Add helper function for reading values by field name

The helper function provides map-like access to row values. This is used
to retrieve the values for all MariaDB 10.0+ versions as there are
differences in the returned results between 10.1 and 10.2.

include/maxscale/mysql_utils.h

@@ -66,6 +66,17 @@ int mxs_mysql_query(MYSQL* conn, const char* query);
  */
 bool mxs_mysql_trim_quotes(char *s);
 
+/**
+ * Helper function for getting values by field name
+ *
+ * @param result Resultset
+ * @param row    Row where the value is read
+ * @param key    Name of the field
+ *
+ * @return The value of the field or NULL if value is not found. NULL values
+ *         are also returned as NULL pointers.
+ */
+const char* mxs_mysql_get_value(MYSQL_RES* result, MYSQL_ROW row, const char* key);
 
 typedef enum mxs_pcre_quote_approach
 {

server/core/mysql_utils.cc

@@ -23,6 +23,7 @@
 #include <maxscale/mysql_utils.h>
 
 #include <string.h>
+#include <strings.h>
 #include <stdbool.h>
 #include <errmsg.h>
 
@@ -210,6 +211,22 @@ int mxs_mysql_query(MYSQL* conn, const char* query)
     return rc;
 }
 
+const char* mxs_mysql_get_value(MYSQL_RES* result, MYSQL_ROW row, const char* key)
+{
+    MYSQL_FIELD* f = mysql_fetch_fields(result);
+    int nfields = mysql_num_fields(result);
+
+    for (int i = 0; i < nfields; i++)
+    {
+        if (strcasecmp(f[i].name, key) == 0)
+        {
+            return row[i];
+        }
+    }
+
+    return NULL;
+}
+
 bool mxs_mysql_trim_quotes(char *s)
 {
     bool dequoted = true;

server/modules/monitor/mysqlmon/mysql_mon.cc

@@ -1089,22 +1089,22 @@ static bool do_show_slave_status(MYSQL_SERVER_INFO* serv_info, MXS_MONITORED_SER
 
                 if (server_version == MYSQL_SERVER_VERSION_100)
                 {
-                    ss_debug(MYSQL_FIELD* f = mysql_fetch_fields(result));
+                    const char* beats = mxs_mysql_get_value(result, row, "Slave_received_heartbeats");
-                    ss_dassert(strcmp(f[MARIA10_STATUS_HEARTBEATS].name, "Slave_received_heartbeats") == 0);
+                    const char* period = mxs_mysql_get_value(result, row, "Slave_heartbeat_period");
-                    ss_dassert(strcmp(f[MARIA10_STATUS_HEARTBEAT_PERIOD].name, "Slave_heartbeat_period") == 0);
+                    const char* gtid = mxs_mysql_get_value(result, row, "Gtid_Slave_Pos");
-                    ss_dassert(strcmp(f[MARIA10_STATUS_SLAVE_GTID].name, "Gtid_Slave_Pos") == 0);
+                    ss_dassert(beats && period);
 
-                    int heartbeats = atoi(row[MARIA10_STATUS_HEARTBEATS]);
+                    int heartbeats = atoi(beats);
                     if (serv_info->slave_heartbeats < heartbeats)
                     {
                         serv_info->latest_event = time(NULL);
                         serv_info->slave_heartbeats = heartbeats;
-                        serv_info->heartbeat_period = atof(row[MARIA10_STATUS_HEARTBEAT_PERIOD]);
+                        serv_info->heartbeat_period = atof(period);
                     }
 
-                    if (row[MARIA10_STATUS_SLAVE_GTID])
+                    if (gtid)
                     {
-                        extract_slave_gtid(serv_info, row[MARIA10_STATUS_SLAVE_GTID]);
+                        extract_slave_gtid(serv_info, gtid);
                     }
                 }