/interfaces/libpq/libpq-int.h              |  17 ++-
 src/interfaces/libpq/meson.build              |   2 +
 .../libpq/t/003_load_balance_host_list.pl     |  81 ++++++++++++
 .../libpq/t/004_load_balance_dns.pl           | 124 ++++++++++++++++++
 src/test/perl/PostgreSQL/Test/Cluster.pm      |  16 +++
 src/tools/pgindent/typedefs.list              |   1 +
 10 files changed, 429 insertions(+), 3 deletions(-)
 create mode 100644 src/interfaces/libpq/t/003_load_balance_host_list.pl
 create mode 100644 src/interfaces/libpq/t/004_load_balance_dns.pl

diff --git a/.cirrus.yml b/.cirrus.yml
index 505c50f328..04786174ed 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -25,7 +25,7 @@ env:
   MTEST_ARGS: --print-errorlogs --no-rebuild -C build
   PGCTLTIMEOUT: 120 # avoids spurious failures during parallel tests
   TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
-  PG_TEST_EXTRA: kerberos ldap ssl
+  PG_TEST_EXTRA: kerberos ldap ssl load_balance
 
 
 # What files to preserve in case tests fail
@@ -313,6 +313,14 @@ task:
     mkdir -m 770 /tmp/cores
     chown root:postgres /tmp/cores
     sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core'
+
+  setup_hosts_file_script: |
+    cat >> /etc/hosts <<-EOF
+      127.0.0.1 pg-loadbalancetest
+      127.0.0.2 pg-loadbalancetest
+      127.0.0.3 pg-loadbalancetest
+    EOF
+
   setup_additional_packages_script: |
     #apt-get update
     #DEBIAN_FRONTEND=noninteractive apt-get -y install ...
@@ -564,6 +572,12 @@ task:
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
+  setup_hosts_file_script: |
+    echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    type c:\Windows\System32\Drivers\etc\hosts
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 8579dcac95..9f72dd29d8 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -2115,6 +2115,67 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="libpq-connect-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls the order in which the client tries to connect to the available
+        hosts and addresses. Once a connection attempt is successful no other
+        hosts and addresses will be tried. This parameter is typically used in
+        combination with multiple host names or a DNS record that returns
+        multiple IPs. This parameter can be used in combination with
+        <xref linkend="libpq-connect-target-session-attrs"/>
+        to, for example, load balance over standby servers only. Once successfully
+        connected, subsequent queries on the returned connection will all be
+        sent to the same server. There are currently two modes:
+        <variablelist>
+         <varlistentry>
+          <term><literal>disable</literal> (default)</term>
+          <listitem>
+           <para>
+            No load balancing across hosts is performed.  Hosts are tried in
+            the order in which they are provided and addresses are tried in
+            the order they are received from DNS or a hosts file.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>random</literal></term>
+          <listitem>
+           <para>
+            Hosts and addresses are tried in random order. This value is mostly
+            useful when opening multiple connections at the same time, possibly
+            from different machines. This way connections can be load balanced
+            across multiple <productname>PostgreSQL</productname> servers.
+           </para>
+           <para>
+            While random load balancing, due to its random nature, will almost
+            never result in a completely uniform distribution, it statistically
+            gets quite close. One important aspect here is that this algorithm
+            uses two levels of random choices: First the hosts
+            will be resolved in random order. Then secondly, before resolving
+            the next host, all resolved addresses for the current host will be
+            tried in random order. This behaviour can skew the amount of
+            connections each node gets greatly in certain cases, for instance
+            when some hosts resolve to more addresses than others. But such a
+            skew can also be used on purpose, e.g. to increase the number of
+            connections a larger server gets by providing its hostname multiple
+            times in the host string.
+           </para>
+           <para>
+            When using this value it's recommended to also configure a reasonable
+            value for <xref linkend="libpq-connect-connect-timeout"/>. Because then,
+            if one of the nodes that are used for load balancing is not responding,
+            a new node will be tried.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
    </para>
   </sect2>
diff --git a/doc/src/sgml/regress.sgml b/doc/src/sgml/regress.sgml
index 719e0a7698..dd7e4a200e 100644
--- a/doc/src/sgml/regress.sgml
+++ b/doc/src/sgml/regress.sgml
@@ -256,7 +256,7 @@ make check-world -j8 >/dev/null
    <varname>PG_TEST_EXTRA</varname> to a whitespace-separated list, for
    example:
 <programlisting>
-make check-world PG_TEST_EXTRA='kerberos ldap ssl'
+make check-world PG_TEST_EXTRA='kerberos ldap ssl load_balance'
 </programlisting>
    The following values are currently supported:
    <variablelist>
@@ -290,6 +290,15 @@ make check-world PG_TEST_EXTRA='kerberos ldap ssl'
      </listitem>
     </varlistentry>
 
+    <varlistentry>
+     <term><literal>load_balance</literal></term>
+     <listitem>
+      <para>
+       Runs the test <filename>src/interfaces/libpq/t/004_load_balance_dns.pl</filename>.  This opens TCP/IP listen sockets.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry>
      <term><literal>wal_consistency_checking</literal></term>
      <listitem>
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 662ef08857..ca2fcc576d 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -123,6 +123,7 @@ static int	ldapServiceLookup(const char *purl, PQconninfoOption *options,
 #define DefaultChannelBinding	"disable"
 #endif
 #define DefaultTargetSessionAttrs	"any"
+#define DefaultLoadBalanceHosts	"disable"
 #ifdef USE_SSL
 #define DefaultSSLMode "prefer"
 #define DefaultSSLCertMode "allow"
@@ -351,6 +352,11 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Target-Session-Attrs", "", 15, /* sizeof("prefer-standby") = 15 */
 	offsetof(struct pg_conn, target_session_attrs)},
 
+	{"load_balance_hosts", "PGLOADBALANCEHOSTS",
+		DefaultLoadBalanceHosts, NULL,
+		"Load-Balance-Hosts", "", 8,	/* sizeof("disable") = 8 */
+	offsetof(struct pg_conn, load_balance_hosts)},
+
 	/* Terminating entry --- MUST BE LAST */
 	{NULL, NULL, NULL, NULL,
 	NULL, NULL, 0}
@@ -435,6 +441,8 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static bool parse_int_param(const char *value, int *result, PGconn *conn,
+							const char *context);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1020,6 +1028,31 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on the connection address,
+ * timestamp and PID.
+ */
+static void
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		struct timeval tval = {0};
+
+		gettimeofday(&tval, NULL);
+
+		rseed = ((uint64) conn) ^
+			((uint64) getpid()) ^
+			((uint64) tval.tv_usec) ^
+			((uint64) tval.tv_sec);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+}
+
 /*
  *		connectOptions2
  *
@@ -1619,6 +1652,49 @@ connectOptions2(PGconn *conn)
 	else
 		conn->target_server_type = SERVER_TYPE_ANY;
 
