repmgr: initialise "voting_term" in "repmgr primary register"

This previously happened in the extension SQL code, which could
potentially cause replay problems if installing on a BDR cluster.

As this table is only required for streaming replication failover,
move the initialisation to "repmgr primary register".

Addresses GitHub #344 .

dbutils.c

@@ -3735,7 +3735,7 @@ int
 get_current_term(PGconn *conn)
 {
 	PGresult   *res = NULL;
-	int term = -1;
+	int term = VOTING_TERM_NOT_SET;
 
 	res = PQexec(conn, "SELECT term FROM repmgr.voting_term");
 
@@ -3747,13 +3747,43 @@ get_current_term(PGconn *conn)
 		return -1;
 	}
 
-	term = atoi(PQgetvalue(res, 0, 0));
+	if (PQntuples(res) > 0)
+	{
+		term = atoi(PQgetvalue(res, 0, 0));
+	}
 
 	PQclear(res);
 	return term;
 }
 
 
+void
+initialize_voting_term(PGconn *conn)
+{
+	PGresult   *res = NULL;
+
+	int current_term = get_current_term(conn);
+
+	if (current_term == VOTING_TERM_NOT_SET)
+	{
+		res = PQexec(conn, "INSERT INTO repmgr.voting_term (term) VALUES (1)");
+	}
+	else
+	{
+		res = PQexec(conn, "UPDATE repmgr.voting_term SET term = 1");
+	}
+
+	if (PQresultStatus(res) != PGRES_COMMAND_OK)
+	{
+		log_error(_("unable to initialize repmgr.voting_term:\n  %s"),
+				  PQerrorMessage(conn));
+	}
+
+	PQclear(res);
+	return;
+}
+
+
 void
 increment_current_term(PGconn *conn)
 {
@@ -3765,8 +3795,6 @@ increment_current_term(PGconn *conn)
 	{
 		log_error(_("unable to increment repmgr.voting_term:\n  %s"),
 				  PQerrorMessage(conn));
-		PQclear(res);
-		return;
 	}
 
 	PQclear(res);

dbutils.h

@@ -473,6 +473,7 @@ bool		delete_monitoring_records(PGconn *primary_conn, int keep_history);
 
 
 /* node voting functions */
+void		initialize_voting_term(PGconn *conn);
 int			get_current_term(PGconn *conn);
 void		increment_current_term(PGconn *conn);
 bool		announce_candidature(PGconn *conn, t_node_info *this_node, t_node_info *other_node, int electoral_term);

repmgr--4.0.sql

@@ -91,9 +91,6 @@ CREATE RULE voting_term_delete AS
    ON DELETE TO repmgr.voting_term
    DO INSTEAD NOTHING;
 
-/* XXX do this in "repmgr primary register" */
-INSERT INTO repmgr.voting_term (term) VALUES (1);
-
 
 /* ================= */
 /* repmgrd functions */

repmgr-action-primary.c

@@ -74,7 +74,11 @@ do_primary_register(void)
 
 	log_verbose(LOG_INFO, _("server is not in recovery"));
 
-	/* create the repmgr extension if it doesn't already exist */
+	/*
+	 * create the repmgr extension if it doesn't already exist;
+	 * note that create_repmgr_extension() will take into account
+	 * the --dry-run option
+	 */
 	if (!create_repmgr_extension(conn))
 	{
 		PQfinish(conn);
@@ -92,6 +96,7 @@ do_primary_register(void)
 		return;
 	}
 
+	initialize_voting_term(conn);
 
 	/* Ensure there isn't another registered node which is primary */
 	primary_conn = get_primary_connection(conn, &current_primary_id, NULL);

repmgr.h

@@ -56,6 +56,7 @@
 #define NO_UPSTREAM_NODE	-1
 #define UNKNOWN_NODE_ID		-1
 
+#define VOTING_TERM_NOT_SET -1
 
 /*
  * various default values - ensure repmgr.conf.sample is update