From 6357f49f867765d62a8a4398733194c07561281a Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@sraoss.co.jp>
Date: Mon, 3 May 2021 20:04:38 +0900
Subject: [PATCH] Allow to build pgpool with PostgreSQL 9.0 or before.

pool_process_reporting.c referrers to PQpingParams() which was
introduced in PostgreSQL 9.1. Check existence of the function in
configure and if it does not exist, set "pg_status" column of "show
pool_nodes" and "pcp_node_info" to be set "unknown".
---
 configure.ac                           |  1 +
 doc.ja/src/sgml/ref/pcp_node_info.sgml |  6 ++++--
 doc/src/sgml/ref/pcp_node_info.sgml    | 15 ++++++++++-----
 src/utils/pool_process_reporting.c     |  6 ++++++
 4 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/configure.ac b/configure.ac
index f550f5d17..22c79ae5a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -429,6 +429,7 @@ LDFLAGS="-L$PGSQL_LIB_DIR $LDFLAGS"
 OLD_LIBS="$LIBS"
 AC_CHECK_LIB(pq, PQexecPrepared, [], [AC_MSG_ERROR(libpq is not installed or libpq is old)])
 AC_CHECK_FUNCS(PQprepare)
+AC_CHECK_FUNCS(PQpingParams)
 LDFLAGS="$OLD_LDFLAGS"
 LIBS="$OLD_LIBS"
 
diff --git a/doc.ja/src/sgml/ref/pcp_node_info.sgml b/doc.ja/src/sgml/ref/pcp_node_info.sgml
index 18c9a66e1..cf3b692c9 100644
--- a/doc.ja/src/sgml/ref/pcp_node_info.sgml
+++ b/doc.ja/src/sgml/ref/pcp_node_info.sgml
@@ -166,8 +166,10 @@ Pgpool-II documentation
   </para>
   <para>
    6は実際のバックエンドの状態をリアルタイムで取得して表示します。
-   情報の取得は<command>pg_isready</command>を呼び出すことによって行われます。
-   <xref linkend="pcp-detach-node">でバックエンドノードを切り離すと、<productname>Pgpool-II</productname>が管理する状態は"Down"になりますが、バックエンドの実際の状態は"up"なので、5と6が一致しないことはあり得ます。
+   情報の取得は、このコマンドが実行された時に<function>PQpingParams</function>を呼び出すことによって行われます。
+   <function>PQpingParams</function>は<productname>PostgreSQL</productname> 9.1以降でのみサポートされています。
+   <productname>Pgpool-II</productname>が<productname>PostgreSQL</productname> 9.0以前とともに構築されると、この列は"unknown"と表示します。
+   <xref linkend="pcp-detach-node">でバックエンドノードを切り離すと、<productname>Pgpool-II</productname>が管理する状態は"down"になりますが、バックエンドの実際の状態は"up"なので、5と6が一致しないことはあり得ます。
     逆に、5が"up"なのに、6が"down"というのは起こらないはずです。
   </para>
   <para>
diff --git a/doc/src/sgml/ref/pcp_node_info.sgml b/doc/src/sgml/ref/pcp_node_info.sgml
index a29f411bd..3ad2a0021 100644
--- a/doc/src/sgml/ref/pcp_node_info.sgml
+++ b/doc/src/sgml/ref/pcp_node_info.sgml
@@ -80,7 +80,7 @@ Pgpool-II documentation
     3. status
     4. load balance weight
     5. status name
-    6. actual backend status (taken from pg_isready. Pgpool-II 4.3 or later)
+    6. actual backend status
     7. backend role
     8. actual backend role (taken from pg_is_in_recovery. Pgpool-II 4.3 or later)
     9. replication delay
@@ -120,10 +120,15 @@ Pgpool-II documentation
      </itemizedlist>
   </para>
   <para>
-   6 shows the backend status in real time.  The info is taken by
-   calling <command>pg_isready</command>.  When a backend node is
-   detached by <xref linkend="pcp-detach-node">, the status managed by
-   <productname>Pgpool-II</productname> will be "Down", while the
+   6 shows the backend status in real time.  The info is obtained by
+   calling <function>PQpingParams</function> at the time when the
+   command is invoked. <function>PQpingParams</function> is only
+   available in <productname>PostgreSQL</productname> 9.1 or later. If
+   <productname>Pgpool-II</productname> was built with
+   <productname>PostgreSQL</productname> 9.0 or earlier, the column
+   shows "unknown". When a backend node is detached by <xref
+   linkend="pcp-detach-node">, the status managed by
+   <productname>Pgpool-II</productname> will be "down", while the
    actual backend status is "up". Thus it is possible that 5 does not
    match with 6. However it should not happen that 5 is "up" while 6
    is "down".
diff --git a/src/utils/pool_process_reporting.c b/src/utils/pool_process_reporting.c
index 0187bc33a..429864b0f 100644
--- a/src/utils/pool_process_reporting.c
+++ b/src/utils/pool_process_reporting.c
@@ -2170,6 +2170,7 @@ static void write_one_field_v2(POOL_CONNECTION * frontend, char *field)
 static
 char *db_node_status(int node)
 {
+#ifdef HAVE_PQPINGPARAMS
 	BackendInfo *bkinfo;
 	int		i;
 	char	portstr[32];
@@ -2177,6 +2178,7 @@ char *db_node_status(int node)
 	const char *keywords[PARAMS_ARRAY_SIZE];
 	const char *values[PARAMS_ARRAY_SIZE];
 	PGPing	ret;
+#endif
 
 	/*
 	 * If health check is not enabled, return "unknown".
@@ -2186,6 +2188,7 @@ char *db_node_status(int node)
 		return "unknown";
 	}
 
+#ifdef HAVE_PQPINGPARAMS
 	i = 0;
 	
 	keywords[i] = "user";
@@ -2221,6 +2224,9 @@ char *db_node_status(int node)
 		return "up";
 	}
 	return "down";
+#else
+	return "unknown";
+#endif
 }
 
 /*
-- 
2.39.5