+	/*
+	 * validate load_balance_hosts option, and set load_balance_type
+	 */
+	if (conn->load_balance_hosts)
+	{
+		if (strcmp(conn->load_balance_hosts, "disable") == 0)
+			conn->load_balance_type = LOAD_BALANCE_DISABLE;
+		else if (strcmp(conn->load_balance_hosts, "random") == 0)
+			conn->load_balance_type = LOAD_BALANCE_RANDOM;
+		else
+		{
+			conn->status = CONNECTION_BAD;
+			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
+									"load_balance_hosts",
+									conn->load_balance_hosts);
+			return false;
+		}
+	}
+	else
+		conn->load_balance_type = LOAD_BALANCE_DISABLE;
+
+	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+	{
+		libpq_prng_init(conn);
+
+		/*
+		 * This is the "inside-out" variant of the Fisher-Yates shuffle
+		 * algorithm. Notionally, we append each new value to the array and
+		 * then swap it with a randomly-chosen array element (possibly
+		 * including itself, else we fail to generate permutations with the
+		 * last integer last).  The swap step can be optimized by combining it
+		 * with the insertion.
+		 */
+		for (i = 1; i < conn->nconnhost; i++)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
 	/*
 	 * Resolve special "auto" client_encoding from the locale
 	 */
@@ -2624,6 +2700,32 @@ keep_going:						/* We will come back to here until there is
 		ret = store_conn_addrinfo(conn, addrlist);
 		pg_freeaddrinfo_all(hint.ai_family, addrlist);
 
+		/*
+		 * If random load balancing is enabled we shuffle the addresses.
+		 */
+		if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+		{
+			/*
+			 * This is the "inside-out" variant of the Fisher-Yates shuffle
+			 * algorithm. Notionally, we append each new value to the array
+			 * and then swap it with a randomly-chosen array element (possibly
+			 * including itself, else we fail to generate permutations with
+			 * the last integer last).  The swap step can be optimized by
+			 * combining it with the insertion.
+			 *
+			 * We don't need to initialize conn->prng_state here, because that
+			 * already happened in connectOptions2.
+			 */
+			for (int i = 1; i < conn->naddr; i++)
+			{
+				int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+				AddrInfo	temp = conn->addr[j];
+
+				conn->addr[j] = conn->addr[i];
+				conn->addr[i] = temp;
+			}
+		}
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -4318,6 +4420,7 @@ freePGconn(PGconn *conn)
 	free(conn->outBuffer);
 	free(conn->rowBuf);
 	free(conn->target_session_attrs);
+	free(conn->load_balance_hosts);
 	termPQExpBuffer(&conn->errorMessage);
 	termPQExpBuffer(&conn->workBuffer);
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 7d09147525..d93e976ca5 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -26,7 +26,8 @@
 #include <netdb.h>
 #include <sys/socket.h>
 #include <time.h>
-#ifndef WIN32
+/* MinGW has sys/time.h, but MSVC doesn't */
+#ifndef _MSC_VER
 #include <sys/time.h>
 #endif
 
@@ -82,6 +83,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -242,6 +245,13 @@ typedef enum
 	SERVER_TYPE_PREFER_STANDBY_PASS2	/* second pass - behaves same as ANY */
 } PGTargetServerType;
 
+/* Target server type (decoded value of load_balance_hosts) */
+typedef enum
+{
+	LOAD_BALANCE_DISABLE = 0,	/* Use the existing host order (default) */
+	LOAD_BALANCE_RANDOM,		/* Randomly shuffle the hosts */
+} PGLoadBalanceType;
+
 /* Boolean value plus a not-known state, for GUCs we might have to fetch */
 typedef enum
 {
@@ -398,6 +408,7 @@ struct pg_conn
 	char	   *ssl_max_protocol_version;	/* maximum TLS protocol version */
 	char	   *target_session_attrs;	/* desired session properties */
 	char	   *require_auth;	/* name of the expected auth method */
+	char	   *load_balance_hosts; /* load balance over hosts */
 
 	/* Optional file to write trace info to */
 	FILE	   *Pfdebug;
@@ -469,6 +480,8 @@ struct pg_conn
 
 	/* Transient state needed while establishing connection */
 	PGTargetServerType target_server_type;	/* desired session properties */
+	PGLoadBalanceType load_balance_type;	/* desired load balancing
+											 * algorithm */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
 	int			naddr;			/* number of addresses returned by getaddrinfo */
@@ -488,6 +501,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index 3cd0ddb494..80e6a15adf 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -116,6 +116,8 @@ tests += {
     'tests': [
       't/001_uri.pl',
       't/002_api.pl',
+      't/003_load_balance_host_list.pl',
+      't/004_load_balance_dns.pl',
     ],
     'env': {'with_ssl': ssl_library},
   },
diff --git a/src/interfaces/libpq/t/003_load_balance_host_list.pl b/src/interfaces/libpq/t/003_load_balance_host_list.pl
new file mode 100644
index 0000000000..bda3d0c97a
--- /dev/null
+++ b/src/interfaces/libpq/t/003_load_balance_host_list.pl
@@ -0,0 +1,81 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests load balancing across the list of different hosts in the host
+# parameter of the connection string.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $node1 = PostgreSQL::Test::Cluster->new('node1');
+my $node2 = PostgreSQL::Test::Cluster->new('node2', own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# Start the tests for load balancing method 1
+my $hostlist = $node1->host . ',' . $node2->host . ',' . $node3->host;
+my $portlist = $node1->port . ',' . $node2->port . ',' . $node3->port;
+
+$node1->connect_fails(
+	"host=$hostlist port=$portlist load_balance_hosts=doesnotexist",
+	"load_balance_hosts doesn't accept unknown values",
+	expected_stderr => qr/invalid load_balance_hosts value: "doesnotexist"/);
+
+# load_balance_hosts=disable should always choose the first one.
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=disable",
+	"load_balance_hosts=disable connects to the first node",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+# Statistically the following loop with load_balance_hosts=random will almost
+# certainly connect at least once to each of the nodes. The chance of that not
+# happening is so small that it's negligible: (2/3)^50 = 1.56832855e-9
+foreach my $i (1 .. 50) {
+	$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random",
+		"repeated connections with random load balancing",
+		sql => "SELECT 'connect1'");
+}
+
+my $node1_occurences = () = $node1->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node2_occurences = () = $node2->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node3_occurences = () = $node3->log_content() =~ /statement: SELECT 'connect1'/g;
+
+my $total_occurences = $node1_occurences + $node2_occurences + $node3_occurences;
+
+ok($node1_occurences > 1, "expected at least one execution on node1, found none");
+ok($node2_occurences > 1, "expected at least one execution on node2, found none");
+ok($node3_occurences > 1, "expected at least one execution on node3, found none");
+ok($total_occurences == 50, "expected 50 executions across all nodes, found $total_occurences");
+
+$node1->stop();
+$node2->stop();
+
+# load_balance_hosts=disable should continue trying hosts until it finds a
+# working one.
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=disable",
+	"load_balance_hosts=disable continues until it connects to the a working node",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+# Also with load_balance_hosts=random we continue to the next nodes if previous
+# ones are down. Connect a few times to make sure it's not just lucky.
+foreach my $i (1 .. 5) {
+	$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random",
+		"load_balance_hosts=random continues until it connects to the a working node",
+		sql => "SELECT 'connect4'",
+		log_like => [qr/statement: SELECT 'connect4'/]);
+}
+
+done_testing();
diff --git a/src/interfaces/libpq/t/004_load_balance_dns.pl b/src/interfaces/libpq/t/004_load_balance_dns.pl
new file mode 100644
index 0000000000..9cd9b812cf
--- /dev/null
+++ b/src/interfaces/libpq/t/004_load_balance_dns.pl
@@ -0,0 +1,124 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+if ($ENV{PG_TEST_EXTRA} !~ /\bload_balance\b/)
+{
+	plan skip_all =>
+	  'Potentially unsafe test load_balance not enabled in PG_TEST_EXTRA';
+}
+
+# This tests loadbalancing based on a DNS entry that contains multiple records
+# for different IPs. Since setting up a DNS server is more effort than we
+# consider reasonable to run this test, this situation is instead immitated by
+# using a hosts file where a single hostname maps to multiple different IP
+# addresses. This test requires the adminstrator to add the following lines to
+# the hosts file (if we detect that this hasn't happend we skip the test):
+#
+# 127.0.0.1 pg-loadbalancetest
+# 127.0.0.2 pg-loadbalancetest
+# 127.0.0.3 pg-loadbalancetest
+#
+# Windows or Linux are required to run this test because these OSes allow
+# binding to 127.0.0.2 and 127.0.0.3 addresess by default, but other OSes
+# don't. We need to bind to different IP addresses, so that we can use these
+# different IP addresses in the hosts file.
+#
+# The hosts file needs to be prepared before running this test. We don't do it
+# on the fly, because it requires root permissions to change the hosts file. In
+# CI we set up the previously mentioned rules in the hosts file, so that this
+# load balancing method is tested.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os;
+
+# Checks for the requirements for testing load balancing method 2
+if (!$can_bind_to_127_0_0_2) {
+	plan skip_all => 'load_balance test only supported on Linux and Windows';
+}
+
+my $hosts_path;
+if ($windows_os) {
+	$hosts_path = 'c:\Windows\System32\Drivers\etc\hosts';
+}
+else
+{
+	$hosts_path = '/etc/hosts';
+}
+
+my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path);
+
+my $hosts_count = () = $hosts_content =~ /127\.0\.0\.[1-3] pg-loadbalancetest/g;
+if ($hosts_count != 3) {
+	# Host file is not prepared for this test
+	plan skip_all => "hosts file was not prepared for DNS load balance test"
+}
+
+$PostgreSQL::Test::Cluster::use_tcp = 1;
+$PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1';
+my $port = PostgreSQL::Test::Cluster::get_free_port();
+my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port);
+my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# load_balance_hosts=disable should always choose the first one.
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=disable",
+	"load_balance_hosts=disable connects to the first node",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+
+# Statistically the following loop with load_balance_hosts=random will almost
+# certainly connect at least once to each of the nodes. The chance of that not
+# happening is so small that it's negligible: (2/3)^50 = 1.56832855e-9
+foreach my $i (1 .. 50) {
+	$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random",
+		"repeated connections with random load balancing",
+		sql => "SELECT 'connect1'");
+}
+
+my $node1_occurences = () = $node1->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node2_occurences = () = $node2->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node3_occurences = () = $node3->log_content() =~ /statement: SELECT 'connect1'/g;
+
+my $total_occurences = $node1_occurences + $node2_occurences + $node3_occurences;
+
+ok($node1_occurences > 1, "expected at least one connection on node1, found none");
+ok($node2_occurences > 1, "expected at least one connection on node2, found none");
+ok($node3_occurences > 1, "expected at least one connection on node3, found none");
+ok($total_occurences == 50, "expected 50 executions across all nodes, found $total_occurences");
+
+$node1->stop();
+$node2->stop();
+
+# load_balance_hosts=disable should continue trying hosts until it finds a
+# working one.
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=disable",
+	"load_balance_hosts=disable continues until it connects to the a working node",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+# Also with load_balance_hosts=random we continue to the next nodes if previous
+# ones are down. Connect a few times to make sure it's not just lucky.
+foreach my $i (1 .. 5) {
+	$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random",
+		"load_balance_hosts=random continues until it connects to the a working node",
+		sql => "SELECT 'connect4'",
+		log_like => [qr/statement: SELECT 'connect4'/]);
+}
+
+done_testing();
diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 3e2a27fb71..a3aef8b5e9 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -2567,6 +2567,22 @@ sub issues_sql_like
 	return;
 }
 
+=pod
+
+=item $node->log_content()
+
+Returns the contents of log of the node
+
+=cut
+
+sub log_content
+{
+	my ($self) = @_;
+	return
+	  PostgreSQL::Test::Utils::slurp_file($self->logfile);
+}
+
+
 =pod
 
 =item $node->run_log(...)
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index dfa1e309ee..86a3f8160f 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1704,6 +1704,7 @@ PGFileType
 PGFunction
 PGLZ_HistEntry
 PGLZ_Strategy
+PGLoadBalanceType
 PGMessageField
 PGModuleMagicFunction
 PGNoticeHooks
-- 
2.32.1 (Apple Git-133)

From 2bd790d6d30e69e86909ce50831191914a59dec5 Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Mon, 27 Mar 2023 11:17:56 +0200
Subject: [PATCH v15 1/2] Copy and store addrinfo in libpq-owned private memory

This refactors libpq to copy addrinfos returned by getaddrinfo to
memory owned by libpq such that future improvements can alter for
example ther order of entries.

As a nice side effect of this refactor the is that mechanism for
iteration over addresses in PQconnectPoll is now identical to its
iteration over hosts.

Author: Jelte Fennema <postgres@jeltef.nl>
Reviewed-by: Aleksander Alekseev <aleksander@timescale.com>
Reviewed-by: Michael Banck <mbanck@gmx.net>
Reviewed-by: Andrey Borodin <amborodin86@gmail.com>
Discussion: https://postgr.es/m/PR3PR83MB04768E2FF04818EEB2179949F7A69@PR3PR83MB0476.EURPRD83.prod.outlook.com
---
 src/include/libpq/pqcomm.h        |   6 ++
 src/interfaces/libpq/fe-connect.c | 110 +++++++++++++++++++++---------
 src/interfaces/libpq/libpq-int.h  |   7 +-
 src/tools/pgindent/typedefs.list  |   1 +
 4 files changed, 90 insertions(+), 34 deletions(-)

diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index bff7dd18a2..c85090259d 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+} AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index b71378d94c..662ef08857 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -389,6 +389,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static int	store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *connstr,
@@ -2295,7 +2296,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2339,11 +2340,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2490,9 +2491,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2505,6 +2506,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2545,7 +2547,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2568,8 +2570,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
 											ch->host, gai_strerror(ret));
@@ -2580,8 +2582,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
 											ch->hostaddr, gai_strerror(ret));
@@ -2590,7 +2592,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2605,8 +2607,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
 											portstr, gai_strerror(ret));
@@ -2615,8 +2617,13 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		/*
+		 * Store a copy of the addrlist in private memory so we can perform
+		 * randomization for load balancing.
+		 */
+		ret = store_conn_addrinfo(conn, addrlist);
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2673,31 +2680,30 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
 					int			sock_type;
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2732,7 +2738,7 @@ keep_going:						/* We will come back to here until there is
 					 */
 					sock_type |= SOCK_NONBLOCK;
 #endif
-					conn->sock = socket(addr_cur->ai_family, sock_type, 0);
+					conn->sock = socket(addr_cur->family, sock_type, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2743,7 +2749,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2769,7 +2775,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2800,7 +2806,7 @@ keep_going:						/* We will come back to here until there is
 #endif							/* F_SETFD */
 #endif
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2892,8 +2898,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4318,6 +4324,49 @@ freePGconn(PGconn *conn)
 	free(conn);
 }
 
+/*
+ * store_conn_addrinfo
+ *	 - copy addrinfo to PGconn object
+ *
+ * Copies the addrinfos from addrlist to the PGconn object such that the
+ * addrinfos can be manipulated by libpq. Returns a positive integer on
+ * failure, otherwise zero.
+ */
+static int
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+	{
+		libpq_append_conn_error(conn, "out of memory");
+		return 1;
+	}
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	return 0;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4325,11 +4374,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 88b9838d76..7d09147525 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -471,9 +471,10 @@ struct pg_conn
 	PGTargetServerType target_server_type;	/* desired session properties */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
-	int			addrlist_family;	/* needed to know how to free addrlist */
+	int			naddr;			/* number of addresses returned by getaddrinfo */
+	int			whichaddr;		/* the address currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	bool		send_appname;	/* okay to send application_name? */
 
 	/* Miscellaneous stuff */
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 0b7bc45767..dfa1e309ee 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -26,6 +26,7 @@ AcquireSampleRowsFunc
 ActionList
 ActiveSnapshotElt
 AddForeignUpdateTargets_function
+AddrInfo
 AffixNode
 AffixNodeData
 AfterTriggerEvent
-- 
2.32.1 (Apple Git-133)

From 4177f8fa552716268ac2ad69448eb6aa984fce95 Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Mon, 27 Mar 2023 11:17:56 +0200
Subject: [PATCH v16 1/2] Copy and store addrinfo in libpq-owned private memory

This refactors libpq to copy addrinfos returned by getaddrinfo to
memory owned by libpq such that future improvements can alter for
example the order of entries.

As a nice side effect of this refactor the mechanism for iteration
over addresses in PQconnectPoll is now identical to its iteration
over hosts.

Author: Jelte Fennema <postgres@jeltef.nl>
Reviewed-by: Aleksander Alekseev <aleksander@timescale.com>
Reviewed-by: Michael Banck <mbanck@gmx.net>
Reviewed-by: Andrey Borodin <amborodin86@gmail.com>
Discussion: https://postgr.es/m/PR3PR83MB04768E2FF04818EEB2179949F7A69@PR3PR83MB0476.EURPRD83.prod.outlook.com
---
 src/include/libpq/pqcomm.h        |   6 ++
 src/interfaces/libpq/fe-connect.c | 112 +++++++++++++++++++++---------
 src/interfaces/libpq/libpq-int.h  |   7 +-
 src/tools/pgindent/typedefs.list  |   1 +
 4 files changed, 92 insertions(+), 34 deletions(-)

diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h
index bff7dd18a23..c85090259d9 100644
--- a/src/include/libpq/pqcomm.h
+++ b/src/include/libpq/pqcomm.h
@@ -27,6 +27,12 @@ typedef struct
 	socklen_t	salen;
 } SockAddr;
 
+typedef struct
+{
+	int			family;
+	SockAddr	addr;
+} AddrInfo;
+
 /* Configure the UNIX socket location for the well known port. */
 
 #define UNIXSOCK_PATH(path, port, sockdir) \
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index b71378d94c5..4e798e1672c 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -389,6 +389,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static void release_conn_addrinfo(PGconn *conn);
+static int	store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist);
 static void sendTerminateConn(PGconn *conn);
 static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage);
 static PQconninfoOption *parse_connection_string(const char *connstr,
@@ -2295,7 +2296,7 @@ connectDBComplete(PGconn *conn)
 	time_t		finish_time = ((time_t) -1);
 	int			timeout = 0;
 	int			last_whichhost = -2;	/* certainly different from whichhost */
-	struct addrinfo *last_addr_cur = NULL;
+	int			last_whichaddr = -2;	/* certainly different from whichaddr */
 
 	if (conn == NULL || conn->status == CONNECTION_BAD)
 		return 0;
@@ -2339,11 +2340,11 @@ connectDBComplete(PGconn *conn)
 		if (flag != PGRES_POLLING_OK &&
 			timeout > 0 &&
 			(conn->whichhost != last_whichhost ||
-			 conn->addr_cur != last_addr_cur))
+			 conn->whichaddr != last_whichaddr))
 		{
 			finish_time = time(NULL) + timeout;
 			last_whichhost = conn->whichhost;
-			last_addr_cur = conn->addr_cur;
+			last_whichaddr = conn->whichaddr;
 		}
 
 		/*
@@ -2490,9 +2491,9 @@ keep_going:						/* We will come back to here until there is
 	/* Time to advance to next address, or next host if no more addresses? */
 	if (conn->try_next_addr)
 	{
-		if (conn->addr_cur && conn->addr_cur->ai_next)
+		if (conn->whichaddr < conn->naddr)
 		{
-			conn->addr_cur = conn->addr_cur->ai_next;
+			conn->whichaddr++;
 			reset_connection_state_machine = true;
 		}
 		else
@@ -2505,6 +2506,7 @@ keep_going:						/* We will come back to here until there is
 	{
 		pg_conn_host *ch;
 		struct addrinfo hint;
+		struct addrinfo *addrlist;
 		int			thisport;
 		int			ret;
 		char		portstr[MAXPGPATH];
@@ -2545,7 +2547,7 @@ keep_going:						/* We will come back to here until there is
 		/* Initialize hint structure */
 		MemSet(&hint, 0, sizeof(hint));
 		hint.ai_socktype = SOCK_STREAM;
-		conn->addrlist_family = hint.ai_family = AF_UNSPEC;
+		hint.ai_family = AF_UNSPEC;
 
 		/* Figure out the port number we're going to use. */
 		if (ch->port == NULL || ch->port[0] == '\0')
@@ -2568,8 +2570,8 @@ keep_going:						/* We will come back to here until there is
 		{
 			case CHT_HOST_NAME:
 				ret = pg_getaddrinfo_all(ch->host, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s",
 											ch->host, gai_strerror(ret));
@@ -2580,8 +2582,8 @@ keep_going:						/* We will come back to here until there is
 			case CHT_HOST_ADDRESS:
 				hint.ai_flags = AI_NUMERICHOST;
 				ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not parse network address \"%s\": %s",
 											ch->hostaddr, gai_strerror(ret));
@@ -2590,7 +2592,7 @@ keep_going:						/* We will come back to here until there is
 				break;
 
 			case CHT_UNIX_SOCKET:
-				conn->addrlist_family = hint.ai_family = AF_UNIX;
+				hint.ai_family = AF_UNIX;
 				UNIXSOCK_PATH(portstr, thisport, ch->host);
 				if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN)
 				{
@@ -2605,8 +2607,8 @@ keep_going:						/* We will come back to here until there is
 				 * name as a Unix-domain socket path.
 				 */
 				ret = pg_getaddrinfo_all(NULL, portstr, &hint,
-										 &conn->addrlist);
-				if (ret || !conn->addrlist)
+										 &addrlist);
+				if (ret || !addrlist)
 				{
 					libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s",
 											portstr, gai_strerror(ret));
@@ -2615,8 +2617,15 @@ keep_going:						/* We will come back to here until there is
 				break;
 		}
 
-		/* OK, scan this addrlist for a working server address */
-		conn->addr_cur = conn->addrlist;
+		/*
+		 * Store a copy of the addrlist in private memory so we can perform
+		 * randomization for load balancing.
+		 */
+		ret = store_conn_addrinfo(conn, addrlist);
+		pg_freeaddrinfo_all(hint.ai_family, addrlist);
+		if (ret)
+			goto error_return;	/* message already logged */
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -2673,31 +2682,30 @@ keep_going:						/* We will come back to here until there is
 			{
 				/*
 				 * Try to initiate a connection to one of the addresses
-				 * returned by pg_getaddrinfo_all().  conn->addr_cur is the
+				 * returned by pg_getaddrinfo_all().  conn->whichaddr is the
 				 * next one to try.
 				 *
 				 * The extra level of braces here is historical.  It's not
 				 * worth reindenting this whole switch case to remove 'em.
 				 */
 				{
-					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
 					int			sock_type;
+					AddrInfo   *addr_cur;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
 					 * the addresses for the current host.
 					 */
-					if (addr_cur == NULL)
+					if (conn->whichaddr == conn->naddr)
 					{
 						conn->try_next_host = true;
 						goto keep_going;
 					}
+					addr_cur = &conn->addr[conn->whichaddr];
 
 					/* Remember current address for possible use later */
-					memcpy(&conn->raddr.addr, addr_cur->ai_addr,
-						   addr_cur->ai_addrlen);
-					conn->raddr.salen = addr_cur->ai_addrlen;
+					memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr));
 
 					/*
 					 * Set connip, too.  Note we purposely ignore strdup
@@ -2732,7 +2740,7 @@ keep_going:						/* We will come back to here until there is
 					 */
 					sock_type |= SOCK_NONBLOCK;
 #endif
-					conn->sock = socket(addr_cur->ai_family, sock_type, 0);
+					conn->sock = socket(addr_cur->family, sock_type, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2743,7 +2751,7 @@ keep_going:						/* We will come back to here until there is
 						 * cases where the address list includes both IPv4 and
 						 * IPv6 but kernel only accepts one family.
 						 */
-						if (addr_cur->ai_next != NULL ||
+						if (conn->whichaddr < conn->naddr ||
 							conn->whichhost + 1 < conn->nconnhost)
 						{
 							conn->try_next_addr = true;
@@ -2769,7 +2777,7 @@ keep_going:						/* We will come back to here until there is
 					 * TCP sockets, nonblock mode, close-on-exec.  Try the
 					 * next address if any of this fails.
 					 */
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 						if (!connectNoDelay(conn))
 						{
@@ -2800,7 +2808,7 @@ keep_going:						/* We will come back to here until there is
 #endif							/* F_SETFD */
 #endif
 
-					if (addr_cur->ai_family != AF_UNIX)
+					if (addr_cur->family != AF_UNIX)
 					{
 #ifndef WIN32
 						int			on = 1;
@@ -2892,8 +2900,8 @@ keep_going:						/* We will come back to here until there is
 					 * Start/make connection.  This should not block, since we
 					 * are in nonblock mode.  If it does, well, too bad.
 					 */
-					if (connect(conn->sock, addr_cur->ai_addr,
-								addr_cur->ai_addrlen) < 0)
+					if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr,
+								addr_cur->addr.salen) < 0)
 					{
 						if (SOCK_ERRNO == EINPROGRESS ||
 #ifdef WIN32
@@ -4318,6 +4326,49 @@ freePGconn(PGconn *conn)
 	free(conn);
 }
 
+/*
+ * store_conn_addrinfo
+ *	 - copy addrinfo to PGconn object
+ *
+ * Copies the addrinfos from addrlist to the PGconn object such that the
+ * addrinfos can be manipulated by libpq. Returns a positive integer on
+ * failure, otherwise zero.
+ */
+static int
+store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist)
+{
+	struct addrinfo *ai = addrlist;
+
+	conn->whichaddr = 0;
+
+	conn->naddr = 0;
+	while (ai)
+	{
+		ai = ai->ai_next;
+		conn->naddr++;
+	}
+
+	conn->addr = calloc(conn->naddr, sizeof(AddrInfo));
+	if (conn->addr == NULL)
+	{
+		libpq_append_conn_error(conn, "out of memory");
+		return 1;
+	}
+
+	ai = addrlist;
+	for (int i = 0; i < conn->naddr; i++)
+	{
+		conn->addr[i].family = ai->ai_family;
+
+		memcpy(&conn->addr[i].addr.addr, ai->ai_addr,
+			   ai->ai_addrlen);
+		conn->addr[i].addr.salen = ai->ai_addrlen;
+		ai = ai->ai_next;
+	}
+
+	return 0;
+}
+
 /*
  * release_conn_addrinfo
  *	 - Free any addrinfo list in the PGconn.
@@ -4325,11 +4376,10 @@ freePGconn(PGconn *conn)
 static void
 release_conn_addrinfo(PGconn *conn)
 {
-	if (conn->addrlist)
+	if (conn->addr)
 	{
-		pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist);
-		conn->addrlist = NULL;
-		conn->addr_cur = NULL;	/* for safety */
+		free(conn->addr);
+		conn->addr = NULL;
 	}
 }
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 88b9838d766..7d091475255 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -471,9 +471,10 @@ struct pg_conn
 	PGTargetServerType target_server_type;	/* desired session properties */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
-	struct addrinfo *addrlist;	/* list of addresses for current connhost */
-	struct addrinfo *addr_cur;	/* the one currently being tried */
-	int			addrlist_family;	/* needed to know how to free addrlist */
+	int			naddr;			/* number of addresses returned by getaddrinfo */
+	int			whichaddr;		/* the address currently being tried */
+	AddrInfo   *addr;			/* the array of addresses for the currently
+								 * tried host */
 	bool		send_appname;	/* okay to send application_name? */
 
 	/* Miscellaneous stuff */
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 0b7bc457671..dfa1e309ee3 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -26,6 +26,7 @@ AcquireSampleRowsFunc
 ActionList
 ActiveSnapshotElt
 AddForeignUpdateTargets_function
+AddrInfo
 AffixNode
 AffixNodeData
 AfterTriggerEvent

base-commit: 4c8d654084700f801f48827bb3531a6779b8b90e
-- 
2.34.1

From dc825d39752fcd0698846839ef208fa0b8c77bad Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Mon, 27 Mar 2023 11:23:13 +0200
Subject: [PATCH v16 2/2] Support connection load balancing in libpq

This adds support for load balancing connections with libpq using a
connection parameter: load_balance_hosts=<string>. When setting the
param to random, hosts and addresses will be connected to in random
order. This then results in load balancing across these addresses and
hosts when multiple clients or frequent connection setups are used.

The randomization employed performs two levels of shuffling:

  1. The given hosts are randomly shuffled, before resolving them
     one-by-one.
  2. Once a host its addresses get resolved, the returned addresses
     are shuffled, before trying to connect to them one-by-one.

Author: Jelte Fennema <postgres@jeltef.nl>
Reviewed-by: Aleksander Alekseev <aleksander@timescale.com>
Reviewed-by: Michael Banck <mbanck@gmx.net>
Reviewed-by: Andrey Borodin <amborodin86@gmail.com>
Discussion: https://postgr.es/m/PR3PR83MB04768E2FF04818EEB2179949F7A69@PR3PR83MB0476.EURPRD83.prod.outlook.
---
 .cirrus.yml                                   |  16 ++-
 doc/src/sgml/libpq.sgml                       |  61 +++++++++
 doc/src/sgml/regress.sgml                     |  11 +-
 src/interfaces/libpq/fe-connect.c             | 103 +++++++++++++++
 src/interfaces/libpq/libpq-int.h              |  17 ++-
 src/interfaces/libpq/meson.build              |   2 +
 .../libpq/t/003_load_balance_host_list.pl     |  81 ++++++++++++
 .../libpq/t/004_load_balance_dns.pl           | 124 ++++++++++++++++++
 src/test/perl/PostgreSQL/Test/Cluster.pm      |  16 +++
 src/tools/pgindent/typedefs.list              |   1 +
 10 files changed, 429 insertions(+), 3 deletions(-)
 create mode 100644 src/interfaces/libpq/t/003_load_balance_host_list.pl
 create mode 100644 src/interfaces/libpq/t/004_load_balance_dns.pl

diff --git a/.cirrus.yml b/.cirrus.yml
index 505c50f3285..04786174ed4 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -25,7 +25,7 @@ env:
   MTEST_ARGS: --print-errorlogs --no-rebuild -C build
   PGCTLTIMEOUT: 120 # avoids spurious failures during parallel tests
   TEMP_CONFIG: ${CIRRUS_WORKING_DIR}/src/tools/ci/pg_ci_base.conf
-  PG_TEST_EXTRA: kerberos ldap ssl
+  PG_TEST_EXTRA: kerberos ldap ssl load_balance
 
 
 # What files to preserve in case tests fail
@@ -313,6 +313,14 @@ task:
     mkdir -m 770 /tmp/cores
     chown root:postgres /tmp/cores
     sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core'
+
+  setup_hosts_file_script: |
+    cat >> /etc/hosts <<-EOF
+      127.0.0.1 pg-loadbalancetest
+      127.0.0.2 pg-loadbalancetest
+      127.0.0.3 pg-loadbalancetest
+    EOF
+
   setup_additional_packages_script: |
     #apt-get update
     #DEBIAN_FRONTEND=noninteractive apt-get -y install ...
@@ -564,6 +572,12 @@ task:
   setup_additional_packages_script: |
     REM choco install -y --no-progress ...
 
+  setup_hosts_file_script: |
+    echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts
+    type c:\Windows\System32\Drivers\etc\hosts
+
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 8579dcac952..9f72dd29d89 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -2115,6 +2115,67 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="libpq-connect-load-balance-hosts" xreflabel="load_balance_hosts">
+      <term><literal>load_balance_hosts</literal></term>
+      <listitem>
+       <para>
+        Controls the order in which the client tries to connect to the available
+        hosts and addresses. Once a connection attempt is successful no other
+        hosts and addresses will be tried. This parameter is typically used in
+        combination with multiple host names or a DNS record that returns
+        multiple IPs. This parameter can be used in combination with
+        <xref linkend="libpq-connect-target-session-attrs"/>
+        to, for example, load balance over standby servers only. Once successfully
+        connected, subsequent queries on the returned connection will all be
+        sent to the same server. There are currently two modes:
+        <variablelist>
+         <varlistentry>
+          <term><literal>disable</literal> (default)</term>
+          <listitem>
+           <para>
+            No load balancing across hosts is performed.  Hosts are tried in
+            the order in which they are provided and addresses are tried in
+            the order they are received from DNS or a hosts file.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry>
+          <term><literal>random</literal></term>
+          <listitem>
+           <para>
+            Hosts and addresses are tried in random order. This value is mostly
+            useful when opening multiple connections at the same time, possibly
+            from different machines. This way connections can be load balanced
+            across multiple <productname>PostgreSQL</productname> servers.
+           </para>
+           <para>
+            While random load balancing, due to its random nature, will almost
+            never result in a completely uniform distribution, it statistically
+            gets quite close. One important aspect here is that this algorithm
+            uses two levels of random choices: First the hosts
+            will be resolved in random order. Then secondly, before resolving
+            the next host, all resolved addresses for the current host will be
+            tried in random order. This behaviour can skew the amount of
+            connections each node gets greatly in certain cases, for instance
+            when some hosts resolve to more addresses than others. But such a
+            skew can also be used on purpose, e.g. to increase the number of
+            connections a larger server gets by providing its hostname multiple
+            times in the host string.
+           </para>
+           <para>
+            When using this value it's recommended to also configure a reasonable
+            value for <xref linkend="libpq-connect-connect-timeout"/>. Because then,
+            if one of the nodes that are used for load balancing is not responding,
+            a new node will be tried.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
    </para>
   </sect2>
diff --git a/doc/src/sgml/regress.sgml b/doc/src/sgml/regress.sgml
index 719e0a76985..dd7e4a200e9 100644
--- a/doc/src/sgml/regress.sgml
+++ b/doc/src/sgml/regress.sgml
@@ -256,7 +256,7 @@ make check-world -j8 >/dev/null
    <varname>PG_TEST_EXTRA</varname> to a whitespace-separated list, for
    example:
 <programlisting>
-make check-world PG_TEST_EXTRA='kerberos ldap ssl'
+make check-world PG_TEST_EXTRA='kerberos ldap ssl load_balance'
 </programlisting>
    The following values are currently supported:
    <variablelist>
@@ -290,6 +290,15 @@ make check-world PG_TEST_EXTRA='kerberos ldap ssl'
      </listitem>
     </varlistentry>
 
+    <varlistentry>
+     <term><literal>load_balance</literal></term>
+     <listitem>
+      <para>
+       Runs the test <filename>src/interfaces/libpq/t/004_load_balance_dns.pl</filename>.  This opens TCP/IP listen sockets.
+      </para>
+     </listitem>
+    </varlistentry>
+
     <varlistentry>
      <term><literal>wal_consistency_checking</literal></term>
      <listitem>
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 4e798e1672c..75522c7d191 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -123,6 +123,7 @@ static int	ldapServiceLookup(const char *purl, PQconninfoOption *options,
 #define DefaultChannelBinding	"disable"
 #endif
 #define DefaultTargetSessionAttrs	"any"
+#define DefaultLoadBalanceHosts	"disable"
 #ifdef USE_SSL
 #define DefaultSSLMode "prefer"
 #define DefaultSSLCertMode "allow"
@@ -351,6 +352,11 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Target-Session-Attrs", "", 15, /* sizeof("prefer-standby") = 15 */
 	offsetof(struct pg_conn, target_session_attrs)},
 
+	{"load_balance_hosts", "PGLOADBALANCEHOSTS",
+		DefaultLoadBalanceHosts, NULL,
+		"Load-Balance-Hosts", "", 8,	/* sizeof("disable") = 8 */
+	offsetof(struct pg_conn, load_balance_hosts)},
+
 	/* Terminating entry --- MUST BE LAST */
 	{NULL, NULL, NULL, NULL,
 	NULL, NULL, 0}
@@ -435,6 +441,8 @@ static void pgpassfileWarning(PGconn *conn);
 static void default_threadlock(int acquire);
 static bool sslVerifyProtocolVersion(const char *version);
 static bool sslVerifyProtocolRange(const char *min, const char *max);
+static bool parse_int_param(const char *value, int *result, PGconn *conn,
+							const char *context);
 
 
 /* global variable because fe-auth.c needs to access it */
@@ -1020,6 +1028,31 @@ parse_comma_separated_list(char **startptr, bool *more)
 	return p;
 }
 
+/*
+ * Initializes the prng_state field of the connection. We want something
+ * unpredictable, so if possible, use high-quality random bits for the
+ * seed. Otherwise, fall back to a seed based on the connection address,
+ * timestamp and PID.
+ */
+static void
+libpq_prng_init(PGconn *conn)
+{
+	if (unlikely(!pg_prng_strong_seed(&conn->prng_state)))
+	{
+		uint64		rseed;
+		struct timeval tval = {0};
+
+		gettimeofday(&tval, NULL);
+
+		rseed = ((uint64) conn) ^
+			((uint64) getpid()) ^
+			((uint64) tval.tv_usec) ^
+			((uint64) tval.tv_sec);
+
+		pg_prng_seed(&conn->prng_state, rseed);
+	}
+}
+
 /*
  *		connectOptions2
  *
@@ -1619,6 +1652,49 @@ connectOptions2(PGconn *conn)
 	else
 		conn->target_server_type = SERVER_TYPE_ANY;
 
+	/*
+	 * validate load_balance_hosts option, and set load_balance_type
+	 */
+	if (conn->load_balance_hosts)
+	{
+		if (strcmp(conn->load_balance_hosts, "disable") == 0)
+			conn->load_balance_type = LOAD_BALANCE_DISABLE;
+		else if (strcmp(conn->load_balance_hosts, "random") == 0)
+			conn->load_balance_type = LOAD_BALANCE_RANDOM;
+		else
+		{
+			conn->status = CONNECTION_BAD;
+			libpq_append_conn_error(conn, "invalid %s value: \"%s\"",
+									"load_balance_hosts",
+									conn->load_balance_hosts);
+			return false;
+		}
+	}
+	else
+		conn->load_balance_type = LOAD_BALANCE_DISABLE;
+
+	if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+	{
+		libpq_prng_init(conn);
+
+		/*
+		 * This is the "inside-out" variant of the Fisher-Yates shuffle
+		 * algorithm. Notionally, we append each new value to the array and
+		 * then swap it with a randomly-chosen array element (possibly
+		 * including itself, else we fail to generate permutations with the
+		 * last integer last).  The swap step can be optimized by combining it
+		 * with the insertion.
+		 */
+		for (i = 1; i < conn->nconnhost; i++)
+		{
+			int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+			pg_conn_host temp = conn->connhost[j];
+
+			conn->connhost[j] = conn->connhost[i];
+			conn->connhost[i] = temp;
+		}
+	}
+
 	/*
 	 * Resolve special "auto" client_encoding from the locale
 	 */
@@ -2626,6 +2702,32 @@ keep_going:						/* We will come back to here until there is
 		if (ret)
 			goto error_return;	/* message already logged */
 
+		/*
+		 * If random load balancing is enabled we shuffle the addresses.
+		 */
+		if (conn->load_balance_type == LOAD_BALANCE_RANDOM)
+		{
+			/*
+			 * This is the "inside-out" variant of the Fisher-Yates shuffle
+			 * algorithm. Notionally, we append each new value to the array
+			 * and then swap it with a randomly-chosen array element (possibly
+			 * including itself, else we fail to generate permutations with
+			 * the last integer last).  The swap step can be optimized by
+			 * combining it with the insertion.
+			 *
+			 * We don't need to initialize conn->prng_state here, because that
+			 * already happened in connectOptions2.
+			 */
+			for (int i = 1; i < conn->naddr; i++)
+			{
+				int			j = pg_prng_uint64_range(&conn->prng_state, 0, i);
+				AddrInfo	temp = conn->addr[j];
+
+				conn->addr[j] = conn->addr[i];
+				conn->addr[i] = temp;
+			}
+		}
+
 		reset_connection_state_machine = true;
 		conn->try_next_host = false;
 	}
@@ -4320,6 +4422,7 @@ freePGconn(PGconn *conn)
 	free(conn->outBuffer);
 	free(conn->rowBuf);
 	free(conn->target_session_attrs);
+	free(conn->load_balance_hosts);
 	termPQExpBuffer(&conn->errorMessage);
 	termPQExpBuffer(&conn->workBuffer);
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 7d091475255..d93e976ca57 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -26,7 +26,8 @@
 #include <netdb.h>
 #include <sys/socket.h>
 #include <time.h>
-#ifndef WIN32
+/* MinGW has sys/time.h, but MSVC doesn't */
+#ifndef _MSC_VER
 #include <sys/time.h>
 #endif
 
@@ -82,6 +83,8 @@ typedef struct
 #endif
 #endif							/* USE_OPENSSL */
 
+#include "common/pg_prng.h"
+
 /*
  * POSTGRES backend dependent Constants.
  */
@@ -242,6 +245,13 @@ typedef enum
 	SERVER_TYPE_PREFER_STANDBY_PASS2	/* second pass - behaves same as ANY */
 } PGTargetServerType;
 
+/* Target server type (decoded value of load_balance_hosts) */
+typedef enum
+{
+	LOAD_BALANCE_DISABLE = 0,	/* Use the existing host order (default) */
+	LOAD_BALANCE_RANDOM,		/* Randomly shuffle the hosts */
+} PGLoadBalanceType;
+
 /* Boolean value plus a not-known state, for GUCs we might have to fetch */
 typedef enum
 {
@@ -398,6 +408,7 @@ struct pg_conn
 	char	   *ssl_max_protocol_version;	/* maximum TLS protocol version */
 	char	   *target_session_attrs;	/* desired session properties */
 	char	   *require_auth;	/* name of the expected auth method */
+	char	   *load_balance_hosts; /* load balance over hosts */
 
 	/* Optional file to write trace info to */
 	FILE	   *Pfdebug;
@@ -469,6 +480,8 @@ struct pg_conn
 
 	/* Transient state needed while establishing connection */
 	PGTargetServerType target_server_type;	/* desired session properties */
+	PGLoadBalanceType load_balance_type;	/* desired load balancing
+											 * algorithm */
 	bool		try_next_addr;	/* time to advance to next address/host? */
 	bool		try_next_host;	/* time to advance to next connhost[]? */
 	int			naddr;			/* number of addresses returned by getaddrinfo */
@@ -488,6 +501,8 @@ struct pg_conn
 	PGVerbosity verbosity;		/* error/notice message verbosity */
 	PGContextVisibility show_context;	/* whether to show CONTEXT field */
 	PGlobjfuncs *lobjfuncs;		/* private state for large-object access fns */
+	pg_prng_state prng_state;	/* prng state for load balancing connections */
+
 
 	/* Buffer for data received from backend and not yet processed */
 	char	   *inBuffer;		/* currently allocated buffer */
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index 3cd0ddb4945..80e6a15adf8 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -116,6 +116,8 @@ tests += {
     'tests': [
       't/001_uri.pl',
       't/002_api.pl',
+      't/003_load_balance_host_list.pl',
+      't/004_load_balance_dns.pl',
     ],
     'env': {'with_ssl': ssl_library},
   },
diff --git a/src/interfaces/libpq/t/003_load_balance_host_list.pl b/src/interfaces/libpq/t/003_load_balance_host_list.pl
new file mode 100644
index 00000000000..6963ef38499
--- /dev/null
+++ b/src/interfaces/libpq/t/003_load_balance_host_list.pl
@@ -0,0 +1,81 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+# This tests load balancing across the list of different hosts in the host
+# parameter of the connection string.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $node1 = PostgreSQL::Test::Cluster->new('node1');
+my $node2 = PostgreSQL::Test::Cluster->new('node2', own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# Start the tests for load balancing method 1
+my $hostlist = $node1->host . ',' . $node2->host . ',' . $node3->host;
+my $portlist = $node1->port . ',' . $node2->port . ',' . $node3->port;
+
+$node1->connect_fails(
+	"host=$hostlist port=$portlist load_balance_hosts=doesnotexist",
+	"load_balance_hosts doesn't accept unknown values",
+	expected_stderr => qr/invalid load_balance_hosts value: "doesnotexist"/);
+
+# load_balance_hosts=disable should always choose the first one.
+$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=disable",
+	"load_balance_hosts=disable connects to the first node",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+# Statistically the following loop with load_balance_hosts=random will almost
+# certainly connect at least once to each of the nodes. The chance of that not
+# happening is so small that it's negligible: (2/3)^50 = 1.56832855e-9
+foreach my $i (1 .. 50) {
+	$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random",
+		"repeated connections with random load balancing",
+		sql => "SELECT 'connect1'");
+}
+
+my $node1_occurences = () = $node1->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node2_occurences = () = $node2->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node3_occurences = () = $node3->log_content() =~ /statement: SELECT 'connect1'/g;
+
+my $total_occurences = $node1_occurences + $node2_occurences + $node3_occurences;
+
+ok($node1_occurences > 1, "received at least one connection on node1");
+ok($node2_occurences > 1, "received at least one connection on node2");
+ok($node3_occurences > 1, "received at least one connection on node3");
+ok($total_occurences == 50, "received 50 connections across all nodes");
+
+$node1->stop();
+$node2->stop();
+
+# load_balance_hosts=disable should continue trying hosts until it finds a
+# working one.
+$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=disable",
+	"load_balance_hosts=disable continues until it connects to the a working node",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+# Also with load_balance_hosts=random we continue to the next nodes if previous
+# ones are down. Connect a few times to make sure it's not just lucky.
+foreach my $i (1 .. 5) {
+	$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=random",
+		"load_balance_hosts=random continues until it connects to the a working node",
+		sql => "SELECT 'connect4'",
+		log_like => [qr/statement: SELECT 'connect4'/]);
+}
+
+done_testing();
diff --git a/src/interfaces/libpq/t/004_load_balance_dns.pl b/src/interfaces/libpq/t/004_load_balance_dns.pl
new file mode 100644
index 00000000000..f914916dd24
--- /dev/null
+++ b/src/interfaces/libpq/t/004_load_balance_dns.pl
@@ -0,0 +1,124 @@
+# Copyright (c) 2023, PostgreSQL Global Development Group
+use strict;
+use warnings;
+use Config;
+use PostgreSQL::Test::Utils;
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+if ($ENV{PG_TEST_EXTRA} !~ /\bload_balance\b/)
+{
+	plan skip_all =>
+	  'Potentially unsafe test load_balance not enabled in PG_TEST_EXTRA';
+}
+
+# This tests loadbalancing based on a DNS entry that contains multiple records
+# for different IPs. Since setting up a DNS server is more effort than we
+# consider reasonable to run this test, this situation is instead immitated by
+# using a hosts file where a single hostname maps to multiple different IP
+# addresses. This test requires the adminstrator to add the following lines to
+# the hosts file (if we detect that this hasn't happend we skip the test):
+#
+# 127.0.0.1 pg-loadbalancetest
+# 127.0.0.2 pg-loadbalancetest
+# 127.0.0.3 pg-loadbalancetest
+#
+# Windows or Linux are required to run this test because these OSes allow
+# binding to 127.0.0.2 and 127.0.0.3 addresess by default, but other OSes
+# don't. We need to bind to different IP addresses, so that we can use these
+# different IP addresses in the hosts file.
+#
+# The hosts file needs to be prepared before running this test. We don't do it
+# on the fly, because it requires root permissions to change the hosts file. In
+# CI we set up the previously mentioned rules in the hosts file, so that this
+# load balancing method is tested.
+
+# Cluster setup which is shared for testing both load balancing methods
+my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os;
+
+# Checks for the requirements for testing load balancing method 2
+if (!$can_bind_to_127_0_0_2) {
+	plan skip_all => 'load_balance test only supported on Linux and Windows';
+}
+
+my $hosts_path;
+if ($windows_os) {
+	$hosts_path = 'c:\Windows\System32\Drivers\etc\hosts';
+}
+else
+{
+	$hosts_path = '/etc/hosts';
+}
+
+my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path);
+
+my $hosts_count = () = $hosts_content =~ /127\.0\.0\.[1-3] pg-loadbalancetest/g;
+if ($hosts_count != 3) {
+	# Host file is not prepared for this test
+	plan skip_all => "hosts file was not prepared for DNS load balance test"
+}
+
+$PostgreSQL::Test::Cluster::use_tcp = 1;
+$PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1';
+my $port = PostgreSQL::Test::Cluster::get_free_port();
+my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port);
+my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1);
+my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1);
+
+# Create a data directory with initdb
+$node1->init();
+$node2->init();
+$node3->init();
+
+# Start the PostgreSQL server
+$node1->start();
+$node2->start();
+$node3->start();
+
+# load_balance_hosts=disable should always choose the first one.
+$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=disable",
+	"load_balance_hosts=disable connects to the first node",
+	sql => "SELECT 'connect2'",
+	log_like => [qr/statement: SELECT 'connect2'/]);
+
+
+# Statistically the following loop with load_balance_hosts=random will almost
+# certainly connect at least once to each of the nodes. The chance of that not
+# happening is so small that it's negligible: (2/3)^50 = 1.56832855e-9
+foreach my $i (1 .. 50) {
+	$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random",
+		"repeated connections with random load balancing",
+		sql => "SELECT 'connect1'");
+}
+
+my $node1_occurences = () = $node1->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node2_occurences = () = $node2->log_content() =~ /statement: SELECT 'connect1'/g;
+my $node3_occurences = () = $node3->log_content() =~ /statement: SELECT 'connect1'/g;
+
+my $total_occurences = $node1_occurences + $node2_occurences + $node3_occurences;
+
+ok($node1_occurences > 1, "received at least one connection on node1");
+ok($node2_occurences > 1, "received at least one connection on node2");
+ok($node3_occurences > 1, "received at least one connection on node3");
+ok($total_occurences == 50, "received 50 connections across all nodes");
+
+$node1->stop();
+$node2->stop();
+
+# load_balance_hosts=disable should continue trying hosts until it finds a
+# working one.
+$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=disable",
+	"load_balance_hosts=disable continues until it connects to the a working node",
+	sql => "SELECT 'connect3'",
+	log_like => [qr/statement: SELECT 'connect3'/]);
+
+# Also with load_balance_hosts=random we continue to the next nodes if previous
+# ones are down. Connect a few times to make sure it's not just lucky.
+foreach my $i (1 .. 5) {
+	$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=random",
+		"load_balance_hosts=random continues until it connects to the a working node",
+		sql => "SELECT 'connect4'",
+		log_like => [qr/statement: SELECT 'connect4'/]);
+}
+
+done_testing();
diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 3e2a27fb717..a3aef8b5e91 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -2567,6 +2567,22 @@ sub issues_sql_like
 	return;
 }
 
+=pod
+
+=item $node->log_content()
+
+Returns the contents of log of the node
+
+=cut
+
+sub log_content
+{
+	my ($self) = @_;
+	return
+	  PostgreSQL::Test::Utils::slurp_file($self->logfile);
+}
+
+
 =pod
 
 =item $node->run_log(...)
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index dfa1e309ee3..86a3f8160fa 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1704,6 +1704,7 @@ PGFileType
 PGFunction
 PGLZ_HistEntry
 PGLZ_Strategy
+PGLoadBalanceType
 PGMessageField
 PGModuleMagicFunction
 PGNoticeHooks
-- 
2.34.1